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theme: Systematics, nomenclature of microorganism, principles of classification of microorganisms.

The tasks of systematics are to show the degree of relationship between organisms and the evolutionary relationship. It studies the principles of classification - taxonomy (from the Greek. taxis-location, homos - law) The main taxonomic units in the systematics of microorganisms are as follows:

• 
  Kingdom based type of cellular organization (prokaryotes, eukaryotes, viruses)
• 
  Department - bacteria
• 
  Class
• 
  Order
• 
  Family

The basic taxonomic unit in microbiology is a species, genus, family.

A species is a group of microorganisms of the same genotype that, under the same conditions, have the same phenotypic characteristics. For example: Salmonella typhi (genus, species). Within the same species, individual characters. Individual properties may vary, therefore, within a species, subspecies may be determined (morphological variants, biovariants, chemovariants, fagovars, serovars (differ in antigenic properties)).

Establishing belonging to the genus and species is called the identification of bacteria. For identification, it is necessary to study all the properties of microorganisms, to discover these properties in the world of the microbe. A microorganism is identified by a set of the following properties: tinctorial, cultural, biochemical, pathogenicity factors, antigenic properties, and relation to phages. To facilitate identification, special identification keys for certain groups of microorganisms are proposed, these are sets of features for a microorganism - family, genus and species. Only pure cultures of the organism are subjected to identification.

^ ChKM- microbes of the same species grown in laboratory conditions on artificial nutrient media.

Strain- a pure culture isolated from a specific source, or a pure culture isolated from the same source, but at different times.

^ Clone- a pure culture of microbes obtained from a single bacterial cell

microbial population- a set of individuals of one species for a long time existing in a certain territory and isolated from others of the same species, the 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 relationship. 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 vitospecific, i.e. the percentage of HC from the total content of all bases is determined; this may have a value of e for the definition of the species. The similarity or complementarity of acids between different organisms is determined by the method of hybridization. Determine the homology of the nucleic acid sequence. This method determines the relationship between microorganisms. The % similarity of one order is 80%, for the family 90%, the genus 95% for the species almost 100%.

The first work in which bacteria were described and classified was compiled by Burgey in 1923. In it, bacteria are divided into 25 groups. Pathogenic in total 20 groups. In the determinant, 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, shaping, participates in division, transport, receptor, determines the antigenic properties of the bacterium, determines the tinctorial properties of the bacterium (diffusion of paint). Violation of the synthesis of the cell wall 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 function of reproduction). The loss is associated with antibiotics, the influence of lysocine. The loss will be followed by () the process and antibiotics are not treated.

The main element c.S. Murein is a polymer, the fragments are bound by unique amino acids (only in prokaryotes), murein is a target for antibiotics, it is the selectivity of antibiotics that is associated with murein. G(-) CL is thin, a rigid layer formed by peptidoglycan (20%) is isolated in it and its plastic layer is significant and contains a lot of lipopolysaccharide (80%), which has a basic part, this is a polysaccharide molecule, lipid-A (responsible for toxicity, pyrogenicity), O-specific side fragments (consist of polysaccharides, determine antigenic properties). The G(+) thicker wall consists of 90% multilayer peptidoglycan, teichoic acid. Tcs penetrate the cell wall and bind to PGs, due to them antigenic properties are determined, there are almost no lipopolysaccharides. Porin proteins penetrate the bacterial CM, but the sizes are different for G(-) larger, for G(+) 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. Nucleoid detection methods: a special microchemical reaction according to Felgin, detection in an electron microscope. Functions: storage of genetic information, determination of cell viability.

^ non-permanent structures.

Capsule: according to the chemical composition, polysaccharide content, mucous layer, proteins, lipids. It can be large (larger than a cage), small can be found. Functions: protective (against phagocytosis by macrophages), an additional factor of pathogenicity, protects against the action of antilels, antibiotics, imparts adhesive properties. Capsule production only in a living organism, and not in the external environment, on an artificial nutrient medium (enriched with polysaccharides), a small part of the microbes can produce a capsule (pneumococci, clepsiel, anthrax).

controversy: is a protective reaction inherent in some microorganisms, when exposed to adverse conditions (external environment - lack of water, nutrients, aging of the 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 adverse conditions, and not a method of reproduction (from one cell to 1 spore). The prerequisite for spore formation is the presence of oxygen. In the external environment, they can live for decades. After germination (4-5 hours) vegetative form (capable of division, metabolism). The spore shells are destroyed, a growth tube is formed, the synthesis of the cell wall.

The sporulation process:

1. the formation of a spore-bearing zone in which the nucleoid is located,

2. the formation of a prospore, while the sporogenous zone is separated,

3. formation of a cortex - a spore shell,

4. death of the vegetative part of the cell and release of the spore.

By localization: the dispute can occupy a central position, subterminal, terminal.

In size: less than the diameter of the rod (bacillus), more than the diameter of the rod (clostridia)

Spore property:

Sustainability. Thermally related to the chemical composition: little water 5-10%, a lot of calcium salts, there is dipiolinic acid, therefore it withstands pasteurization, boiling. To kill the spore, T=180-200 0 , 20 min, t=120 0 + 1.5 atm.

Sporulation is inherent:

Bacille anthracid - anthrax

Clastridia - gangrene, tetanus

causative agents of botulism

Flagella: organs of movement. Surface structures in the form of threads are found only in an electron microscope as part of the contractile protein flagellin and are attached to the cytoplasmic membrane. According to the number and location, they are all divided into: monotrichia, lophotrichia (bundle), amphotrichia (two beams), peritrichia (along the perimeter), The length of W is greater than the length of the cell. The most mobile are monotrichia, lophotrichia.

Methods for studying mobility:

hanging drop

crushed drop

Dark field microscopy

Phase contrast microscopia

Villi: thin hollow filaments of protein nature, short, which cover the surface of the cell, a lot, do not perform a locomotor function. Functions: adhesion (type 1 villi, the pathogenicity of bacteria is associated with them), conjugative (genital villi) there are few of them.

Inclusions: volutin grains (metaphosphate have the property of methochromasia - the ability to stain not in the color of the dye), fat grains, glycogen. Nutrient supply.

O

^ MAIN MORPHOLOGICAL FORMS OF BACTERIA.

• 
  spherical
• 
  rod-shaped
• 
  Convoluted (vibrios, spirilla (have lophotrichia), spirochetes)

Prokaryotes with specific morphology:

• 
  Spirochetes
• 
  Riquetsia
• 
  actinomycetes
• 
  Chlamydia
• 
  Mycoplasmas

Spirochetes: filiform, spirally twisted, tortuous; there is a locomotor internal apparatus represented by an axial thread of myofibrils.

FROM

families of spirochetes.

1. 
   Borel - coarse curls
2. 
   Treponema - uniform curls
3. 
   Leptospira have primary whorls, and secondary, thickened ends.

Differentiation takes place: by the number of curls, the nature of the ends, the nature of the movement.

Movement types:

• 
  Helical (treponema, leptospira)
• 
  Forward-backward, right-left

The nature of the movement:

• 
  Smooth
• 
  Sharp

Study methods: staining according to Romanovsky-Ginza. Borelia are blue, the rest are pink. Microscopy dark-field microscopy, phase-contrast.

Rickettsia: prokaryotes, small sizes,

Polymorphic (coco-shaped, cocobacteriol, rod-shaped, long filamentous) is associated with the characteristics of division, the septum is incomplete and therefore the cells can take on a different shape.

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 the third. Microscopy: color, phase-contrast, electronic.

Morphological forms:

• 
  Extracellular - elementary body, spherical shape, small size 0.3 microns, having a cell wall, a membrane
• 
  Intracellular - a reticular body, is at different stages of maturation, can only be found inside the cell, where it matures and breaks the cell.

Detection methods: staining according to Romanovsky - Ginza, phase-contrast microscopy, immunofluorescence reaction, enzyme immunoassay method.

Mycoplasmas: diseases: pneumonia, bronchitis, urogenital mycoplasmosis, neonatal pathology.

actinomycetes: prokaryotes resembling fungi. Polymorphic (branched, short sticks) are able to form mycelium, Gram +, acid-resistant. Grow slowly. Habitat: external environment, oral cavity (normal microflora). They can reproduce by spores.

Study: staining according to Romanovsky-Ginza, cultivation.

Microorganisms are 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 systematics, microorganisms belong to three kingdoms:

Vira- they include viruses;

Eucariotae- these include protozoa and fungi;

Procariotae- these include true bacteria, rickettsia, chlamydia, mycoplasmas, spirochetes, actinomycetes.

The main differences between prokaryotes and eukaryotes are that prokaryotes do not have:

a morphologically formed nucleus (there is no nuclear membrane and there is no nucleolus), its equivalent is the nucleoid, or genophore, which is a 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;

mesh apparatus of Golgi;

endoplasmic reticulum;

mitochondria.

There are also a number of features or organelles common to many, but not all, prokaryotes that distinguish them from eukaryotes:

numerous invaginations of the cytoplasmic membrane, which are called mesosomes, they are associated with the nucleoid and are involved in cell division, sporulation, and respiration of the bacterial cell;

specific cell wall component- murein, according to the chemical structure - it is peptidoglycan (diaminopiemic acid);

plasmids- autonomously replicating ring-shaped molecules of double-stranded DNA with a molecular weight less than the chromosome of bacteria. They are located along with the nucleoid in the cytoplasm, although they can be integrated into it, and carry hereditary information that is not vital for the microbial cell, but provides it with certain selective advantages in the environment. The most famous plasmids are:

1. (F-plasmids), providing conjugative transfer between bacteria;

   (R-plasmids)- drug resistance plasmids that ensure circulation among bacteria of genes that determine resistance to chemotherapeutic agents used to treat various diseases.

As well as for plants and animals, binary nomenclature is used for the name of microorganisms, that is, a generic and specific name, but if the researchers cannot determine the species and only the belonging to the genus is determined, then the term "species" is used. Most often this takes place when identifying microorganisms with non-traditional nutritional needs or living conditions.

The genus name is usually either based on the morphological character of the corresponding microorganism (e.g. Staphylococcus, Vibrio, Mycobacterium) or derived from the name of the author who discovered or studied the pathogen (e.g. Neisseria, Shigella, Escherichia, Rickettsia, Gardnerella).

The specific 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 - Escherichia coli).

In addition, in the 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.).

The kingdom of prokaryotes includes the department of cyanobacteria and the department of eubacteria, which, in turn, is divided into orders:

actually bacteria (departments Gracilicutes, Firmicutes, Tenericutes, Mendosicutes);

actinomycetes;

spirochetes;

rickettsia;

chlamydia.

bacteria- These are prokaryotic, predominantly unicellular microorganisms that can also form associations (groups) of similar cells, characterized by cellular, but not organismal similarities.

Orders are divided into groups. The main taxonomic criteria for classifying bacterial strains into one group or another are:

morphology of microbial cells (cocci, rods, convoluted);

relation to Gram stain- tinctorial properties (gram-positive and gram-negative);

type of biological oxidation- aerobes, facultative anaerobes, obligate anaerobes;

ability to spore.

Further differentiation of groups into families, genera and species, which are the main taxonomic category, is carried out on the basis of the study of biochemical properties. This principle is the basis for the classification of bacteria given in special manuals - determinants of bacteria.

A species is an evolutionarily established set of individuals with a single genotype, which under standard conditions is manifested by similar morphological, physiological, biochemical features. For pathogenic bacteria, the definition of "species" is supplemented by the ability to cause certain nosological forms of diseases.

There is an intraspecific differentiation of bacteria into variants:

by biological properties (biovars or biotypes);

on biochemical activity (enzyme products);

by antigenic structure (serovars or serotypes);

by sensitivity to bacteriophages (fagovars or phage types);

on resistance to antibiotics (resistant products).

In microbiology, special terms are widely used - culture, strain, clone.

culture is a collection of bacteria visible to the eye on nutrient media. Cultures can be pure (a collection of bacteria of one species) and mixed (a collection of bacteria of two or more species).

Strain is a collection of bacteria of the same species isolated 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 is a collection of bacteria that are the offspring of a single cell.

Systematics and nomenclature of microorganisms.

INTRODUCTION TO MICROBIOLOGY

Lesson 1-2 The main characteristics of microbes. Purpose and tasks of microbiology. Systematics and nomenclature of microorganisms. Classification and morphology of bacteria. Structure and classification: fungi, protozoa, viruses. Methods for studying the morphology of microbes. Subject and tasks of microbiology. Basic properties of microorganisms.

The main characteristics of microbes. Purpose and tasks of microbiology.

Microbiology (from the Greek "mikros" - small, "bios" - life, "logos" - teaching) is a science that studies the world of the smallest living beings - microorganisms and the processes caused by microorganisms.

Microbiology studies the morphology of microorganisms, the patterns of their development and the processes that they cause in the environment, as well as their role in nature and human economic activity.

The world of microorganisms includes bacteria, yeast, microscopic (mold) fungi.

Microbiology studies the structure, life activity, living conditions and development of the smallest organisms, called microbes, or microorganisms.

“Invisible, they constantly accompany a person, invading his life either as friends or as enemies,” said Academician V. L. Omelyansky. Indeed, microbes are everywhere: in the air, in water and in soil, in the human body and animals. They can be useful and are used in the manufacture of many foods. They can be harmful, cause people to get sick, spoil food, etc.

Microbes were discovered by the Dutchman A. Leeuwenhoek (1632-1723) at the end of the 17th century, when he made the first lenses that gave an increase of 200 times or more. The microcosm he saw struck him; Leeuwenhoek described and sketched the microorganisms he had found on various objects. He laid the foundation for the descriptive nature of the new science. The discoveries of Louis Pasteur (1822-1895) proved that microorganisms differ not only in form and structure, but also in their vital activity. Pasteur found that yeasts cause alcoholic fermentation, and some microbes are capable of causing contagious diseases in humans and animals. Pasteur went down in history as the inventor of the method of vaccination against rabies and anthrax. The contribution to microbiology of R. Koch (1843-1910) is world famous - he discovered the causative agents of tuberculosis and cholera, I. I. Mechnikov (1845-1916) - developed the phagocytic theory of immunity, the founder of virology D. I. Ivanovsky (1864-1920), N F. Gamaleya (1859-1940) and many other scientists.

Systematics and nomenclature of microorganisms.

The world of microorganisms is diverse and the organisms in it differ in the level of organization of genomes, the presence and composition of protein-synthesizing systems and the cell wall. In accordance with these features, microorganisms are divided into 3 kingdoms: eukaryotes, prokaryotes, viruses.

Microorganisms- these are representatives of all kingdoms invisible to the naked eye (bacteria, fungi, protozoa, blue-green algae, viruses). They occupy the lower stages of evolution, but play an important role in the existence and development of nature, in the circulation of substances, in the pathology of humans, animals and plants.

eukaryotes have a differentiated nucleus, delimited from the cytoplasm by a nuclear membrane, a mitotic apparatus and a nucleolus. Eukaryotes include protozoa, yeasts, and filamentous fungi.

The nuclear DNA of eukaryotes is complexed with histones in a ratio of 1:1, the chromosomes are built in the form of nucleosomes, consisting of protein globules, and a DNA fragment of 200 base pairs in size. Eukaryotes have 80S ribosomes, mitochondria or chloroplasts, do not contain peptidoglycan, and are aerobic.

prokaryotes- these are organisms that do not have a formalized nucleus, but have an equivalent of the nucleus - a nucleoid, which is represented by one or more chromosomes located in the cytoplasm and not separated from it by any membrane. Prokaryotes do not have a differentiated mitotic apparatus; they do not have a nucleolus. They have 70S ribosomes, a cell wall containing peptidoglycan. The sizes of prokaryotes range from 1 to 20 microns, they do not have mitochondria and chloroplasts. Among prokaryotes there are aerobic and anaerobic organisms.

Systematics of microorganisms is engaged in a detailed description of the species of organisms, determining the degree of relationship between them, combining them according to the level of relationship into classification units - taxa. From here taxonomy is the science of the principles and methods of the distribution of organisms in a hierarchical plan.

Classification- an integral part of taxonomy, it distributes microorganisms into various taxa. The basic taxonomic unit is view.

View – This is an evolutionarily established set of microorganisms that have a common origin, a similar genotype, habitat and properties, as well as the ability to cause similar processes in the human body or the external environment.

Subsequent larger taxonomic units: genus, family, order, class, department, kingdom.

Currently, microbiology uses several main methods for classification.

1. Numerical approach. It is based on an assessment of the degree of similarity and difference of organisms according to the maximum possible number of phenotypic properties and manifestations. Sometimes more than 100 indicators are evaluated. To increase the reliability of the determination, the characteristics are assigned coefficients (they are also called weights). The more important this trait is for determining the pathogen, the less common it is in other microorganisms, the higher the weight of the trait and the more specific it determines this pathogen (for example, the production of plasmacoagulase in Staphylococcus aureus).

2. Genetic approach. It is based on the similarity in the DNA structure of the genomes of the studied bacteria. It is believed that microorganisms belonging to species 1 have 70 to 100% DNA homology. With a 60% coincidence, we can talk about bacteria belonging to the 1st genus. For genetic classification, the method of hybridization of nucleic acids is used, the percentage of guanine and cytosine in the DNA of the genome is studied, the molecular weight of DNA, the presence of plasmids are determined. Recently, especially for the intraspecific differentiation of microorganisms, the polymerase chain reaction method has been used.

3. Ribosomal RNA typing (ribotyping). It turned out that the ribosomal RNA of bacteria contains highly conserved sequences that changed insignificantly during evolution. Differences in the structure of ribosomal RNA make it possible to differentiate large taxa (orders, classes, families) in bacteria. The genetic mechanisms underlying the variability of microorganisms provide only the relative stability of traits that can vary within the same species. This gave rise to the concept of variants (types) of microorganisms that differ in individual features from standard species. So, they distinguish: morphological ( morphovars), biological ( biovars), enzymatic ( fermenters), different in resistance to antibiotics ( resistenswars) and bacteriophages ( fagovars) variants of bacteria. Along with this, individual species may include variants that differ in antigenic structure ( serovars), ecological niches in which they live ( ecoware) and pathogenicity for certain hosts ( patovars).

A strain is a culture of one type of microorganisms isolated from various sources (human, animal, environmental) or from the same source, but at different times. Typically, strains are designated by protocol numbers or named either by the source of isolation (aqueous, intestinal) or by the area where it was isolated. Strains of microbes of the same species can be completely identical or differ in the degree of virulence, metabolic activity, sensitivity to antibiotics and antiseptics, but the properties of individual strains do not go beyond the limits of this type of microorganism.

According to binomial nomenclature, each microorganism has a name consisting of two words: the first word means genus and is written with a capital letter, the second word means species and is written with a lowercase letter, for example Escherichia coli. It is possible to reduce the gender to the first letter, less common are reductions to the first two or three letters. Quite often, only the generic name is used, meaning all species of a given genus, or the fact that identification was carried out only to the genus. In this case, instead of the specific name, the abbreviation is used: spp.

Clone- a culture of microorganisms obtained from a single individual.

pure culture is microbial specimens of the same species grown on a nutrient medium.

The characteristics of microorganisms have determined a set of features and properties that are used in taxonomy and classification:

1. Morphological- size, shape, relative position.

2. Tinctorial- the ability to be stained with various dyes with complex staining methods. One of the most important traits is the relationship to Gram stain, which depends on the structure and chemistry of the cell wall. On this basis, all bacteria are divided into gram-positive and gram-negative.

3.cultural properties– features of bacterial growth on liquid and solid nutrient media.

4. Mobility bacteria. Distinguish between motile and non-motile bacteria. Motile bacteria are divided into crawling and floating, in which motility is associated with the presence of flagella.

5. Physiological properties- how to eat and breathe.

6. Biochemical properties- the ability to break down proteins, carbohydrates, fats to end products of metabolism.

7. Sensitivity to specific bacteriophages.

8. Antigenic properties(revealed in immunological reactions).

9. Lipid, protein and carbohydrate composition. Protein spectra are determined using the method of two-dimensional polyacrylamide gel electrophoresis, where mixtures of ribosomal, membrane and intracellular proteins are separated, obtaining protein spectra of the corresponding fraction of a certain bacterial species. The study of the composition of fatty acids is carried out using gas chromatography.

10.genetic properties. They are studied using methods gene systematics. The most accurate method for establishing genetic relationship is to determine the degree of DNA similarity.

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1. Fundamentals of microbiology

Microbiology as an independent science , which has its own objects and methods of research, was formed in the second half of the 19th century thanks to the works PasteurKoch, Erlich, Mechnikov, Ru and others, but also at the present time, as well as those closely related to it, biotechnology and Genetic Engineering is constantly and intensively developing.

Born as the science ofpathogens , i.e. as a branch of medicine, to date depending on the tasks to be solveddivided by :

industrial;

agricultural;

veterinary;

· sanitary;

medical microbiology.

Subject study medical microbiology are microorganisms — representatives of the normal microflora of the human body and pathogens of various human diseases, as well as methods of laboratory diagnostics, specific prevention and etiotropic therapy the diseases they cause.

2. Classification (systematics) of microorganisms

Microorganisms — this is 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- they include viruses;

· Eucariotae- these include protozoa and fungi;

· Procariotae- these include true bacteria, rickettsia, chlamydia,

mycoplasmas, spirochetes, actinomycetes.

Main differences prokaryotes from eukaryote are that prokaryotes do not have :

morphologically arranged nuclei(No nuclear membrane and missing nucleolus), its equivalent is nucleoid, or genefor 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 features or organelle, 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 bound to the nucleoid and involved in cell division, spore formation, and bacterial cell respiration;

specific cell wall component— murein , according to the chemical structure is peptidoglycan(diaminopiemic acid);

· plasmids — autonomously replicating circular double-stranded DNA molecules with a smaller molecular weight than the 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 one or the other selective advantages in the environment. Most famous plasmids :

- (F-plasmids), providing conjugation transfer between bacteria;

- (R-plasmids)- drug resistance plasmids that ensure circulation among bacteria of genes that determine resistance to chemotherapeutic agents used to treat various diseases.

As well as for plants and animals, the name of microorganisms is used binary nomenclature , - that is generic and specific name, but if the researchers cannot determine the species affiliation and only the belonging to the genus is determined, then the term "species" is used. Most often this takes place when identifying microorganisms with non-traditional nutritional needs or living conditions.

Name kind usually either based on the morphological trait of the corresponding microorganism (eg, Staphylococcus, Vibrio, Mycobacterium) or are derived from the name of the author who discovered or studied this pathogen (eg, 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 - Escherichia coli).

In addition, in the 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 proper (Departments Gracilicutes, Firmicutes, Tenericutes, Mendosicutes);

actinomycetes;

· spirochetes;

rickettsia;

chlamydia.

bacteria - this is prokaryotic, mainly unicellular microorganisms, which may same form associations(groups) similar cells, characterized cellular but not organismic similarities.

Orders subdivided into groups. The main taxonomic criteria , which make it possible to classify bacterial strains as one or another group, are :

morphology of microbial cells (cocci, rods, convoluted);

relation to Gram stain - tinctorial properties (gram-positive and gram-negative);

type of biological oxidation - aerobes, facultative anaerobes, obligate anaerobes;

ability to spore formation.

Further group differentiation on families, genera and species, that are main taxonomic category, is carried out on the basis of study of biochemical properties in. This principle is the basis classification of bacteria given in special guidelines — determinants of bacteria .

View is an evolutionarily established set of individuals with a single genotype, which under standard conditions manifested by similar morphological, physiological, biochemical features. For pathogenic bacteria the definition of "type" is supplemented by the ability to cause certain nosological forms of diseases. There is an intraspecific differentiation of bacteria into variants:

By biological properties (biovars or biotypes);

By biochemical activity (enzyme products);

By antigenic structure (serovars or serotypes);

By sensitivity to bacteriophages (fagovars or phage types);

resistance to antibiotics (resistance products).

In microbiology, special terms are widely used - culture, strain, clone.

culture - this is visible to the eye collection of bacteria on nutrient media. cultures can be clean () and mixed (collection of two or more species of bacteria).

Strain - this is a group of bacteria of the same species allocated from various 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 is a group of bacteria that are the offspring of a single cell.

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Systematics of microorganisms.

Page 1 of 26Next ⇒

Systematics- distribution of microorganisms according to their origin and biological similarity.

Systematics deals with a comprehensive description species organisms, elucidating the degree of kinship between them and combining them into classification units of different levels of kinship - taxa. The main issues addressed in systematics (three aspects, three whales of systematics) - classification, identification and nomenclature.

Classification- distribution (association) of organisms in accordance with their common properties (similar genotypic and phenotypic characters) among different 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 the modern view species in microbiology

It is based on the use of the maximum number of compared features and mathematical accounting for 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.

pp.1-12), various genetic methods are used more and more widely and effectively (study of the genotype - genotypic properties).

Medical microbiology. Medical microbiology

Identification.

Nomenclature-

Strain serotypes (serovariants) abbreviated serovars) fagotypes, biochemical properties - chemovars biovars etc.

The colony- a visible isolated structure during the reproduction of bacteria on dense nutrient media, it can develop from one or more parental cells.

If the colony developed from one parent cell, then the offspring is called clone.

culture

cultures.

Morphology of bacteria.

.

micron) x 2-3 µm.

2. Rod-shaped.

3.Corrected.

4. Filiform.

coccoid 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 each).

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.Staphylococci(from lat. - a bunch of grapes).

They divide randomly in different planes, forming clusters resembling bunches of grapes. They cause numerous diseases, primarily purulent-inflammatory.

2.Bacilli - aerobic spore-forming microbes.

The spore diameter usually does not exceed the size (“width”) of the cell (endospore).

It must be borne in mind that the term "bacterium" 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

gliding-

Shie 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-intestinal coli

including spiral shape Spirillum

Yersinia Francisella,

Haemophilus, Borde-

coli

facultative anaerobes Escherichia, Salmone-

lla, Shigella, Klebsiel-

la, Proteus, Vibrio

12345678910Next ⇒

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Classification, or systematics 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".

At present, there is no universal, only correct classification.

Depending on the task, micro-organisms can be classified by morphological features (rods, cocci, convoluted, etc.), by tinctorial features (gram-positive, gram-negative, etc.), by physiological features (thermophilic , psychrophilic, acidophilic, aerobic, etc.), according to ecological characteristics (nitrogen-fixing, nitrifying, sulfate-reducing, cellulose-destroying, etc.), according to interspecific relationships (antagonists, synergists, commensals, etc.), according to taxis species, genotypic and phylogenetic characters.

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:

Characterization of microorganisms- Obtaining all kinds of information about the properties and parameters necessary to assign the determined microorganisms to a particular taxon.

Classification or taxonomy, i.e. the process of ordered arrangement of microorganisms into taxonomic groups based on similarity.

3. Nomenclature— assignment of scientific names to taxonomic groups (taxons).

The basic taxonomic unit in the taxonomy of micro-organisms is view.

According to general biological concepts, a species is a group of organisms close to each other, having a common root of origin and at this stage of evolution characterized by certain morphological, biochemical and physiological features, isolated by selection from other species and adapted to a specific habitat. An important species trait 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 mode of reproduction.

According to modern concepts, closely related organisms, with a 70% level of DNA homology and similar in terms of morphological, biochemical and physiological characteristics, are classified as one type of bacteria.

In the hierarchical classification of microorganisms, the following taxonomic categories are also used: subspecies- a group of closely related similar organisms inside kind with a level of DNA homology above 70%; genus- a taxonomic group that combines related species, and further - family, suborder, order, subclass, class, realm and domain(or supra-kingdom).

At present, families and domains are mostly described, while other taxonomic groups are in the process of systematization.

Domains are the highest taxa of microorganisms, corresponding to previously identified 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 supra-kingdom — Procariolae.

Fig.2. Universal phylogenetic tree of living organisms.

The most accurate, informative, and user-friendly classification system is one in which taxa are defined based on a variety of consistent characteristics obtained using various modern methods.

A similar approach to the selection of 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 the belonging of a microorganism to a certain species, the level of similarity of nucleotide sequences of DNA of about 70% plays a paramount role. Therefore, the genotypic method is often called the method of genomic fingerprinting.

Phenotypic studies are used most often in various schemes for the identification of microorganisms, for the formal description of a taxon, from variety and subspecies to genus and family.

While genotypic data is necessary to place a taxon on a phylogenetic tree and in a classification system, phenotypic characterization provides descriptive information that allows identification of a particular microorganism species. Classical phenotypic characteristics include morphological, physiological, biochemical, chemotaxonomic and serological characteristics of microorganisms.

Morphological features indicate what size and shape the microorganism has (coccus, bacillus, spirilla), whether it has a capsule or spores, whether cells are combined into chains, tetrads or packages, whether they have flagella and how they are located, whether they stain Gram cells.

The morphology of bacteria includes the study of cultural properties, i.e. the nature of growth on nutrient media, the shape of colonies on dense 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 signs are determined by the ability of micro-organisms to decompose certain sugars, form hydrogen sulfide, ammonia and other compounds.

Chemotaxonomic features characterize the chemical composition of the cell cytoplasm.

The 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 the identification of the variability of the antigenic components of bacterial cells.

Such components can be flagella, fimbriae. capsules, cell wall, enzymes and toxins. To identify the antigenic properties of a bacterial cell, various serological reactions are used: precipitation reaction, complement bonding reaction, precipitation, etc.

Thus, phenotypic characteristics are distinguished by a large volume and variety of information obtained, which is difficult to process manually.

There was a need for a computer, numerical analysis of the data obtained. Numerical (numerical) taxonomy has appeared, which allows using computer programs to analyze the phenotypic and genotypic characteristics of microorganisms. The use of numerical 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 in general and their individual taxonomic groups: species, subspecies, genera, families, suborders, orders , subclasses, classes, realms and domains.

Phylogenetic relationships between microorganisms are studied by the methods of genomic fingerprinting, molecular biology, and computer identification.

Based on the obtained data, phylogenetic trees are built, which reflect the evolutionary relationships between microorganisms (Fig. 3). The created phylogenetic trees cannot be used to build a hierarchical classification of microorganisms and do not replace systematics. They are one of its elements.

Nomenclature- deals with issues of precise and uniform names. Ego is a system of names used in a certain field of knowledge.

In accordance with international rules, taxonomic groups of microorganisms are assigned names.

Even before the introduction of the first rules of nomenclature, a huge number of microorganisms were described. Moreover, the same bacterium could be assigned to taxa with different names. To avoid this, the International Code of Nomenclature defined all the priority names of bacteria published since May 1, 1753. As a result, a "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 the scientific names of microorganisms. Classification issues are resolved regardless of the Code on the basis of ongoing taxonomic studies.

3. Phylogenetic tree of bacteria.

In microbiology, as in biology, a double (binary) nomenclature, proposed as early as 1760 by Carl Linnaeus, is adopted to designate bacterial species.

The first word is the genus name. Usually this is a Latin word, it is written with a capital letter and characterizes some morphological or physiological feature, or the name of the scientist who discovered this microbe. For example, in honor of the French scientist L. Pasteur, the genus "Pasteurella" is named, the American microbiologist Salmon - the genus "Salmonella", the German scientist T.

Escherichia - the genus "Esherichia", the Japanese microbiologist Shiga - the genus "Shigella", the English bacteriologists D. Bruce and S. Erwin - the genera "Brucella" and "Ervinia", the Russian scientists Kuznetsov and Lyambl - the genera "Kuznetsovia" and "Lamblia" and etc. The name of the microorganism genus is usually abbreviated to one or two letters.

The second word denotes a specific epithet in the name of a microorganism and, as a rule, is a derivative of a noun that describes the color of the colony, the source of origin of the microorganism, the process or disease it causes.

The species name is capitalized and never abbreviated. For example, Escherichia coli means that Escherichia live in the intestines, Pasterella pestis means Pasteurella that causes plague, Bordetetia pertussis means Bordetella that causes coughing, Clostridium tetani means Clostridium that causes tetanus, etc.

Vinogradsky and M. Beijerink, taking into account the diversity of bacterial metabolism, suggested that the genus name should reflect the features associated with morphology, ecology, biochemistry and physiology of microorganisms. This is how the names appeared, which are the key to the characterization of the microorganism: Acetobacter (acid-forming bacteria), Nitrosomonas (nitrifying bacteria), Azotobakter (bacteria that fix atmospheric nitrogen), Chromobacterium (pigmented bacteria), B.

stearothermophiliis (wax thermophilic bacteria), etc.

Sometimes, as an integral part of taxonomy, identification(definition) of microorganisms. However, this is not entirely correct, since identification uses already built 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. For the identification of microorganisms, phenotypic and genotypic methods, methods of computer identification analysis and genomic fingerprinting are widely used.

In 1923 D.

Burgey released the first international bacterial determinant. Subsequent editions have been prepared by the International Committee on the Systematics of Bacteria. The ninth and last US 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 towards attempts to identify microorganisms isolated from the environment.

According to BMDB-9, bacteria are classified (based on phenotypic traits) into four main categories:

1. Gram-negative eubacteria with cell walls.

2. Gram-positive eubacteria with cell walls.

Eubageria lacking cell walls.

4. Archaebacteria.

The main object in the identification of microorganisms is a pure culture of an isolated bacterium, called a "strain" or "clone".

Strain(from him.

stammen - 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 one species are adapted to a particular habitat.

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. The culture of microorganisms grown on a dense or liquid nutrient medium from individuals of the same species by successive reseeding 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 called a culture of heterogeneous microorganisms isolated from the material under study, for example, from water, soil, air.

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Systematics is a science dealing 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- this is an evolutionarily established set of individuals of the same genotype with similar morphological, physiological, cultural, biochemical and other features.

Species in microbiology are divided into subspecies or variants, strains and clones. Bacteria options differ in their individual features: morphological (morphovars), biological (biovars), enzymatic (enzyme products), resistance to antibiotics (resistensvars) and bacteriophages (phage vars), antigenic structure (serovars), pathogenicity for certain hosts (pathovars).

Strain- this is a culture of microbes isolated from a specific source (human body, animal, environment) by different authors and at different times.

Taxonomy of bacteria

Clone- a culture of microorganisms obtained from a single 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 family ties between organisms (taxonomy of higher organisms) and practical(artificial), the purpose of which is to identify the degree of similarity between microorganisms for rapid identification and assignment to certain taxa.

The modern taxonomy of microorganisms is based on the following features:

Morphological:-shape, Gram stain, mobility, spore and capsule formation, dimensions;

2. Biochemical: type of metabolism, fermentation of sugars and polyhydric alcohols, proteolytic properties, etc.

3. Physiological: relation to sources of C, O, nitrogen, temperature, pH, humidity;

Cultural features: the nature of growth on solid and liquid media;

5. Molecular biological(features of the structure of DNA).

At present, the international taxonomy of bacteria according to Bergi is accepted. Bergi is an American scientist who led the school of microbiologists, who, under his leadership, compiled the systematics of prokaryotes. Its first edition ("Guide to the Systematics of Bacteria") was published in 1923, the ninth - I t in 1984, 2 t - in 1986, 3 t - in 1989.

According to this systematics, 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 filaments.

3. Tenericute s - (tenes - soft, gentle).

The division includes mycoplasmas, which 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 are the following taxa: class, group(or section) order(suffix - ales), family(- ceae), genus, kind.

In microbiology, the binomial nomenclature proposed by K. Linnaeus is used: the first word means 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 features or the surname of the author who studied this genus. The species name is a description of the colony (color, shape) or source of origin.

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The taxonomy of microorganisms is extremely complex. Many microorganisms have the same morphological features, 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. Usually, microorganisms that have common morphological and physiological properties and are similar in antigenic structure are referred to one species.

In the habitat, the microorganisms that make up this species cause similar processes as a result of their vital activity. The name of the species in microorganisms is given according to the binomial (double) nomenclature proposed by Linnaeus in 1760.

1. Systematics of microorganisms.

The first word in the name of a microorganism means 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 is written with a lowercase letter, for example Bacillus anthracis - anthrax, 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 the scientists who discovered them can be reflected in the name of microorganisms. Thus, Brucella was described by the English scientist Bruce, Giardia by the Russian doctor Lyamble. In honor of the American microbiologist Salmon, the genus Salmonella is named, the German scientist Escherich - the genus Escherichia, the Japanese microbiologist Shiga - the genus Shigella.

Sometimes the name of microorganisms is associated with the name of the organ they infect: for example, meningococci cause damage to the meninges, pneumococci cause damage to the lungs, etc. These names are not consistent with the rules of nomenclature.

Systematics of microorganisms

Systematics - the distribution of microorganisms in accordance with their origin and biological similarity. Systematics deals with a comprehensive description of the species of organisms, elucidating the degree of kinship between them and combining them into classification units of different levels of kinship - 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 a microorganism. Classification is the distribution (association) of organisms in accordance with their common properties (similar genotypic and phenotypic characters) among various taxa.

Taxonomy is the science of methods and principles of distribution (classification) of organisms in accordance with their hierarchy.

The following taxonomic units (taxa) are most often used - strain, species, genus. Subsequent larger taxa - family, order, class. In the modern view 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 compared features and mathematical consideration of the degree of correspondence.

A large number of compared phenotypic traits and the principle of their equal significance 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 mutual arrangement, structure.

2. Tinctorial - the attitude to various dyes (the nature of staining), primarily to Gram stain.

On this basis, all microorganisms are divided into gram-positive and gram-negative.

Morphological properties and attitude to Gram staining usually make it possible to attribute the studied microorganism to large taxa - a family, a 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.), to form various biochemical products in the process of life due to the activity of various enzyme systems and metabolic features.

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.

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. The ability to form spores, 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.

Protein spectrum (polypeptide profile).

12. Sensitivity to antibiotics and other drugs.

13. Genotypic (use of methods of genosystematics).

Classification of microorganisms

The classification of microorganisms (root taxon) is the distribution of microorganisms according to similar or distinctive features into ordered groups.
The classification of microorganisms is one of the most difficult branches of microbiology.

The more complete our knowledge of 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 particular microorganism must consistently belong to all 7 categories.

kingdom (lat.

regnum) is a hierarchical level of 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, one more thing has been distinguished: chromium.

Division (lat. dvisio) is one of the highest ranks of the taxonomic hierarchy in microbiology. In the hierarchy of taxonomic categories, the department is above the class and below the kingdom.
The names of departments, like the names of other taxa, the rank of which 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 division and above order. The class names, like the names of other taxa higher than the genus, are uninomial. Order (Latin ordo) is one of the main ranks of the hierarchical classification. In the hierarchy of systematic categories, it is below the class and above the family. In bacteriology, the standardized ending -ales is used to name the orders.

Carl Linnaeus expressed the opinion that "order is a subdivision of classes, introduced in order not to distinguish between genera in a number greater than they can easily be perceived by the mind." family (lat.

familia) is one of the main ranks of the hierarchical classification in biological systematics. In the hierarchy of systematic categories, the family is lower than the order and higher than the genus. The names of families are formed according to the rules regulated by the International Code of Nomenclature for Bacteria. The name of the family is formed from the name of the type genus, to the base of which the standard ending aceae is added.

Genus (Latin genus) is one of the main ranks of hierarchical classification in biological systematics.
In the hierarchy of systematic categories, the genus is below the family and above the species. The scientific name of the genus is uninomial, that is, it consists of one word. The codes of biological nomenclature require that this word be Latin in form, that is, written in the letters of the Latin alphabet and subject to the rules of Latin grammar.

The genus name is treated as a singular noun and is capitalized. 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 name of the genus is a word formed from a surname or a given name (for example, Escherichia) from the name of the scientist Escherich.

From the basis of the generic name, the names of the taxa of the family group are formed. The rules for the formation and use of generic names are established by the rules set forth in the International Code of Nomenclature for Bacteria. A species (lat. species) is a taxonomic, systematic unit, a group of individuals with common morphophysiological, biochemical and behavioral characteristics, capable of interbreeding, producing fertile offspring in a number of generations, regularly distributed within a certain area and similarly changing under the influence of environmental factors.

A species is a real-life unit of the living world, the main structural unit in the system of organisms. In the classification of microorganisms, the species problem is the most important and difficult. Without a species definition, it is impossible to build a classification.

A species is a set of microorganisms that have a common origin and genotype, similar morphological and biological properties.

The species of bacteria is determined by the sum of various features 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. A pure culture is a set 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 distinct from other members of the species.
A clone is a collection of offspring 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 under study. Relatively new is the concept of supra-kingdom, or biological domain.

It was proposed in 1990 by Carl Woese and introduced the division of the entire biomass of the Earth 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 unicellular organisms, they are divided into two distinct groups: eukaryotes and prokaryotes.
Eukaryotes are higher microorganisms, or protists.

Their cells are structurally similar to plant and animal cells. Eukaryotes include algae, fungi and protozoa. Eukaryotic cells have a differentiated nucleus separated from the cytoplasm by a nuclear membrane. Inside the nucleus is a set of chromosomes, which, doubling in the process of division - mitosis, are transferred to daughter cells. In the cytoplasm of eukaryotes, there is 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 differ sharply in their structure from all other living organisms. In the cell wall of prokaryotes, peptidoglycans (glycoproteins) were found that were not found in the composition of eukaryotic cells. The nucleus of a prokaryotic cell is not differentiated: deoxyribonucleic acid (DNA), which makes up the chromosome, is freely immersed in the cytoplasm, the nuclear membrane is absent. The endoplasmic reticulum is poorly developed, so the division into "compartments" in the cytoplasm is not pronounced.

Until now, there is no unified international classification of microorganisms. Mushrooms, protozoa and viruses have their own specific classification, which will be presented in the relevant sections.

There are also various classification schemes for bacteria and blue-green algae. Currently, Bergey's taxonomy, set forth in the "Key to Bacteria", last published in 1974, is gaining increasing recognition. More than 1,500 species of microorganisms belonging to prokaryotes are described and systematized in it.

Microorganisms related to prokaryotes, in Bergey's definition, are divided into two sections: I - cyanobacteria (blue-green algae) and II - bacteria. The department of bacteria is described and systematized in the most detailed way. It includes, in addition to bacteria proper (cocci, bacilli, spirilla), microorganisms such as spirochetes, actinomycetes, rickettsia, chlamydia, mycoplasmas. The bacteria department is divided into 19 groups, or parts, which corresponds 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), mycoplasmas (group 19).

Microorganism identification

The main phenotypic and genotypic characteristics used for the classification of microorganisms are also used for identification, i.e. establishing their taxonomic position and, above all, their species, the most important aspect of the microbiological diagnosis of infectious diseases. Identification is carried out on the basis of studying the phenotypic and genotypic characteristics of the studied infectious agent and comparing them with the characteristics of known species.

In this work, reference strains of microorganisms, standard antigens and immune sera to known prototype microorganisms are often used. Pathogenic microorganisms often study morphological, tinctorial, cultural, biochemical and antigenic properties.

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 (with a lowercase letter). Examples are 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 the same species, isolated simultaneously from one source: from a patient or carrier, as well as from environmental objects (from water, food, household items). The strains differ from each other in individual characteristics, such as resistance to antibiotics, sulfonamides, the ability to cause an infectious disease of varying severity, clinical course and outcome. However, strains of one species have all the features 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 given strain was isolated, or the name of the territory in which it was found. For example, different strains of the influenza virus are named after the place of their isolation: the "Asian" strain of the influenza virus, the "Hong Kong" strain of the influenza virus.

Clone - a culture of microorganisms obtained by reproduction of one cell of a given species or strain.

The term "culture" or "population" is used to refer to a set of microbes growing on a nutrient medium from one or more cells of the same species (from the French population - population). A population of microbes consisting of individuals of the same species is called a pure culture, and of individuals of different species - a mixed culture.

The basic principle of bacteriological work is isolation and study of the properties of only pure(homogeneous, without admixture of foreign microflora) cultures.

1 2 3 4 5 6 7 8 9 10

Numerical (numerical) taxonomy is based on the use of the maximum number of compared features and mathematical consideration of the degree of correspondence. A large number of compared phenotypic traits and the principle of their equal significance made classification difficult.

When studying, identifying and classifying microorganisms, the following (geno- and phenotypic) characteristics are most often studied:

1. Morphological - form, size, features of relative position, structure.

2. Tinctorial - relation to various dyes (the nature of staining), primarily to Gram stain.

On this basis, all microorganisms are divided into gram positive and gram negative.

Morphological properties and attitude to Gram staining allow, as a rule, to attribute the studied microorganism to large taxa - a family, a 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.), to form various biochemical products in the process of life due to the activity of various enzyme systems and metabolic features.

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 food, 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 methods of genosystematics).

In recent decades, for the classification of microorganisms, in addition to their phenotypic characteristics (see paragraphs 1-12), various genetic methods are increasingly and effectively used (study of the 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, more often they proceed from the conditional assumption that the degree of homology of more than 60% (for some groups of microorganisms - 80%) indicates that microorganisms belong to the same species (different genotypes - one genotype), 40-60% - to the same genus.

Identification.

The main phenotypic and genotypic characteristics used for the classification of microorganisms are also used for identification, i.e.

establishing their taxonomic position and, above all, their species, the most important aspect of the microbiological diagnosis of infectious diseases. Identification is carried out on the basis of studying the phenotypic and genotypic characteristics of the studied infectious agent and comparing them with the characteristics of known species.

In this work, reference strains of microorganisms, standard antigens and immune sera to known prototype microorganisms are often used. Pathogenic microorganisms often study morphological, tinctorial, cultural, biochemical and antigenic properties.

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 (with a lowercase letter). Examples are Shigella flexneri, Rickettsia sibirica.

In microbiology, a number of other terms are often used to characterize microorganisms.

Strain— any specific specimen (isolate) of a given species. Strains of the same species that differ in antigenic characteristics are called serotypes (serovariants) abbreviated serovars), by sensitivity to specific phages- fagotypes, biochemical properties - chemovars, according to biological properties - biovars etc.

The colony- a visible isolated structure during the reproduction of bacteria on dense nutrient media, it can develop from one or more parental cells. If the colony developed from one parent cell, then the offspring is called clone.

culture- the whole set of microorganisms of the same species grown on a solid or liquid nutrient medium.

The basic principle of bacteriological work is isolation and study of the properties of only pure(homogeneous, without admixture of foreign microflora) cultures.

Morphology of bacteria.

Prokaryotes differ from eukaryotes in a number of key ways..

1. Absence of a true differentiated nucleus (nuclear membrane).

2. The absence of a developed endoplasmic reticulum, the Golgi apparatus.

3. Absence of mitochondria, chloroplasts, lysosomes.

4. Inability to endocytosis (capture of food particles).

5. Cell division is not associated with cyclic changes in the structure of the cell.

Significantly smaller sizes (as a rule). Most of the bacteria have a size of 0.5-0.8 micrometers ( micron) x 2-3 µm.

According to the form, the following main groups of microorganisms are distinguished.

1. Spherical or cocci (from Greek - grain).

2. Rod-shaped.

3.Corrected.

4. Filiform.

coccoid bacteria (cocci)according to the nature of the relationship after division, they are divided into a number of options.

1.micrococci.

Cells are located alone. They are part of the normal microflora, are in the external environment. They do not cause disease 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. The division is carried out in one plane, the multiplying cells keep the connection (do not diverge), forming chains.

Many pathogenic microorganisms are the causative agents of tonsillitis, scarlet fever, purulent inflammatory processes.

4.Tetracocci. Division in two mutually perpendicular planes with the formation of tetrads (i.e., four cells each). 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.Staphylococci(from lat. - a bunch of grapes). They divide randomly in different planes, forming clusters resembling bunches of grapes.

They cause numerous diseases, primarily purulent-inflammatory.

rod-shaped microorganisms.

1. Bacteria are rods that do not form spores.

2.Bacilli - aerobic spore-forming microbes. The spore diameter usually does not exceed the size (“width”) of the cell (endospore).

3. Clostridia - anaerobic spore-forming microbes. The diameter of the spore is greater than the diameter (diameter) of the vegetative cell, and therefore the cell resembles a spindle or a tennis racket.

It must be borne in mind that the term "bacterium" 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.

Convolute forms of microorganisms.

1. Vibrio and campylobacter - have one bend, can be in the form of a comma, a short curl.

2.Spirilli - have 2-3 curls.

3. Spirochetes - have a different number of curls, axostyle - a collection of fibrils, a specific character of movement for various representatives and structural features (especially the end 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, a more detailed description 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 Berge Bacteria Key.

Key to major groups of bacteria

The main groups of bacteria | genera of bacteria

1. Bending bacteria with thin walls, mobile

nost is provided due to sliding - gliding-

living bacteria

2. Bending bacteria with thin walls, mobile - Treponema

ness is associated with the presence of an axial thread spirochetes Borrelia, Leptospira

3. Rigid bacteria with thick walls, motionless

nye or mobile due 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

including obligatory aerobes Bacillus

including obligatory Clostridium anaerobes

b. gram negative:

cocci Neisseria

non-intestinal coli

spiral shape Spirillum

including straight, very small sticks Pasteurella, Brucella,

Yersinia Francisella,

Haemophilus, Borde-

coli

including facultative anaerobes Escherichia, Salmone-

lla, Shigella, Klebsiel-

la, Proteus, Vibrio

including obligate aerobes Pseudomonas

including obligate anaerobes Bacteroides, Fuso-

4. Without cell walls Mycoplasma, Urea-

3. Structure of a bacterial cell.

The essential organelles are: nuclear apparatus, cytoplasm, cytoplasmic membrane.

Optional(minor) structural elements are Key words: 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 strand of DNA. The nucleoid is not separated from the cytoplasm by a nuclear membrane.

2.Cytoplasm- a complex colloidal system containing various inclusions of metabolic origin (granules 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, formation of the intercellular septum during division).

3.cytoplasmic membrane limits the cytoplasm from 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- 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, first of all, it provides mechanical protection and a permanent shape of cells; 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 for bacteria - peptidoglycan(mureic acids). An important feature of bacteria for taxonomy 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 retains the iodine complex after Gram staining. gentian violet(stained blue-violet), gram-negative bacteria lose this complex and the corresponding color after treatment and are stained pink by staining with fuchsin.

Features of the cell wall of gram-positive bacteria.

Powerful, thick, uncomplicatedly organized cell wall, which is dominated by peptidoglycan and teichoic acids, no lipopolysaccharides (LPS), 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, contains LPS, lipoproteins, phospholipids, diaminopimelic acid.

It is more complicated - there is an outer membrane, so the cell wall is three-layered.

When processing gram-positive bacteria with enzymes that destroy peptidoglycan, there are structures completely devoid of a cell wall - 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 adverse conditions of existence. As a result of a change in antigenic properties (loss of O- and K-antigens), a decrease in virulence and other factors, L-forms acquire the ability to stay for a long time ( persist) in the host organism, maintaining a sluggish infectious process.

The loss of the cell wall renders the L-forms insensitive to antibiotics, antibodies, and various chemotherapeutic agents whose point of application is the bacterial cell wall.

Unstable L-shape 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 them into 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 related to mycoplasmas, 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 a cell wall), include capsule, flagella, microvilli.

Capsule or mucous layer surrounds the shell of a number of bacteria.

Allocate microcapsule, detected by electron microscopy in the form of a layer of microfibrils, and macrocapsule detected 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. At saprophytes capsules are formed in the external environment, in pathogens, more often in the host organism. 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 Guinsu), less often - from polypeptides.

Flagella. Motile bacteria can be gliding (moving on a solid surface as a result of wave-like contractions) or floating, moving due to filamentous spirally bent protein ( flagellic according to the chemical composition) formations - flagella.

According to the location and number of flagella, a number of forms of bacteria are distinguished.

1. Monotrichous - have one polar flagellum.

2. Lofotrichous - have a polar bundle of flagella.

3. Amphitrichous - have flagella at diametrically opposite poles.

4. Peritrichous - have flagella around 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 that surround the bacterial cell in large numbers, with the help of which bacteria are attached to substrates (for example, to the surface of mucous membranes).

Thus, the fimbriae are adhesion and colonization factors.

F-drank (fertility factor)- apparatus bacterial conjugation, are found in small quantities in the form of thin protein villi.

Endospores and sporulation.

sporulation- a way to preserve certain types of bacteria in adverse 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 adverse environmental factors. Light microscopy is often used to detect spores. according to Orzeshko. High resistance is associated with a high content calcium salt of dipicolinic acid in the spore shell.

The location and size of spores in different microorganisms is different, which has a differential diagnostic (taxonomic) value. The main phases of the “life cycle” of spores sporulation(includes the preparatory stage, the prespore stage, the formation of the shell, maturation and dormancy) and germination ending with the formation of a vegetative form. The process of sporulation is genetically determined.

Uncultivated forms of bacteria.

Many species of gram-negative bacteria that do not form spores have a special adaptive state - uncultivated forms.

They have low metabolic activity and do not actively multiply; do not form colonies on dense nutrient media, are not detected during crops. They are highly resistant and can remain viable for several years. Not detected by classical bacteriological methods, detected only by genetic methods ( polymerase chain reaction - PCR).

Microbiology: lecture notes Tkachenko Ksenia Viktorovna

2. Systematics and nomenclature of microorganisms

The main taxonomic unit of bacterial taxonomy is the species.

A species is an evolutionarily established set of individuals that has a single genotype, which under standard conditions is manifested by similar morphological, physiological, biochemical and other features.

The species is not the final unit of taxonomy. Within the species, variants of microorganisms are distinguished that differ in individual characteristics. So, they distinguish:

1) serovars (by antigenic structure);

2) chemovars (according to sensitivity to chemicals);

3) fagovars (by sensitivity to phages);

4) fermenters;

5) bacteriocinovars;

6) bacteriocinogenovars.

Bacteriocins are substances produced by bacteria that have a detrimental effect on other bacteria. According to the type of bacteriocin produced, bacteriocinovars are distinguished, and according to sensitivity, bacteriocinogenovars are distinguished.

For species identification of bacteria, it is necessary to know the following properties:

1) morphological (shape and structure of a bacterial cell);

2) tinctorial (the ability to stain with various dyes);

3) cultural (nature of growth on a nutrient medium);

4) biochemical (the ability to utilize various substrates);

5) antigenic.

Species related by genetic relationship are combined into genera, genera - into families, families - into orders. The higher taxonomic categories are classes, divisions, subkingdoms and kingdoms.

According to modern systematics, pathogenic microorganisms belong to the kingdom of prokaryotes, pathogenic protozoa and fungi - to the kingdom of eukaryotes, viruses are combined into a separate kingdom - Vira.

All prokaryotes that have a single type of cell organization are combined into one department - Bacteria. However, some of their groups differ in structural and physiological features. On this basis, there are:

1) actually bacteria;

2) actinomycetes;

3) spirochetes;

4) rickettsia;

5) chlamydia;

6) mycoplasmas.

Currently, a number of taxonomic systems are used for the taxonomy of microorganisms.

1. Numerical taxonomy. Recognizes the equivalence of all signs. To use it, it is necessary to have information about many dozens of features. The species affiliation is established by the number of matching characters.

2. Serotaxonomy. It studies bacterial antigens using reactions with immune sera. Most often used in medical bacteriology. The disadvantage is that bacteria do not always contain a species-specific antigen.

3. Chemotaxonomy. Physico-chemical methods are used to study the lipid, amino acid composition of a microbial cell and certain of its components.

4. Genetic systematics. Based on the ability of bacteria with homologous DNA to transform, transduce and conjugate, on the analysis of extrachromosomal factors of heredity - plasmids, transposons, phages.

The totality of the basic biological properties of bacteria can only be determined in a pure culture - these are bacteria of the same species grown on a nutrient medium.

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