2.Principles of modern classification of microbes.
Microbes or microorganisms(bacteria, fungi, protozoa, viruses), systematized according to their similarities, differences and relationships with each other. This is done by a special science - taxonomy of microorganisms, which includes three parts: classification, taxonomy and identification. The taxonomy of microorganisms is based on their morphological, physiological, biochemical and molecular biological properties. The following taxonomic categories are distinguished: kingdom, subkingdom, department, class, order, family, genus, species, subspecies, etc. Within a particular taxonomic category, taxa are distinguished - groups of organisms united by certain homogeneous properties.
Microorganisms are represented by precellular forms (viruses - kingdom Vira) and cellular forms (bacteria, archaebacteria, fungi and protozoa). There are 3 domains:
□ domain “Bacteria” - prokaryotes, represented by real bacteria (eubacteria);
□ domain “Archaea” - prokaryotes, represented by archaebacteria;
□ “Eukarya” domain - eukaryotes, whose cells have a nucleus with a nuclear envelope and nucleolus, and the cytoplasm consists of highly organized organelles - mitochondria, Golgi apparatus, etc. The “Eukarya” domain includes: the kingdom Fungi (fungi); animal kingdom Animalia (includes protozoa - subkingdom Protozoa); plant kingdom Plante. Domains include kingdoms, phyla, classes, orders, families, genera, and species.
View. One of the main taxonomic categories is species. A species is a collection of individuals united by similar properties, but differing from other representatives of the genus.
Pure culture. A set of homogeneous microorganisms isolated on a nutrient medium, characterized by similar morphological, tinctorial (relation to dyes), cultural, biochemical and antigenic properties, is called a pure culture.
Strain. A pure culture of microorganisms isolated from a specific source and different from other members of the species is called a strain. A strain is a narrower concept than a species or subspecies.
Clone. Close to the concept of a strain is the concept of a clone. A clone is a collection of descendants grown from a single microbial cell.
To designate certain collections of microorganisms that differ in certain properties, the suffix var (variety) is used instead of the previously used type.
Biovariant –
Serovariant –
Phagovariant –
3.Basic methods for studying the morphology of bacteria .
Morphological properties of bacteria. Bacteria are microorganisms that do not have a formed nucleus (prokaryotes).
Bacteria have a diverse shape and a rather complex structure, which determines the diversity of their functional activities. Bacteria are characterized by four main shapes: spherical (spherical), cylindrical (rod-shaped), convoluted and filamentous.
spherical bacteria- cocci - depending on the plane of division and the location of individual individuals relative to each other, they are divided into micrococci (separate cocci), diplococci (paired cocci), streptococci (chains of cocci), staphylococci (grape-shaped), tetracocci (formations of four cocci ) and sarcina (packets of 8 or 16 cocci).
Rod-shaped bacteria are located in the form of single cells, diplo- or streptobacteria.
Twisted shapes of bacteria- vibrios and spirilla, as well as spirochetes. Vibrios have the appearance of slightly curved rods, spirilla have a convoluted shape with several spiral curls.
Sizes of bacteria range from 0.1 to 10 microns. The composition of a bacterial cell includes a capsule, a cell wall, a cytoplasmic membrane and cytoplasm, which contains a nucleoid, ribosomes and inclusions. Some bacteria are equipped with flagella and villi. A number of bacteria form spores that are located terminally, subterminally or centrally; Exceeding the transverse size of the cell, the spores give it a spindle-shaped shape.
Painting methods. The smear is stained using simple or complex methods. Simple ones involve coloring the preparation with one dye; complex methods (according to Gram, Ziehl-Nielsen, etc.) include the sequential use of several dyes and have differential diagnostic value. The relationship of microorganisms to dyes is regarded as tinctorial properties. There are special staining methods that are used to identify flagella, cell walls, nucleoids, and various cytoplasmic inclusions.
microscopic method: light, phase-contrast, fluorescent, electronic;
cultural method (bacteriological, virological);
biological method (infection of laboratory animals);
molecular genetic method (PCR - polymerase chain reaction)
serological method - identifying antigens of microorganisms or antibodies to them;
Complex Methods staining is used to study cell structure and differentiation of microorganisms. Stained smears are examined microscopically in an immersion system. Consistently apply certain dyes, differing in chemical composition and color, mordants, alcohols, acids, etc. to the preparation.
Cell wall stained according to the Peshkov method - the prepared and dried preparation is placed in Carnoy’s liquid (a mixture of ethyl alcohol, chloroform and glacial acetic acid, 6:3:1) for 15 minutes, washed with water, etched in a 10% tannin solution for 6-8 minutes, washed, stain with water fuchsin for 30 seconds, dry.
Capsule according to Burri-Gins
Associated with this file 20
file(s). Among them: lecture feeding young cattle3Word.docx, feeding pigsWord.docx, Tischenko_Tango.pdf, Khachaturyan_Cello_part.pdf, cello_part_Bach__Brandenburg_Concerto.pdf, Anxiety disorders in neurology.ppt.ppt, Brain injuries.pptx.pptx, Toxic lesions of the nervous system PPT. ppt, Medical microbiology.doc and 10 more file(s).
Show all linked files
1 2 3 4 5 6 7 8 9 … 60
1. Basics of microbiology
Microbiology as an independent science , which has its own objects and research methods, was formed in the second half of the 19th century thanks to the work Pasteur,Koch, Erlich, Mechnikov, Ru etc., but also at the present time, as well as those closely related to it, biotechnology And Genetic Engineering , is constantly and intensively developing.
Originating as science ofpathogens , i.e. as a branch of medicine, to date depending on the tasks being solveddivided by :
· industrial;
· agricultural;
· veterinary;
· sanitary;
· medical microbiology.
Subject studying medical microbiology are microorganisms — representatives of the normal microflora of the human body and pathogens of various human diseases, and laboratory diagnostic methods, specific prevention And etiotropic therapy the diseases they cause.
2. Classification (systematics) of microorganisms
Microorganisms — This organisms, invisible to the naked eye due to their small size. This criterion is the only one that unites them. Otherwise, the world of microorganisms is even more diverse than the world of macroorganisms. According to modern taxonomy, microorganisms belong tothree kingdoms:
· Vira- these include viruses;
· Eucariotae- these include protozoa and fungi;
· Procariotae- these include true bacteria, rickettsia, chlamydia,
mycoplasmas, spirochetes, actinomycetes.
Main differences prokaryote from eukaryotes are that prokaryotes do not have :
· morphologically designed kernels(No nuclear membrane and missing nucleolus), its equivalent is nucleoid, or genophore , representing closed circular double-stranded DNA molecule, attached at one point to the cytoplasmic membrane; by analogy with eukaryotes, this molecule is called a chromosomal bacterium;
· Golgi reticular apparatus;
· endoplasmic reticulum;
· mitochondria.
There is also a number of signs or organelles, characteristic of many, but not all prokaryotes, which allow distinguish them from eukaryotes :
· numerous invagination of the cytoplasmic membrane which are called mesosomes , they are associated with the nucleoid and participate in cell division, sporulation, And respiration of a bacterial cell;
· specific cell wall component— murein , according to the chemical structure it is peptidoglycan(diaminopiemic acid);
· plasmids — autonomously replicating circular double-stranded DNA molecules with a molecular weight smaller than that of a bacterial chromosome. They are located along with the nucleoid in the cytoplasm, although they can be integrated into it and carry hereditary information, which is not vital for a microbial cell, but providing her this or that selective advantages in the environment. Most famous plasmids :
— (F-plasmids), providing conjugative transfer between bacteria;
— (R-plasmids)— drug resistance plasmids, which ensure circulation among bacteria of genes that determine resistance to chemotherapeutic agents used to treat various diseases.
Just like for plants and animals, it is used to name microorganisms. binary nomenclature , - that is generic and species name, but if researchers cannot determine the species and only the genus is determined, then the term “species” is used. Most often this occurs when identifying microorganisms with non-traditional nutritional needs or living conditions.
Name sort of usually either based on the morphological characteristic of the corresponding microorganism (for example, Staphylococcus, Vibrio, Mycobacterium) or are derived from the name of the author who discovered or studied the pathogen (for example, Neisseria, Shigella, Escherichia, Rickettsia, Gardnerella).
Species the name is often associated with the name of the main disease caused by this microorganism (for example, Vibrio cholerae - cholera, Shigella dysenteriae - dysentery, Mycobacterium tuberculosis - tuberculosis) or with the main habitat (for example, Escherihia coli - E. coli).
In addition, in Russian-language medical literature it is possible to use the corresponding Russified name of bacteria (for example, instead of Staphylococcus epidermidis - epidermal staphylococcus; Staphylococcus aureus - Staphylococcus aureus, etc.).
Kingdom of prokaryotes includes department of cyanobacteria And department of eubacteria, which, in turn, subdivided into orders :
· bacteria themselves (divisions Gracilicutes, Firmicutes, Tenericutes, Mendosicutes);
· actinomycetes;
· spirochete;
· rickettsia;
· chlamydia.
Bacteria - This prokaryotic, mainly unicellular microorganisms, which can Also form associations(groups) similar cells, characterized cellular, but not organismic similarities.
Orders are divided into groups. Main taxonomic criteria , allowing one to assign bacterial strains to one or another group, are :
· morphology of microbial cells (cocci, rods, convoluted);
· relation to Gram staining - tinctorial properties (gram-positive and gram-negative);
· type of biological oxidation - aerobes, facultative anaerobes, obligate anaerobes;
· ability to form spores.
Further differentiation of groups on families, genera and species, that are main taxonomic category, is carried out on the basis studying biochemical properties V. This principle is the basis classification of bacteria given in special manuals — determinants of bacteria .
View is an evolutionarily established set of individuals having a single genotype, which under standard conditions manifests itself with similar morphological, physiological, biochemical signs. For pathogenic bacteria the definition of “species” is supplemented by the ability to cause certain nosological forms of diseases. There is intraspecific differentiation of bacteria into options:
· according to biological properties (biovars or biotypes);
· by biochemical activity (enzyme products);
· by antigenic structure (serovars or serotypes);
· according to sensitivity to bacteriophages (phagevars or phagetypes);
· on antibiotic resistance (resistant products).
In microbiology, special terms are widely used - culture, strain, clone.
Culture - This a collection of bacteria visible to the eye on nutrient media. Cultures can be clean () And mixed (a collection of bacteria of two or more species).
Strain - This a collection of bacteria of the same species, allocated from different sources or from the same source at different times. Strains may differ in some characteristics that do not go beyond the characteristics of the species.
Clone - This a collection of bacteria that are the offspring of a single cell.
1 2 3 4 5 6 7 8 9 … 60
go to file directory
Systematics of microorganisms.
Page 1 of 26Next ⇒
Taxonomy- distribution of microorganisms according to their origin and biological similarity.
Taxonomy deals with a comprehensive description species organisms, clarifying the degree of related relationships between them and combining them into classification units of different levels of relatedness - taxa. The main issues resolved during taxonomy (three aspects, three pillars of taxonomy) - classification, identification and nomenclature.
Classification- distribution (association) of organisms in accordance with their common properties (similar genotypic and phenotypic characteristics) among various taxa.
Taxonomy- the science of methods and principles of distribution (classification) of organisms in accordance with their hierarchy.
The most commonly used taxonomic units (taxa) are: strain, species, genus. Subsequent larger taxa - family, order, class.
In modern terms species in microbiology
It is based on the use of the maximum number of comparable characteristics and mathematical consideration of the degree of correspondence.
Gram stain.
substrates
autotrophs, heterotrophs), nitrogen ( .
8.Ability to sporulation, the nature of the dispute.
In recent decades, for the classification of microorganisms, in addition to their phenotypic characteristics (see.
1-12), various genetic methods are being used more and more widely and effectively (study of genotype- genotypic properties).
Medical microbiology. Medical microbiology
Identification.
Nomenclature-
Strain serotypes (serovariants- abbreviated serovars) phagotypes, biochemical properties - chemovars biovars etc.
The colony- a visible isolated structure when bacteria multiply on solid nutrient media; it can develop from one or more parent cells.
If a colony develops from one parent cell, then the offspring is called clone.
Culture
crops.
Morphology of bacteria.
.
µm) x 2-3 microns.
2. Rod-shaped.
3.Crimped.
4. Thread-like.
Coccus bacteria (cocci)
1.Micrococci.
2.Diplococci.
3.Streptococci.
4.Tetracocci. Division in two mutually perpendicular planes with the formation of tetrads (i.e. four cells).
They have no medical significance.
5.Sarcins. Division in three mutually perpendicular planes, forming bales (packages) of 8, 16 or more cells. Often found in the air.
6.Staphylococcus(from Latin - bunch of grapes).
They divide randomly in different planes, forming clusters resembling bunches of grapes. They cause numerous diseases, primarily purulent-inflammatory ones.
2. Bacilli are aerobic spore-forming microbes.
The diameter of the spore usually does not exceed the size (“width”) of the cell (endospore).
It must be kept in mind that the term “bacteria” is often used to refer to all prokaryotic microbes. In a narrower (morphological) sense, bacteria are rod-shaped forms of prokaryotes that do not have spores.
Main groups of bacteria Genera of bacteria
sliding-
Cabbage bacteria
spirochetes Borrelia, Leptospira
eubacteria
myces, Nocardia, Strep-
B. Simple unicellular
2/free living
gram-positive:
cocci Streptococcus, Staphy-
teria, Erysipelothrix
spore-forming rods
b. gram negative:
cocci Neisseria
non-coliform bacteria
incl. spiral shaped Spirillum
Yersinia, Francisella,
Haemophilus, Borde-
coli
facultative anaerobes Escherichia, Salmone-
lla, Shigella, Klebsiel-
la, Proteus, Vibrio
12345678910Next ⇒
Read also:
Classification, or taxonomy of microorganisms (from the Greek Systematikos - ordered, systematized), is a branch of microbiology that deals with the creation of a classification of microorganisms based on their properties and related relationships.
2. Systematics and nomenclature of microorganisms
The term “taxonomy” is sometimes used as a synonym for the concept of “taxonomy of microorganisms.”
Currently, there is no universal, only correct, classification.
Depending on the task at hand, microorganisms can be classified according to morphological characteristics (rods, cocci, convoluted, etc.), according to tinctorial characteristics (gram-positive, gram-negative, etc.), according to physiological characteristics (thermophilic , psychrophilic, acidophilic, aerobic, etc.), according to environmental characteristics (nitrogen-fixing, nitrifying, sulfate-reducing, cellulose-destroying, etc.), according to interspecific relationships (antagonists, synnergists, commensals, etc.), according to taxis species, genotypic and phylogenetic characteristics.
Microorganisms are also classified according to the degree of danger to humans, animals and the environment. Thus, the classification of microorganisms is a subjective processing of objective characteristics.
Modern taxonomy of microorganisms includes three main areas:
Characteristics of microorganisms— obtaining all possible information about the properties and parameters necessary to classify the microorganisms being determined to a particular taxon.
Classification or taxonomy, i.e. the process of orderly arrangement of microorganisms into taxonomic groups based on similarity.
3. Nomenclature— assignment of scientific names to taxonomic groups (taxa).
The main taxonomic unit in the taxonomy of microorganisms is view.
According to general biological concepts, a species is a group of closely related organisms that have a common root of origin and, at a given stage of evolution, are characterized by certain morphological, biochemical and physiological characteristics, isolated by selection from other species and adapted to a specific habitat. An important species characteristic is the ability of organisms to interbreed and produce offspring.
The definition of a species in bacteria is fundamentally different from the classical definition of a biological species, since they do not have a sexual method of reproduction.
According to modern concepts, closely related organisms with a 70% level of DNA homology and a similar set of morphological, biochemical and physiological characteristics are classified as one type of bacteria.
The following taxonomic categories are also used in the hierarchical classification of microorganisms: subspecies- a group of closely related similar organisms within type with a DNA homology level above 70%; genus- a taxonomic group that unites related species, and further - family, suborder, order, subclass, class, kingdom And domain(or superkingdom).
Currently, families and domains have been described to a greater extent, while the remaining taxonomic groups are in the process of systematization.
Domains are the highest taxa of microorganisms, corresponding to the previously distinguished kingdoms. According to the modern classification, the entire diversity of microorganisms is represented by three domains: Bacteria (prokaryotic microorganisms, true bacteria), Archaea (another evolutionary branch of prokaryotic microorganisms) and Eukarya (eukaryotic microorganisms)(rice.
2). Of these, two domains (Bacteria and Archaea) include only representatives of prokaryotes, which are separated into a separate superkingdom — Procariolae.
Fig.2. Universal phylogenetic tree of living organisms.
The most accurate, informative and easy-to-use classification system is one in which taxa are defined based on a variety of consistent characteristics obtained using various modern methods.
This approach to identifying taxa is called polyphasic.
The main methods of modern polyphasic taxonomy are: genotypic, phenotypic and phylogenetic.
The genotypic method is dominant in polyphasic taxonomy.
It is based on the study of the C+G composition of DNA, on the study of DNA-rRNA homology, on the establishment of related relationships between microorganisms that are encoded in the nucleotide sequences of the 16S or 23S rRNA genes. For example, when determining whether a microorganism belongs to a certain species, the level of similarity of DNA nucleotide sequences of about 70% plays a primary role. Therefore, the genotypic method is often called the genomic fingerprinting method.
Phenotypic studies are most often used in various schemes for identifying microorganisms, for the formal description of a taxon, from variety and subspecies to genus and family.
While genotypic data are necessary to place a taxon on a phylogenetic tree and classification system, phenotypic characterization provides descriptive information that allows the identification of a particular microorganism species. Classic phenotypic characteristics include morphological, physiological, biochemical, chemotaxonomic and serological characteristics of microorganisms.
Morphological characteristics indicate what size and shape the microorganism has (coccus, rod, spirilla), whether it has a capsule or spores, whether the cells are united in chains, tetrads or packets, whether they have flagella and how they are located, whether they are colored Gram cells.
Bacterial morphology includes the study of cultural properties, i.e. growth pattern on nutrient media, shape of colonies on solid nutrient media, pigment formation.
Physiological features characterize the mechanism of metabolism, the method of obtaining energy, the ability of a given microorganism to transform certain substances, its relationship to carbon, nitrogen, oxygen, temperature, pH of the environment.
Biochemical characteristics are determined by the ability of microorganisms to decompose certain sugars, form hydrogen sulfide, ammonia and other compounds.
Chemotaxonomic features characterize the chemical composition of the cell cytoplasm.
Taxonomic specificity of the composition of fatty acids, lipoproteins, lipopolysaccharides, pigments, polyamines, proteins and other chemical components of the cell is widely used in the classification of microorganisms.
Serological properties, or serotyping, are based on identifying the variability of the antigenic components of bacterial cells.
Such components can be flagella and fimbriae. capsules, cell wall, enzymes and toxins. To identify the antigenic properties of a bacterial cell, various serological reactions are used: precipitation reaction, complement adhesion reaction, precipitation, etc.
Thus, phenotypic characteristics are characterized by a large volume and variety of information obtained, which is difficult to process manually.
There was a need for computer, numerical analysis of the data obtained. A numeric (numerical) taxonomy has appeared, which makes it possible to analyze the phenotypic and genotypic characteristics of microorganisms using computer programs. The use of numeric analysis in taxonomic practice is called “computer identification.”
Phylogenetic methods (from the Greek phylon - genus, tribe and genesis - origin, occurrence) allow us to trace the process of historical development of microorganisms both as a whole and their individual taxonomic groups: species, subspecies, genera, families, suborders, orders , subclasses, classes, kingdoms and domains.
Phylogenetic relationships between microorganisms are studied using the methods of genomic fingerprinting, molecular biology, and computer identification.
Based on the data obtained, phylogenetic trees are constructed that reflect the evolutionary relationships between microorganisms (Fig. 3). The created phylogenetic trees cannot be used to construct a hierarchical classification of microorganisms and do not replace taxonomy. They are one of its elements.
Nomenclature— deals with issues of accurate and uniform names. This is a system of names used in a certain field of knowledge.
In accordance with international rules, names are assigned to taxonomic groups of microorganisms.
Even before the introduction of the first rules of nomenclature, a huge number of microorganisms were described. Moreover, the same bacterium could be classified into taxa with different names. To avoid this, the International Code of Nomenclature defined all priority names of bacteria published since May 1, 1753. As a result, the “List of Recognized Names of Bacteria” was created, which came into force on January 1, 1980.
Currently, the name of microorganisms is assigned in accordance with the rules of the International Code of Nomenclature of Bacteria. The competence of the Code extends only to the rules for assigning and using scientific names of microorganisms. Classification issues are resolved independently of the Code on the basis of ongoing taxonomic studies.
3. Phylogenetic tree of bacteria.
In microbiology, as in biology, a double (binary) nomenclature was adopted to designate bacterial species, proposed back in 1760 by Carl Linnaeus.
The first word denotes the name of the genus. Usually this is a Latin word, it is written with a capital letter and characterizes some morphological or physiological characteristic, or the name of the scientist who discovered this microbe. For example, the genus “Pasteurella” is named after the French scientist L. Pasteur, the genus “Salmonella” is named after the American microbiologist Salmon, the genus “Salmonella” is named after the German scientist T.
Escherich - the genus "Escherichia", the Japanese microbiologist Shiga - the genus "Shigella", the English bacteriologists D. Bruce and S. Erwin - the genera "Brucella" and "Erwinia", the Russian scientists Kuznetsov and Lyambl - the genera "Kuznetsovia" and "Liamblia" and etc. The name of the genus of a microorganism is usually shortened to one or two letters.
The second word denotes the specific epithet in the name of the microorganism and, as a rule, is a derivative of a noun that describes the color of the colony, the source of the microorganism, the process or disease it causes.
The name of the species is written with a lowercase letter and is never abbreviated. For example, Escherichia coli means that Escherichia lives in the intestines, Pasterella pestis means pasteurella that causes plague, Bordetetia pertussis means bordetella that causes cough, Clostridium tetani means clostridia that causes tetanus, etc.
Winogradsky and M. Beijerink, taking into account the diversity of bacterial metabolism, proposed that the genus name reflect characteristics associated with the morphology, ecology, biochemistry and physiology of microorganisms. This is how the names appeared, which are the key to the characteristics of the microorganism: Acetobacter (acid-forming bacteria), Nitrosomonas (nitrifying bacteria), Azotobakter (bacteria that fix atmospheric nitrogen), Chromobakterium (pigmented bacteria), V.
stearothermophiliis (waxy heat-loving bacteria), etc.
Sometimes it is considered as an integral part of taxonomy identification(definition) of microorganisms. However, this is not entirely correct, since identification uses already constructed classification systems and specific characteristics of microorganisms indicated in identification keys (tables).
Microorganism identification schemes are a kind of test of the quality of the classification system. During the day of identification of microorganisms, phenotypic and genotypic methods, methods of computer identification analysis and genomic fingerprinting are widely used.
In 1923 D.
Bergey released the first international identification of bacteria. Subsequent editions were prepared by the International Committee on the Taxonomy of Bacteria. The ninth and final American edition of Bergey's Manual of Determinative Bacteriology was published in 1994. The abbreviated name of the Manual is BMDB-9. The Russian translation of BMDB-9 was published in 1997.
It introduces the diversity of prokaryotes and takes a step forward in attempts to identify microorganisms isolated from the environment.
According to BMDB-9, bacteria are divided (according to phenotypic characteristics) into four main categories:
1. Gram-negative eubacteria with cell walls.
2. Gram-positive eubacteria with cell walls.
Eubacteria lacking cell walls.
4. Archaebacteria.
The main object in identifying microorganisms is a pure culture of an isolated bacterium, called a “strain” or “clone”.
Strain(from German.
stammen - to occur) is a bacterial culture of the same species, isolated from different objects or from the same object at different times, and characterized by minor changes in properties (for example, sensitivity to antibiotics, enzymatic activity, ability to form toxins ). Typically, strains of the same species are adapted to a specific environment.
Under the term " bacterial culture» understand the population of microbial cells in a given place and at a given time.
These can be microorganisms grown on a solid or liquid nutrient medium in a laboratory. A culture of microorganisms grown on a solid or liquid nutrient medium from individuals of one species by successive subcultures of a single colony is called clean.
Pure bacterial cultures obtained from one original cell are called clones(from Greek
klon - offspring). A clone is a genetically homogeneous population.
A mixed culture is a culture of heterogeneous microorganisms isolated from the material being studied, for example, from water, soil, air.
Date of publication: 2015-11-01; Read: 4841 | Page copyright infringement
studopedia.org - Studopedia.Org - 2014-2018 (0.003 s)…
Taxonomy is a science that deals with the classification (distribution) of microorganisms into groups (taxa) in accordance with certain characteristics, their nomenclature and identification. A taxon is a group of organisms that have a given degree of homogeneity.
The basic taxonomic unit in biology is the species. View is an evolutionarily established set of individuals of the same genotype, possessing similar morphological, physiological, cultural, biochemical and other characteristics.
Species in microbiology are divided into subspecies or variants, strains and clones. Bacteria options differ in their individual characteristics: morphological (morphovars), biological (biovars), enzymatic (enzymevars), resistance to antibiotics (resistancevars) and bacteriophages (phagevars), antigenic structure (serovars), pathogenicity for certain hosts (pathovars).
Strain is a microbial culture isolated from a specific source (human, animal, environmental) by different authors and at different times.
Taxonomy of bacteria
Clone- a culture of microorganisms obtained from one individual. Under the term "culture" understand microorganisms grown on a liquid or solid nutrient medium.
There are two principles of taxonomy: phylogenetic, which is based on the establishment of related relationships between organisms (taxonomy of higher organisms) and practical(artificial), the purpose of which is to identify the degree of similarity between microorganisms for quick identification and assignment to certain taxa.
The modern taxonomy of microorganisms is based on the following characteristics:
Morphological:-shape, Gram stain, motility, spore and capsule formation, size;
2. Biochemical: type of metabolism, fermentation of sugars and polyhydric alcohols, proteolytic properties, etc.
3. Physiological: attitude to sources of C, O, nitrogen, temperature, pH, humidity;
Cultural characteristics: growth pattern on solid and liquid media;
5. Molecular biological(features of DNA structure).
Currently, the international taxonomy of bacteria according to Bergi is accepted. Bergey is an American scientist who headed the school of microbiologists, who, under his leadership, compiled a taxonomy of prokaryotes. Its first edition (“Manual of the taxonomy of bacteria”) was published in 1923, the ninth – 1st volume in 1984, 2nd volume – in 1986, 3rd volume – in 1989.
According to this taxonomy, depending on the structure of the cell wall, all prokaryotes are divided into 4 sections:
Gracilicutes(gracilis - thin, slender, cutes - skin). All gram-negative microorganisms are included in the department.
2. Firmicutes- (firmis - strong, durable). The department includes gram-positive cocci, rods and threads.
3. Tenericute s - (tenes - soft, gentle).
The section includes mycoplasmas that lack a cell wall.
4. Mendosicutes(mendosi - imperfect cell wall). Microorganisms that do not contain murein and live in extreme conditions are included - methane-forming, sulfur-oxidizing, halophilic, thermoacidophilic, etc.
After the division come the following taxa: class, group(or section), order(suffix - ales), family(-ceae), genus, species.
In microbiology, the binomial nomenclature proposed by K. Linnaeus is used: the first word denotes the genus and is written with a capital letter, the second is the species name and is written with a small letter.
The name of the genus includes some morphological, physiological characteristics or the name of the author who studied this genus. The species name is a description of the colony (color, shape) or source of origin.
Date of publication: 2014-11-29; Read: 3259 | Page copyright infringement
studopedia.org - Studopedia.Org - 2014-2018 (0.001 s)…
The taxonomy of microorganisms is extremely complex. Many microorganisms have the same morphological characteristics, but different physiological properties. The evolution of many microorganisms is unknown, and the relationships between them are often unclear. In addition, the concept of “species” for microorganisms still does not have a clear definition. Typically, microorganisms that have common morphological and physiological properties and are similar in antigenic structure are classified as one species.
In their habitat, the microorganisms that make up this species cause similar processes as a result of their vital activity. The species name for microorganisms is given according to the binomial (double) nomenclature proposed by Linnaeus in 1760.
1. Taxonomy of microorganisms.
The first word in the name of a microorganism means the genus and is usually Latin, the second word is the specific name of the microbe. The genus name is written with a capital letter, and the species name with a lowercase letter, for example Bacillus anthracis - anthrax bacillus, the causative agent of anthrax.
When writing, the generic name of a bacterium is usually abbreviated to the initial letter, for example E. coli (Escherichia coli) - Escherichia coli.
The names of microorganisms may reflect the names of the scientists who discovered them. Thus, Brucella was described by the English scientist Bruce, Giardia by the Russian doctor Lambl. The genus “Salmonella” is named after the American microbiologist Salmon, the genus “Escherichia” is named after the German scientist Escherich, and the genus “Shigella” is named after the Japanese microbiologist Shiga.
Sometimes the name of microorganisms is associated with the name of the organ that they affect: for example, meningococci cause damage to the meninges, pneumococci cause damage to the lungs, etc. These names do not comply with the rules of nomenclature.
Taxonomy of microorganisms
Taxonomy is the distribution of microorganisms according to their origin and biological similarity. Systematics deals with a comprehensive description of species of organisms, elucidation of the degree of related relationships between them and their unification into classification units of different levels of relatedness - taxa.
The main issues addressed in taxonomy (three aspects, three pillars of taxonomy) are classification, identification and nomenclature. In other words, the main goal of taxonomy is to identify the microorganism. Classification is the distribution (association) of organisms in accordance with their common properties (similar genotypic and phenotypic characteristics) into various taxa.
Taxonomy is the science of methods and principles of distribution (classification) of organisms in accordance with their hierarchy.
The most commonly used taxonomic units (taxa) are strain, species, genus. Subsequent larger taxa - family, order, class. In modern terms species in microbiology- a set of microorganisms that have a common evolutionary origin, a close genotype (a high degree of genetic homology, usually more than 60%) and the closest possible phenotypic characteristics.
Numerical (numerical) taxonomy is based on the use of the maximum number of comparable characteristics and mathematical consideration of the degree of correspondence.
The large number of compared phenotypic characteristics and the principle of their equal importance made classification difficult.
When studying, identifying and classifying microorganisms, the following (geno- and phenotypic) characteristics are most often studied:
1. Morphological - shape, size, features of relative position, structure.
2. Tinctorial - relation to various dyes (nature of staining), primarily to Gram staining.
On this basis, all microorganisms are divided into gram-positive and gram-negative.
Morphological properties and relation to Gram staining make it possible, as a rule, to classify the microorganism under study as a large taxon - family, genus.
3. Cultural - the nature of the growth of a microorganism on nutrient media.
4. Biochemical - the ability to ferment various substrates(carbohydrates, proteins and amino acids, etc.), form various biochemical products in the process of life due to the activity of various enzyme systems and metabolic characteristics.
Antigenic - depend primarily on the chemical composition and structure of the cell wall, the presence of flagella, capsules, are recognized by the ability of the macroorganism (host) to produce antibodies and other forms of immune response, are detected in immunological reactions.
Physiological - methods of carbohydrate (autotrophs, heterotrophs), nitrogen (aminoautotrophs, aminoheterotrophs) and other types of nutrition, type of respiration (aerobes, microaerophiles, facultative anaerobes, strict anaerobes).
7. Mobility and types of movement.
8. Ability to form spores, nature of spores.
9. Sensitivity to bacteriophages, phage typing.
10. Chemical composition of cell walls - basic sugars and amino acids, lipid and fatty acid composition.
Protein spectrum (polypeptide profile).
12. Sensitivity to antibiotics and other drugs.
13. Genotypic (use of genosystematic methods).
Classification of microorganisms
Classification of microorganisms (root taxon) is the distribution of microorganisms according to similar or distinctive characteristics into ordered groups.
Classification of microorganisms is one of the most difficult sections of microbiology.
The more complete our information about organisms, the more accurately we classify them.
The modern classification of microorganisms is based on a hierarchical principle. Different levels of the hierarchy (taxonomic categories, series, ranks) have their own names (from highest to lowest): kingdom, department, class, order, family, genus, species.
It is accepted that any given microorganism must consistently belong to all 7 categories.
Kingdom (lat.
regnum) is a hierarchical level of the scientific classification of microorganisms, the taxon of the highest level among the main ones. Historically, there are five kingdoms of living organisms: animals; plants; mushrooms; bacteria; viruses. Since 1977, two more kingdoms have been added to them: protists; archaea. Since 1998, another one has been distinguished: chromists.
Division (lat. dvisio) is one of the highest ranks of the taxonomic hierarchy in microbiology. In the hierarchy of taxonomic categories, a division is above a class and below a kingdom.
The names of departments, like the names of other taxa whose rank is higher than the genus, are uninomial, that is, they consist of one word - a noun, or an adjective used as a noun, in the plural, written with a capital letter. Class (lat.
classis) is one of the main ranks of hierarchical classification in biological systematics. In the hierarchy of systematic categories, class is below department and above order. Class names, like the names of other taxa whose rank is higher than genus, are uninomial. Order (lat. ordo) is one of the main ranks of hierarchical classification. In the hierarchy of systematic categories it stands below class and above family. In bacteriology, the standardized ending –ales is used to name orders.
Carl Linnaeus expressed the opinion that “order is a division of classes, introduced in order not to differentiate more genera than the mind can easily perceive.” Family (lat.
familia) one of the main ranks of hierarchical classification in biological systematics. In the hierarchy of systematic categories, family is lower than order and higher than genus. Family names are formed according to the rules governed by the International Code of Nomenclature of Bacteria. The family name is derived from the name of the type genus, to the stem of which the standard ending aceae is added.
Genus (lat. genus) is one of the main ranks of hierarchical classification in biological systematics.
In the hierarchy of systematic categories, genus is below family and above species. The scientific name of the genus is uninomial, that is, it consists of one word. Codes of biological nomenclature require that this word be in Latin form, that is, written in letters of the Latin alphabet and subject to the rules of Latin grammar.
The genus name is treated as a singular noun and is written with a capital letter. There are no other restrictions, so the genus name can be either a word borrowed from classical Latin or a Latinized word from any language (most often from ancient Greek). Often the genus name is a word derived from a surname or given name (for example, Escherichia) from the name of the scientist Escherich.
From the stem of the generic name the names of the taxa of the family group are formed. The rules for the formation and application of generic names are established by the rules set forth in the International Code of Nomenclature of Bacteria. Species (lat. species) is a taxonomic, systematic unit, a group of individuals with common morphophysiological, biochemical and behavioral characteristics, capable of mutual crossing, producing fertile offspring in a number of generations, naturally distributed within a certain area and similarly changing under the influence of environmental factors.
A species is a really existing unit of the living world, the main structural unit in a system of organisms. In the classification of microorganisms, the problem of species is the most important and difficult. Without defining the species, it is impossible to build a classification.
A species is a collection of microorganisms that have the same origin and genotype, and similar morphological and biological properties.
The species of bacteria is determined by the sum of various characteristics and properties and is a product of the evolution of living matter, which has its own history of development, formation and stabilization as a result of adaptation to the conditions of existence. Pure culture is a collection of homogeneous microorganisms isolated on a nutrient medium, which are characterized by similar biological properties.
A strain is a pure culture of a microorganism, isolated from a specific source, and different from other representatives of the species.
A clone is a collection of descendants grown from a single microbial cell.
In modern classifications, any sign is used, as long as it stands out and makes it possible to recognize the microorganism being studied. The concept of a superkingdom, or biological domain, is relatively new.
It was proposed in 1990 by Carl Woese and introduced the division of all Earth's biomass into three domains:
1) eukaryotes (a domain that unites all organisms whose cells contain a nucleus);
2) bacteria;
3) archaea.
Based on the structural features of microorganisms and other single-celled organisms, they are divided into two clearly distinct groups: eukaryotes and prokaryotes.
Eukaryotes are higher microorganisms, or protists.
Their cells are similar in structure to plant and animal cells. Eukaryotes include algae, fungi and protozoa. Eukaryotic cells have a differentiated nucleus, delimited from the cytoplasm by a nuclear membrane. Inside the nucleus there is a set of chromosomes, which, doubling during the process of division - mitosis, are passed on to daughter cells. The cytoplasm of eukaryotes contains a developed endoplasmic reticulum, originating from the cytoplasmic membrane, as well as mitochondria and various organelles - plastids.
Prokaryotes are lower protists.
These include bacteria and blue-green algae. Prokaryotes are very different in structure from all other living organisms. In the cell wall of prokaryotes, peptidoglycans (glycoproteins) were found that were not found in eukaryotic cells. The nucleus of a prokaryotic cell is not differentiated: deoxyriboucleic acid (DNA), which makes up the chromosome, is freely immersed in the cytoplasm, the nuclear envelope is absent. The endoplasmic reticulum is poorly developed, so division into “compartments” in the cytoplasm is not pronounced.
There is still no uniform international classification of microorganisms. Fungi, protozoa and viruses have their own specific classification, which will be described in the relevant sections.
There are also different classification schemes for bacteria and blue-green algae. Currently, Burgee's taxonomy, set out in the “Definition of Bacteria,” last published in 1974, is increasingly recognized. It describes and systematizes more than 1,500 species of microorganisms related to prokaryotes.
Microorganisms related to prokaryotes are divided into two sections: I - cyanobacteria (blue-green algae) and II - bacteria. The department of bacteria is described and systematized in the most detail. It includes, in addition to the bacteria themselves (cocci, rods, spirilla), microorganisms such as spirochetes, actinomycetes, rickettsia, chlamydia, mycoplasma. The department of bacteria is divided into 19 groups or parts, which correspond to subdivisions or subclasses.
These groups include orders, families, genera and species that are of great importance to humans. Among the microorganisms that cause human diseases are: spirochetes (group 5), gonococci, staphylococci, streptococci (groups 10 and 14), pathogens of intestinal infections, including cholera (group 8), pathogens of anaerobic infections and anthrax (group 15 ), actinomycetes and mycobacteria (group 17), rickettsia and chlamydia (group 18), mycoplasma (group 19).
Identification of microorganisms
The basic phenotypic and genotypic characteristics used to classify microorganisms are also used for identification, i.e. establishing their taxonomic position and, above all, species, is the most important aspect of the microbiological diagnosis of infectious diseases. Identification is carried out on the basis of studying the pheno- and genotypic characteristics of the infectious agent being studied and comparing them with the characteristics of known species.
In this work, reference strains of microorganisms, standard antigens, and immune sera are often used against known prototype microorganisms. In pathogenic microorganisms, morphological, tinctorial, cultural, biochemical and antigenic properties are often studied.
Nomenclature - the name of microorganisms in accordance with international rules.
To designate bacterial species, the binary Latin nomenclature genus/species is used, consisting of the name of the genus (written with a capital letter) and the species (written with a lowercase letter). Examples: Shigella flexneri, Rickettsia sibirica.
In microbiology, a number of other terms are often used to characterize microorganisms.
In microbiology, there are also the concepts of “strain” and “clone”.
Strain - microorganisms of one type, isolated simultaneously from one source: from a patient or carrier, as well as from environmental objects (from water, food products, household items). Strains differ from each other in certain characteristics, for example, resistance to antibiotics, sulfonamides, and the ability to cause infectious diseases of varying severity, clinical course and outcome. However, strains of one species have all the characteristics that characterize them as a species.
They also retain their specific name, to which they add the initial letters of the surname or initials of the patients from whom the strain was isolated, or the name of the territory in which it was discovered. For example, different strains of the influenza virus are named after the place where they were isolated: the “Asian” strain of the influenza virus, the “Hong Kong” strain of the influenza virus.
Clone is a culture of microorganisms obtained by multiplying one cell of a given species or strain.
The term “culture” or “population” is used to designate a collection of microbes growing on a nutrient medium from one or several cells of the same species (from the French population - population). A population of microbes consisting of individuals of one species is called a pure culture, and a population of individuals of different species is called a mixed culture.
The basic principle of bacteriological work is isolating and studying the properties of only pure(homogeneous, without admixture of foreign microflora) crops.
1 2 3 4 5 6 7 8 9 10
Numerical (numerical) taxonomy is based on the use of the maximum number of compared characteristics and mathematical consideration of the degree of correspondence. The large number of compared phenotypic characteristics and the principle of their equal importance made classification difficult.
When studying, identifying and classifying microorganisms, the following (geno- and phenotypic) characteristics are most often studied:
1. Morphological - shape, size, features of relative position, structure.
2. Tinctorial - attitude to various dyes (nature of coloring), primarily to Gram stain.
On this basis, all microorganisms are divided into gram-positive and gram-negative.
Morphological properties and relation to Gram staining make it possible, as a rule, to classify the microorganism under study as a large taxon - family, genus.
3. Cultural - the nature of the growth of the microorganism on nutrient media.
4.Biochemical - ability to ferment various substrates(carbohydrates, proteins and amino acids, etc.), form various biochemical products in the process of life due to the activity of various enzyme systems and metabolic characteristics.
5. Antigenic - depend mainly on the chemical composition and structure of the cell wall, the presence of flagella, capsules, are recognized by the ability of the macroorganism (host) to produce antibodies and other forms of immune response, are detected in immunological reactions.
6. Physiological methods of carbohydrate ( autotrophs, heterotrophs), nitrogen ( aminoautotrophs, aminoheterotrophs) and other types of nutrition, type of breathing ( aerobes, microaerophiles, facultative anaerobes, strict anaerobes).
7.Mobility and types of movement.
8.Ability to sporulation, the nature of the dispute.
9. Sensitivity to bacteriophages, phage typing.
10. Chemical composition of cell walls - basic sugars and amino acids, lipid and fatty acid composition.
11. Protein spectrum (polypeptide profile).
12. Sensitivity to antibiotics and other drugs.
13. Genotypic (use of genosystematic methods).
In recent decades, to classify microorganisms, in addition to their phenotypic characteristics (see paragraphs 1-12), various genetic methods (study of genotype - genotypic properties). More and more advanced methods are used - restriction analysis, DNA-DNA hybridization, PCR, sequencing, etc.
Most methods are based on the principle of determining the degree of homology of genetic material (DNA, RNA). In this case, they often proceed from the conditional assumption that the degree of homology of more than 60% (for some groups of microorganisms - 80%) indicates that the microorganisms belong to the same species (different genotypes - one genotype), 40-60% - to the same genus.
Identification.
The basic phenotypic and genotypic characteristics used to classify microorganisms are also used for identification, i.e.
establishing their taxonomic position and, above all, species, is the most important aspect of the microbiological diagnosis of infectious diseases. Identification is carried out on the basis of studying the pheno- and genotypic characteristics of the infectious agent being studied and comparing them with the characteristics of known species.
In this work, reference strains of microorganisms, standard antigens, and immune sera are often used against known prototype microorganisms. In pathogenic microorganisms, morphological, tinctorial, cultural, biochemical and antigenic properties are often studied.
Nomenclature- name of microorganisms in accordance with international rules.
To designate bacterial species, the binary Latin nomenclature genus/species is used, consisting of the name of the genus (written with a capital letter) and the species (written with a lowercase letter). Examples: Shigella flexneri, Rickettsia sibirica.
In microbiology, a number of other terms are often used to characterize microorganisms.
Strain- any specific sample (isolate) of a given species. Strains of the same species that differ in antigenic characteristics are called serotypes (serovariants- abbreviated serovars), according to sensitivity to specific phages - phagotypes, biochemical properties - chemovars, according to biological properties - biovars etc.
The colony- a visible isolated structure when bacteria multiply on solid nutrient media; it can develop from one or more parent cells. If a colony develops from one parent cell, then the offspring is called clone.
Culture- the entire collection of microorganisms of the same species grown on a solid or liquid nutrient medium.
The basic principle of bacteriological work is isolating and studying the properties of only pure(homogeneous, without admixture of foreign microflora) crops.
Morphology of bacteria.
Prokaryotes differ from eukaryotes in a number of basic characteristics.
1. Absence of a true differentiated nucleus (nuclear membrane).
2. Lack of developed endoplasmic reticulum and Golgi apparatus.
3. Absence of mitochondria, chloroplasts, lysosomes.
4. Inability to endocytosis (capture food particles).
5. Cell division is not associated with cyclic changes in cell structure.
Significantly smaller sizes (usually). Most bacteria are 0.5-0.8 micrometers in size ( µm) x 2-3 microns.
Based on their shape, the following main groups of microorganisms are distinguished.
1. Globular or cocci (from Greek - grain).
2. Rod-shaped.
3.Crimped.
4. Thread-like.
Coccus bacteria (cocci)by the nature of the relationship after division they are divided into a number of options.
1.Micrococci.
The cells are located alone. They are part of the normal microflora and are found in the external environment. They do not cause diseases in humans.
2.Diplococci. The division of these microorganisms occurs in one plane, pairs of cells are formed. Among diplococci there are many pathogenic microorganisms - gonococcus, meningococcus, pneumococcus.
3.Streptococci. Division is carried out in one plane, the multiplying cells maintain connection (do not diverge), forming chains.
There are many pathogenic microorganisms that cause sore throats, scarlet fever, and purulent inflammatory processes.
4.Tetracocci. Division in two mutually perpendicular planes with the formation of tetrads (i.e. four cells). They have no medical significance.
5.Sarcins.
Division in three mutually perpendicular planes, forming bales (packages) of 8, 16 or more cells. Often found in the air.
6.Staphylococcus(from Latin - bunch of grapes). They divide randomly in different planes, forming clusters resembling bunches of grapes.
They cause numerous diseases, primarily purulent-inflammatory ones.
Rod-shaped microorganisms.
1. Bacteria are rods that do not form spores.
2. Bacilli are aerobic spore-forming microbes. The diameter of the spore usually does not exceed the size (“width”) of the cell (endospore).
3. Clostridia are anaerobic spore-forming microbes. The diameter of the spore is larger than the diameter (diameter) of the vegetative cell, causing the cell to resemble a spindle or tennis racket.
It must be kept in mind that the term “bacteria” is often used to refer to all prokaryotic microbes.
In a narrower (morphological) sense, bacteria are rod-shaped forms of prokaryotes that do not have spores.
Twisted forms of microorganisms.
1. Vibrios and campylobacters - have one bend, can be in the shape of a comma, a short curl.
2.Spirillas - have 2-3 curls.
3. Spirochetes - have a different number of whorls, an axostyle - a set of fibrils, a pattern of movement and structural features specific to different representatives (especially the terminal sections).
Of the large number of spirochetes, representatives of three genera are of greatest medical importance - Borrelia, Treponema, Leptospira.
Characteristics of the morphology of rickettsia, chlamydia, mycoplasmas, more detailed characteristics of vibrios and spirochetes will be given in the relevant sections of private microbiology.
We conclude this section with a brief description (key) for characterizing the main genera of microorganisms of medical importance, based on the criteria used in the Bergey identification of bacteria.
Key to the main groups of bacteria
Main groups of bacteria | Genera of bacteria
1.Bending bacteria with thin walls, mobile
performance is ensured by sliding - sliding-
living bacteria
2. Curving bacteria with thin walls, motile Treponema
ity is associated with the presence of axial filament spirochetes Borrelia, Leptospira
3.Rigid bacteria with thick walls, immobile
ny or mobile thanks to flagella - eubacteria
Mycelial forms of Mycobacterium, Actino-
myces, Nocardia, Strep-
B. Simple unicellular
2/free living
gram-positive:
cocci Streptococcus, Staphy-
non-spore-forming rods Corynebacterium, Lis-
teria, Erysipelothrix
spore-forming rods
incl. obligate aerobes Bacillus
incl. obligate anaerobes Clostridium
b. gram negative:
cocci Neisseria
non-coliform bacteria
spiral shaped Spirillum
incl. straight, very small sticks of Pasteurella, Brucella,
Yersinia, Francisella,
Haemophilus, Borde-
coli
incl. facultative anaerobes Escherichia, Salmone-
lla, Shigella, Klebsiel-
la, Proteus, Vibrio
incl. obligate aerobes Pseudomonas
incl. obligate anaerobes Bacteroides, Fuso-
4.Without cell walls Mycoplasma, Urea-
3.Structure of a bacterial cell.
The obligatory organelles are: nuclear apparatus, cytoplasm, cytoplasmic membrane.
Optional(minor) structural elements are: cell wall, capsule, spores, pili, flagella.
1.In the center of the bacterial cell is nucleoid- a nuclear formation, most often represented by one ring-shaped chromosome.
Systematics and classification of microorganisms
Consists of a double-stranded DNA strand. The nucleoid is not separated from the cytoplasm by the nuclear membrane.
2.Cytoplasm- a complex colloidal system containing various inclusions of metabolic origin (grains of volutin, glycogen, granulosa, etc.), ribosomes and other elements of the protein synthesizing system, plasmids (extranucleoid DNA), mesosomes(formed as a result of invagination of the cytoplasmic membrane into the cytoplasm, participate in energy metabolism, sporulation, and the formation of the intercellular septum during division).
3.Cytoplasmic membrane limits the cytoplasm on the outside, has a three-layer structure and performs a number of important functions - barrier (creates and maintains osmotic pressure), energy (contains many enzyme systems - respiratory, redox, carries out electron transfer), transport (transfer of various substances into the cell and from the cell).
4.Cell wall- is inherent in most bacteria (except for mycoplasmas, acholeplasmas and some other microorganisms that do not have a true cell wall).
It has a number of functions, primarily providing mechanical protection and a constant shape of cells; the antigenic properties of bacteria are largely associated with its presence. It consists of two main layers, of which the outer one is more plastic, the inner one is rigid.
The main chemical compound of the cell wall, which is specific only to bacteria - peptidoglycan(mureic acids). An important characteristic for taxonomy of bacteria depends on the structure and chemical composition of the bacterial cell wall - Relation to Gram stain.
In accordance with it, two large groups are distinguished: gram-positive (“gram +”) and gram-negative (“gram -”) bacteria. The wall of gram-positive bacteria after Gram staining retains the iodine complex with gentian violet(colored blue-violet), gram-negative bacteria lose this complex and the corresponding color after treatment and are colored pink due to staining with fuchsin.
Features of the cell wall of gram-positive bacteria.
A powerful, thick, uncomplicated cell wall, which is dominated by peptidoglycan and teichoic acids, no lipopolysaccharides (LPS), and often no diaminopimelic acid.
Features of the cell wall of gram-negative bacteria.
The cell wall is much thinner than that of gram-positive bacteria and contains LPS, lipoproteins, phospholipids, and diaminopimelic acid.
The structure is more complex - there is an outer membrane, so the cell wall is three-layered.
When gram-positive bacteria are treated with enzymes that destroy peptidoglycan, structures completely devoid of a cell wall appear - protoplasts.
Treatment of gram-negative bacteria with lysozyme destroys only the peptidoglycan layer, without completely destroying the outer membrane; such structures are called spheroplasts. Protoplasts and spheroplasts have a spherical shape (this property is associated with osmotic pressure and is characteristic of all cell-free forms of bacteria).
L-forms of bacteria.
Under the influence of a number of factors that adversely affect the bacterial cell (antibiotics, enzymes, antibodies, etc.), L— transformation bacteria, leading to permanent or temporary loss of the cell wall.
L-transformation is not only a form of variability, but also an adaptation of bacteria to unfavorable living conditions. As a result of changes in antigenic properties (loss of O- and K-antigens), a decrease in virulence and other factors, L-forms acquire the ability to remain for a long time ( persist) in the host’s body, maintaining a sluggish infectious process.
The loss of the cell wall makes L-forms insensitive to antibiotics, antibodies and various chemotherapy drugs, the point of application of which is the bacterial cell wall.
Unstable L-forms are capable reverse into classical (original) forms of bacteria that have a cell wall. There are also stable L-forms of bacteria, the absence of a cell wall and the inability to reverse into the classical forms of bacteria are genetically fixed.
In a number of ways, they are very similar to mycoplasmas and other Mollicutes- bacteria in which the cell wall is absent as a taxonomic feature. Microorganisms belonging to mycoplasmas are the smallest prokaryotes, do not have a cell wall and, like all bacterial wallless structures, have a spherical shape.
To the surface structures of bacteria(optional, like the cell wall), include capsule, flagella, microvilli.
Capsule or a mucous layer surrounds the membrane of a number of bacteria.
Highlight microcapsule, detected by electron microscopy in the form of a layer of microfibrils, and macrocapsule, detectable by light microscopy. The capsule is a protective structure (primarily from drying out), in a number of microbes it is a pathogenicity factor, prevents phagocytosis, and inhibits the first stages of protective reactions - recognition and absorption. U saprophytes capsules are formed in the external environment, in pathogens, more often in the host body. There are a number of methods for coloring capsules depending on their chemical composition.
The capsule often consists of polysaccharides (the most common color is Ginsu), less often from polypeptides.
Flagella. Motile bacteria can be gliding (move along a solid surface as a result of wave-like contractions) or floating, moving due to filament-like spirally curved proteins ( flagellinaceae by chemical composition) formations - flagella.
Based on the location and number of flagella, a number of forms of bacteria are distinguished.
1.Monotrichous - have one polar flagellum.
2. Lophotrichs - have a polarly located bundle of flagella.
3. Amphitrichy - have flagella at diametrically opposite poles.
4.Peritrichy - have flagella along the entire perimeter of the bacterial cell.
The ability for purposeful movement (chemotaxis, aerotaxis, phototaxis) in bacteria is genetically determined.
Fimbriae or cilia- short filaments, in large numbers surrounding the bacterial cell, with the help of which bacteria are attached to substrates (for example, to the surface of mucous membranes).
Thus, fimbriae are factors of adhesion and colonization.
F-pili (fertility factor)- apparatus bacterial conjugation, are found in small quantities in the form of thin protein fibers.
Endospores and sporulation.
Sporulation- a method of preserving certain types of bacteria in unfavorable environmental conditions.
Endospores are formed in the cytoplasm, are cells with low metabolic activity and high resistance ( resistance) to drying, chemical factors, high temperature and other unfavorable environmental factors. Light microscopy is often used to identify spores. according to Ozheshko. High resistance is associated with high content calcium salt of dipicolinic acid spores in the shell.
The location and size of spores in different microorganisms differs, which has differential diagnostic (taxonomic) significance. The main phases of the “life cycle” of spores sporulation(includes preparatory stage, prespore stage, shell formation, maturation and dormancy) and germination, ending with the formation of a vegetative form. The process of sporulation is genetically determined.
Unculturable forms of bacteria.
Many species of gram-negative bacteria that do not form spores have a special adaptive state - uncultivable forms.
They have low metabolic activity and do not actively reproduce, i.e. They do not form colonies on solid nutrient media and are not detected by culture. They are highly resistant and can remain viable for several years. Not detected by classical bacteriological methods, detected only using genetic methods ( polymerase chain reaction - PCR).
They are considered to be single-celled organisms whose size does not exceed 0.1 mm. Representatives of this large group may have different cellular organization, morphological characteristics and metabolic capabilities, that is, the main feature that unites them is size. The term “microorganism” itself is not endowed with a taxonomic meaning. Microbes belong to a wide variety of taxonomic units, and other members of these units can be multicellular and reach large sizes.
General approaches to the classification of microorganisms
As a result of the gradual accumulation of factual material about microbes, the need arose to introduce rules for their description and systematization.
The classification of microorganisms is characterized by the presence of the following taxa: domain, phylum, class, order, family, genus, species. In microbiology, scientists use a binomial system for characterizing an object, that is, the nomenclature includes the names of the genus and species.
Most microorganisms are characterized by an extremely primitive and universal structure; therefore, their division into taxa cannot be carried out only on the basis of morphological characteristics. Functional features, molecular biological data, patterns of biochemical processes, etc. are used as criteria.
Identification Features
To identify an unknown microorganism, studies are carried out to study the following properties:
- Cytology of cells (primarily belonging to pro- or eukaryotic organisms).
- Morphology of cells and colonies (in specific conditions).
- Cultural characteristics (growth characteristics on different media).
- A set of physiological properties on which the classification of microorganisms by type of respiration (aerobic, anaerobic) is based.
- Biochemical features (presence or absence of certain metabolic pathways).
- A set of molecular biological properties, including taking into account the nucleotide sequence, the possibility of hybridization of nucleic acids with the material of standard strains.
- Chemotaxonomic indicators, which involve taking into account the chemical composition of various compounds and structures.
- Serological characteristics (antigen-antibody reactions; especially for pathogenic microorganisms).
- The presence and nature of sensitivity to specific phages.
The taxonomy and classification of microorganisms belonging to prokaryotes is carried out using the Bergey Manual of Taxonomy of Bacteria. And identification is carried out using the Bergey determinant.
Different ways to classify microbes
To determine the taxonomic affiliation of an organism, several methods of classifying microorganisms are used.
In a formal numerical classification, all features are considered equally significant. That is, the presence or absence of a particular feature is taken into account.
Morphophysiological classification implies the study of the totality of morphological properties and features of the course of metabolic processes. In this case, the significance of one or another property of an object is endowed with meaning. The placement of a microorganism into one or another and the assignment of a name depend primarily on the type of cellular organization, the morphology of cells and colonies, as well as the nature of growth.
Taking into account functional characteristics provides for the possibility of microorganisms using various nutrients. Also important is the dependence on certain physical and chemical environmental factors, and in particular the path to energy production. There are microbes whose identification requires chemotaxonomic studies. Pathogenic microorganisms require serodiagnosis. A determinant is used to interpret the results of the above tests.
In molecular genetic classification, the structure of the molecules of the most important biopolymers is analyzed.
The procedure for identifying microorganisms
Nowadays, identification of a specific microscopic organism begins with isolating its pure culture and analyzing the 16S rRNA nucleotide sequence. Thus, the place of the microbe on the phylogenetic tree is determined, and subsequent specification by genus and species is carried out using traditional microbiological methods. A coincidence value of 90% allows us to determine the genus, and 97% - the species.
An even clearer differentiation of microorganisms by genus and species is possible when using polyphyletic (polyphasic) taxonomy, when the determination of nucleotide sequences is combined with the use of information at various levels, up to ecological. That is, a preliminary search is carried out for groups of similar strains, followed by determining the phylogenetic positions of these groups, recording the differences between the groups and their closest neighbors, and collecting data that allows the groups to be differentiated.
Main groups of eukaryotic microorganisms: algae
This domain includes three groups where there are microscopic organisms. We are talking about algae, protozoa and fungi.
Algae are unicellular, colonial or multicellular phototrophs that carry out oxygenic photosynthesis. The development of a molecular genetic classification of microorganisms belonging to this group has not yet been completed. Therefore, at the moment, in practice, the classification of algae is used based on the composition of pigments and reserve substances, the structure of the cell wall, the presence of mobility and the method of reproduction.
Typical representatives of this group are unicellular organisms belonging to dinoflagellates, diatoms, euglena and green algae. All algae are characterized by the formation of chlorophyll and various forms of carotenoids, but the ability to synthesize other forms of chlorophylls and phycobilins is manifested differently in representatives of the group.
The combination of certain pigments causes cells to be colored in different colors. They can be green, brown, red, golden. Cell pigmentation is a species characteristic.
Diatoms are single-celled planktonic forms that have the appearance of a silicon bivalve shell. Some representatives are capable of gliding movement. Reproduction is both asexual and sexual.
The habitats of single-celled organisms are freshwater bodies of water. They move using flagella. There is no cell wall. Capable of growing in darkness due to the oxidation of organic substances.
Dinoflagellates have a special cell wall structure; it consists of cellulose. These planktonic unicellular algae have two lateral flagella.
For microscopic representatives, habitats include fresh and sea water bodies, soil and the surface of various terrestrial objects. There are immobile species, and some are capable of locomotion using flagella. Like dinoflagellates, green microalgae have a cellulose cell wall. Characteristic storage of starch in cells. Reproduction is carried out both asexually and sexually.
Eukaryotic organisms: protozoa
The basic principles of classification of microorganisms belonging to protozoa are based on morphological characteristics, which vary greatly among representatives of this group.
They can lead a sedentary lifestyle or move with the help of various devices: flagella, cilia and pseudopods. Within the taxonomic group of protozoa there are several other groups.
Representatives of protozoa
Amoebas feed by endocytosis, move with the help of pseudopods, the essence of reproduction lies in primitive bisection. Most amoebas are free-living aquatic forms, but there are also those that cause diseases in humans and animals.
The cells of ciliates have two different nuclei; asexual reproduction involves transverse division. There are representatives that are characterized by sexual reproduction. A coordinated system of cilia takes part in the movement. Endocytosis is carried out by capturing food in a special oral cavity, and the remains are eliminated through an opening at the posterior end. In nature, ciliates live in bodies of water contaminated with organic matter, as well as in the rumen of ruminants.
Flagellates are characterized by the presence of flagella. Absorption of dissolved nutrients is carried out by the entire surface of the CPM. Division occurs only in the longitudinal direction. Among flagellates there are both free-living and symbiotic species. The main symbionts of humans and animals are trypanosomes (cause sleeping sickness), leishmania (cause difficult-to-heal ulcers), Giardia (lead to intestinal disorders).
Sporozoans have the most complex life cycle of all protozoans. The most famous representative of sporozoans is the malarial plasmodium.
Eukaryotic microorganisms: fungi
The classification of microorganisms classifies representatives of this group as heterotrophs. Most are characterized by the formation of mycelium. Respiration is usually aerobic. But there are also facultative anaerobes that can switch to alcoholic fermentation. Reproduction methods are vegetative, asexual and sexual. It is this sign that serves as a criterion for further
If we talk about the significance of the representatives of this group, then the combined non-taxonomic group of yeasts is of greatest interest here. This includes mushrooms that lack the mycelial stage of growth. Among yeasts there are many facultative anaerobes. However, pathogenic species also occur.
Main groups of prokaryotic microorganisms: archaea
The morphology and classification of prokaryotic microorganisms unites them into two domains: bacteria and archaea, the representatives of which have many significant differences. Archaea do not have the peptidoglycan (murein) cell walls typical of bacteria. They are characterized by the presence of another heteropolysaccharide - pseudomurein, which does not contain N-acetylmuramic acid.
Archaea are divided into three phyla.
Structural features of bacteria
The principles of classification of microorganisms that unite microbes into a given domain are based on the structural features of the cell membrane, and in particular the content of peptidoglycan in it. There are currently 23 phyla in the domain.
Bacteria are an important link in the cycle of substances in nature. The essence of their significance in this global process lies in the decomposition of plant and animal residues, the purification of water bodies polluted with organic matter, and the modification of inorganic compounds. Without them, the existence of life on Earth would become impossible. These microorganisms live everywhere; their habitat can be soil, water, air, the human body, animals and plants.
Based on the shape of the cells, the presence of devices for movement, and the articulation of cells among themselves in this domain, the subsequent classification of microorganisms is carried out within. Microbiology considers the following types of bacteria based on the shape of the cells: round, rod-shaped, filamentous, convoluted, spiral. According to the type of movement, bacteria can be immobile, flagellated, or move by secreting mucus. Based on the way cells articulate with each other, bacteria can be isolated, linked in the form of pairs, granules, and branching forms are also found.
Pathogenic microorganisms: classification
There are many pathogenic microorganisms among rod-shaped bacteria (pathogens of diphtheria, tuberculosis, typhoid fever, anthrax); protozoa (malarial plasmodium, toxoplasma, leishmania, lamblia, trichomonas, some pathogenic amoebas), actinomycetes, mycobacteria (causative agents of tuberculosis, leprosy), mold and yeast-like fungi (causative agents of mycoses, candidiasis). Fungi can cause all sorts of skin lesions, for example different types of lichen (with the exception of shingles, which is caused by a virus). Some yeasts, being permanent inhabitants of the skin, do not have a detrimental effect under conditions of normal functioning of the immune system. However, if the activity of the immune system decreases, they cause the appearance of seborrheic dermatitis.
Pathogenicity groups
The epidemiological danger of microorganisms is a criterion for grouping all pathogenic microbes into four groups corresponding to four risk categories. Thus, the pathogenicity groups of microorganisms, the classification of which is given below, are of the greatest interest to microbiologists, since they directly affect the life and health of the population.
The safest, pathogenicity group 4, includes microbes that do not pose a threat to the health of an individual (or the risk of this threat is negligible). That is, the risk of infection is very small.
Group 3 is characterized by a moderate risk of infection for an individual and a low risk for society as a whole. Such pathogens can theoretically cause disease, and even if this happens, there are proven effective treatments, as well as a set of preventive measures that can prevent the spread of infection.
The 2nd group of pathogenicity includes microorganisms that pose a high risk for the individual, but low for society as a whole. In this case, the pathogen can cause severe illness in humans, but it does not spread from one infected person to another. Effective methods of treatment and prevention are available.
The 1st group of pathogenicity is characterized by a high risk for both the individual and society as a whole. A pathogen that causes severe disease in humans or animals can be easily transmitted in a variety of ways. Effective treatments and preventative measures are usually lacking.
Pathogenic microorganisms, the classification of which determines their belonging to one or another pathogenicity group, cause great damage to public health only if they belong to the 1st or 2nd group.
Currently, all microorganisms are divided into three kingdoms:
- 1. Prokaryotes are nuclear-free cells, the nuclear components are not separated from the cytoplasm by a membrane. These include bacteria and blue-green algae.
- 2. Eukaryotes are nuclear organisms; the nuclear membrane delimits DNA from the cytoplasm. These include microscopic algae, microscopic fungi (molds and yeasts).
- 3. The kingdom of viruses. These include pathogens of infectious diseases and bacteriophages (bacterial viruses).
Taxonomy(toxonomy) is a science dealing with the classification, nomenclature and identification of microorganisms.
Under classification microorganisms understand their distribution into groups (taxa) based on common characteristics. Each group has its own name: kingdoms - regnum, department - divisio, section - section, class - ciassis, order - ordo, family - familia, genus - genus, species - species. Most the small unit of classification is the species- a group of microorganisms endowed with common stable characteristics and descending from a common ancestor.
The species is divided into subspecies or variants. Subspecies, in turn, can also be subdivided on the basis of differences in any characteristic - antigenic - serovar, biochemical - biovar, relationship to phages - phagovar, pathogenicity - pathovar.
In microbiology the terms are used “species”, “strain”, “clone”, “culture”.
View- this is a collection of individuals that have a common origin and genotype, morphological, physiological and other characteristics that can, under certain conditions, cause the same processes.
Culture- these are microorganisms isolated from animals, humans, plants, etc. and grown on nutrient media. Microbial cultures can be pure (from one type of microorganism) or mixed (from several types)
Strain- a culture of the same type, but isolated from different objects and therefore characterized by a slight change in properties.
Clone- a culture of microorganisms grown from one microbial cell on an artificial nutrient medium. All offspring have exactly the same properties.
In order to classify a microorganism into any group, it is necessary to determine its main characteristics: morphology, motility, Gram staining, the presence of a capsule and the ability to form an endospore, cultural and biochemical properties and some other characteristics.
Identification- assignment of microorganisms to a specific taxon (species) based on specific characteristics.
Nomenclature- a system of names used in a certain field of knowledge.
Bacteria are named in accordance with the rules of the International Code of Nomenclature of Bacteria introduced on January 1, 1980. The dual nomenclature proposed back in the 18th century was adopted. K. Linnaeus. The name of the bacteria is given in Latin and consists of two words. The first word denotes the genus to which the bacterium belongs, the second is the name of the species. The generic name is written with a capital letter, the specific name with a lowercase letter.
Currently, the classification of microorganisms is based on a set of the following characteristics:
- 1. Phenotypic signs- external signs. Not related to heredity and genotype. Phenotypic characteristics determine the place of microbes in the classification according to their similarity in morphological characteristics, cultural, physiological, tinctorial, etc. For example, according to Krasilnikov’s classification, microorganisms are divided into three groups (based on appearance):
- 1 - spherical (5 types)
- 2 - rod-shaped
- 3 - crimped
- 2. genotypic traits. Gene systematics is based on the study of the nucleotide composition of DNA and the most important characteristics of the genome (size, volume, molecular weight, etc.). Genetic relatedness between bacteria is determined by the degree of DNA homology. The more identical genes, the higher the degree of DNA homology and the closer the genetic relationship. Those. genotypic characteristics determine the place of microbes in the classification by kinship (origin).
There is a second approach to the taxonomy of bacteria, which has practical goals, i.e. serves to identify bacteria - to establish belonging to a specific species. For this purpose, determinants have been created that are used to determine the type of a particular microorganism.
International determinants of bacteria include “Identifier of Bacteria 9”, published in 1993. 35 groups of genera have been identified within 4 divisions of prokaryotes. The divisions are classified according to the presence of a cell wall (peptidoglycan).
- 1. Gracilicutes (or thin-skinned) - gram-negative bacteria
- 2. Firmicutes (or thyme) - gram-positive bacteria
- 3. Tenericutes (or tender-skinned) - organisms that do not have a cell wall. Mycoplasmas.
- 4. Mendosicutes are bacteria, most of which, although they have a cell wall, do not contain peptidoglycan. Some are gram positive. Others are gram-negative - this includes archaebacteria.
The tasks of taxonomy are to show the degree of relationship between organisms and the evolutionary relationship. The principles of classification are studied by taxonomy (from the Greek taxis - arrangement, homos - law). The main taxonomic units in the taxonomy of microorganisms are as follows:
Kingdom based on the type of cellular organization (prokaryotes, eukaryotes, viruses)
Department - bacteria
Class
Order
Family
Species - bacteria are a collection of microorganisms of the same genotype that, under the same conditions, have the same phenotypic characteristics. For example: Salmonella typhi (genus, species). Within one species, individual characters. Individual properties can vary, therefore, within a species, species can be defined under species (morphological variants, biovariants, chemovariants, phagovars, serovars (differing in antigenic properties)).
Establishing genus and species is called bacterial identification. For identification, it is necessary to study all the properties of microorganisms and discover these properties in the microbial world. Identification of a microorganism occurs according to a set of the following properties: tinctorial, cultural, biochemical, pathogenicity factors, antigenic properties and relation to phages. To facilitate identification, special identification keys have been proposed for certain groups of microorganisms; these are sets of characteristics for a microorganism - family, genus and species. Only pure cultures of the organism are identified.
^ CHKM– microbes of one type grown in laboratory conditions on artificial nutrient media.
Strain– a pure culture isolated from a specific source, or a pure culture isolated from one source, but at different times.
^ Clone– a pure culture of microbes obtained from a single bacterial cell
Microbial population- a collection of individuals of one species that exist for a long time in a certain territory and are isolated from other individuals of the same species, a population is a unit of evolution. For example, the population of Salmonella typhi in the northern regions differs from those living in the southern regions.
^ Genetic taxonomy
Identification of bacteria based on genetic relatedness. It is based on the determination of the genetic structures of the cell - DNA, extrachromosomal structures - plasmids, transpasons. It has been proven that the composition of DNA bases is species-specific, i.e. the percentage of GC is determined from the total content of all bases; this may be important for determining the type. The similarity or complementarity of acids between different organisms is determined by hybridization. The homology of the nucleic acid sequence is determined. This method determines the relationship between microorganisms. The % similarity of one order is 80%, for a family it is 90%, for a genus it is 95%, for a species it is almost 100%.
The first work in which bacteria were described and classified was compiled by Bergey in 1923. In it, bacteria are divided into 25 groups. There are only 20 pathogenic groups. In the key, bacteria are divided into Gracilicutes - thin-walled, Firmicutes - thick-walled, Teniricutes - soft-bodied.
^ Ultrastructure of a bacterial cell
A bacterial cell has permanent structures - cell wall, cytoplasmic membrane, cytoplasm, ribosomes, nucleoid. Non-permanent - flagella, villi, capsule, inclusions, spores.
^ Permanent structures.
Cell wall: Functions – protective, shape-forming, participates in division, transport, receptor, determines the antigenic properties of the bacterium, determines the tinctorial properties of the bacterium (paint diffusion). Violation of cell wall synthesis leads either to the death of the bacterium, or to the formation of spheroblasts, protoblasts (lose the ability to reproduce) or L-form (retained the reproductive function). Loss is associated with antibiotics, the effect of lysocine. The loss will be accompanied by (a) process and cannot be treated with antibiotics.
The main element of CS Murein is a polymer, the fragments are linked by unique amino acids (only found in prokaryotes), murein is a target for antibiotics, and it is the selectivity of antibiotics that is associated with murein. KlS G(-) is thin, it contains a rigid layer formed by peptidoglycan (20%) and a plastic layer, its thickness is significant and it contains a lot of lipopolysaccharide (80%), which has a basic part - a polysaccharide molecule, lipid-A (responsible for toxicity, pyrogenicity), O-specific side fragments (consist of polysaccharides, determine antigenic properties). The thicker G(+) wall consists of multilayer peptidoglycan 90%, teichoic acids. Tk penetrate the cell wall and bind to PGs, due to which antigenic properties are determined; there are almost no lipopolysaccharides. Porin proteins penetrate the CS of bacteria, but the sizes are different: G(-) is larger, G(+) is smaller.
^ Cytoplasmic membrane: function: selective permeability, osmotic barrier, participation in metabolism, energy metabolism (contains many enzymes - cytochromes, oxidases, dehydrogenases, atephases), replication, participation in sporulation, excretory.
Cytoplasm The colloidal system consists of water inclusions of organelles, the place where metabolism takes place.
Nucleoid closed DNA (bacterial chromosome) has a haploid set. Methods for identifying nucleoids: special microchemical reaction according to Felgin, detection using an electron microscope. Functions: storage of genetic information, determination of cell viability.
^ Non-permanent structures.
Capsule: according to the chemical composition, polysaccharide substance, mucous layer, proteins, lipids. Can be large (larger than a cell), small can be detected. Functions: protective (from phagocytosis by macrophages), an additional factor of pathogenicity, protects against the action of antilels, antibiotics, imparts adhesive properties. Capsule products exclusively in a living organism, and not in the external environment, on an artificial nutrient medium (enriched with polysaccharides), a small part of microbes can produce a capsule (pneumococci, clepsiella, the causative agent of anthrax).
Controversy: is a protective reaction inherent in some microorganisms when exposed to unfavorable conditions (external environment - lack of water, nutrients, aging culture, unfavorable temperature), usually rod-shaped (depending on this they are divided into bacilli, clastridia (Sp +) and other bacteria ). Sporulation in prokaryotes is a form of preservation of the genetic material of the cell under unfavorable conditions, and not a method of reproduction (from one cell to 1 spore). A prerequisite for sporulation is the presence of oxygen. They can live in the external environment for decades. After germination (4-5 hours) vegetative form (capable of division, metabolism). The spore shells are destroyed, a growth tube is formed, and the cell wall is synthesized.
Sporulation process:
1. formation of a spore-bearing zone in which the nucleoid is located,
2. formation of prospores, in which the sporogenic zone is separated,
3. formation of the cortex - spore shell,
4. death of the vegetative part of the cell and release of the spore.
By localization: the spore can occupy a central, subterminal, or terminal position.
In size: less than the diameter of the rod (bacillus), greater than the diameter of the rod (clostridium)
Spore property:
Sustainability. Thermo-related to the chemical composition: little water 5-10%, a lot of calcium salts, dipiolic acid, so it can withstand pasteurization and boiling. To kill a spore you need T=180-200 0, 20 minutes, t=120 0 + 1.5 atm.
Sporulation is inherent:
Bacillus anthracide - anthrax
Clastridia – gangrene, tetanus
Causative agents of botulism
Flagella: organs of movement. Surface structures in the form of filaments, visible only in an electron microscope, contain the contractile protein flagellin and are attached to the cytoplasmic membrane. According to the number and location, everything is divided into: monotrichia, lophotrichia (bundle), amphotrichia (two bundles), peritrichia (along the perimeter), Length is greater than the length of the cell. The most mobile are monotrichia and lophotrichia.
Methods for studying mobility:
hanging drop
Crushed drop
Dark-field microscopy
Phase contrast microscopy
Villi: thin hollow filaments of a protein nature, short, that cover the surface of the cell, a lot, do not perform locomotor functions. Functions: adhesion (type 1 villi, the pathogenicity of the bacterium is associated with them), conjugative (genital villi), there are few of them.
Inclusions: volutin grains (metaphosphate grains have the property of methochromasia - the ability to be colored differently from the color of the dye), fatty grains, glycogen. Nutrient reserve.
ABOUT
^
BASIC MORPHOLOGICAL FORMS OF BACTERIA.
Globular
Rod-shaped
Convoluted (vibrios, spirilla (have lophotrichia), spirochetes)
Spirochetes
Ricketia
Actinomycetes
Chlamydia
Mycoplasmas
Spirochetes: thread-like, spirally twisted, convoluted there is a locomotor internal apparatus represented by an axial thread of myofibrils.
WITH 
spirochete family.
Borel - rough curls
Treponemas - uniform curls
Leptospira have primary whorls and secondary, thickened ends
Movement Types:
Helical (treponema, leptospira)
Forward-backward, right-left
Smooth
Sharp
Rickettsia: prokaryotes, small in size,
Polymorphic (cocoid, cocobacteriol, rod-shaped, long filamentous) is associated with the characteristics of division, the septum is incomplete and therefore the cells can take on different shapes.
Ecological niche: inhabit the body of arthropods, transmitted transmissively (bites) from insects - lice, fleas, ticks. Examples: typhus.
Detection methods: staining - Romanovsky - Ginza, according to Zdorovsky, while the cells in which the rickettsia are located are stained in one color, the nucleus in another, the rickettsia itself in a third. Microscopy: color, phase-contrast, electronic.
Morphological forms:
Extracellular - an elementary body, spherical in shape, small in size 0.3 microns, having a cell wall, membrane
Intracellular – reticular body, is at different stages of maturation, can only be found inside the cell, where it matures and breaks the cell.
Mycoplasmas: diseases: pneumonia, bronchitis, urogenital mycoplasmosis, neonatal pathology.
Actinomycetes: prokaryotes similar to fungi. Polymorphic (branched, short rods) are capable of forming mycelium, Gram +, acid-labile. They grow slowly. Habitat: external environment, oral cavity (normal microflora). They can reproduce by spores.
Study: staining - according to Romanovsky-Ginza, cultivation.