Microorganisms are representatives of all kingdoms of life invisible to the naked eye.

• 1. Eukaryotes, or nuclear organisms (fungi, protozoa).
• 2. Prokaryotes, or prenuclear organisms (eubacteria, archaebacteria).
• 3. Acaryotes (nuclear-free organisms) - viruses.

Their classification is regulated by the relevant International Committees on Taxonomy. The classification of bacteria is constantly being improved, which is reflected in the periodicals “Burgee’s Determinant of Bacteria”. According to this book, all known bacteria are classified into the kingdom of prokaryotes and are divided into 4 divisions based on differences in the structure of the cell wall.

Division I. Gmcilicutes(from Latin gracilis - graceful, thin and cutis - skin): includes gram-negative bacteria.

Division II. Firmicutes(from Latin firmus - strong): includes gram-positive bacteria.

Division III. Tenericutes(from Latin tener - tender): includes bacteria lacking a cell wall (mycoplasma, etc.).

Division IV. Mendosicutes(from Latin mendosus - directed): includes archaebacteria that have a cell wall of a special composition and structure.

The bacteria are further divided into 17 parts, which contain representatives of various classes, families, genera and species. These groups are not formal taxonomic categories, but are intended to subdivide bacteria into easily identifiable phenotypic units. Further, within groups, bacteria are distributed according to obligatory taxa (class, order, family, genus, species). Bacteria pathogenic to humans belong to a limited number of groups.

Group 1. Spirochetes. Representatives of the genera are pathogenic for humans Borrelia, Leptospira, Treponema.

Group 2. Gram-negative, aerobic and microaerophilic, motile, convoluted and curved bacteria. Species pathogenic to humans are included in the genera Campylobacter, Helicobacter, Spirillum.

Group 3. Gram-negative, non-motile (rarely motile), curved bacteria. Does not contain species pathogenic to humans.

Group 4. Gram-negative, aerobic and microaerophilic rods and cocci. Species that are pathogenic and opportunistic for humans are included in the families Legionellaceae, Neisseriaceae, Pseudomonaceae and a number of genera Acinetobacter, Alcaligenes, Afipia, Bordetella, Brucella, Chryseomonas, Flavobacterium, Francisella, Moraxella, Oligella.

Group 5. Gram-negative, facultative anaerobic rods. Pathogenic and opportunistic species are included in the families Enterobacteriaceae, Vibrionaceae, Pasteurellaceae, as well as the genera Galymmatobacterium, Cardiobacterium, Eikanella, Gardnerella, Streptobacillus.

Group 6. Gram-negative, anaerobic, straight, curved and spiral bacteria. Pathogenic and opportunistic species are included in the genera Bacteroides, Fusobacterium, Porphyromonas, Prevotella.

Group 7. Bacteria that carry out the dissimilatory reduction of sulfate or sulfur. Does not contain species pathogenic to humans.

Group 8. Gram-negative, anaerobic, cocci. Includes opportunistic bacteria of the genus Veilonella.

Group 9. Rickettsia and chlamydia. Species pathogenic to humans contain families Rickettsiaceae, Bartonellaceae, Chlamydiaceae.

Group 10. Anoxygenic, phototrophic bacteria. Does not contain species pathogenic to humans.

Group 11. Oxygenic, phototrophic bacteria. Does not contain species pathogenic to humans.

Group 12. Aerobic, chemolithotrophic bacteria and related microorganisms. Does not contain species pathogenic to humans.

Group 13. Budding and (or) bacteria with outgrowths. Does not have species pathogenic to humans.

Group 14. Bacteria with a sheath. Does not contain species pathogenic to humans.

Group 15. Non-photosynthetic, non-forming fruiting bodies, gliding bacteria. Does not contain species pathogenic to humans.

Group 16. Sliding bacteria that form fruiting bodies: myxobacteria. Does not contain species pathogenic to humans.

Group 17. Gram-positive cocci. Contains pathogenic and opportunistic species of genera Enterococcus, Leuconostoc, Peptococcus, Peptostreptococcus, Sarcina, Staphylococcus, Stomatococcus, Streptococcus.

Group 18. Gram-positive, spore-forming rods and cocci. Includes pathogenic and opportunistic types of genera

Clostridium And Bacillus.

Group 19. Gram-positive, regular-shaped, non-spore-forming rods. Includes opportunistic genera

Erysipelothrix, Listeria, Kurthia.

Group 20. Gram-positive, irregularly shaped, non-spore-forming rods. Contains pathogenic and opportunistic species of genera Actinomyces, Corynebacterium, Gardnerella, Mobiluncus.

Group 21. Mycobacteria. Contains a single gender Mycobacterium, containing pathogenic and conditionally pathogenic species for humans.

Group 22. Nocardioform actinomycetes. Contains pathogenic and opportunistic species of genera Gordona, Nocardia, Rhodococcus, Tsukamurella, Jonesia, Oerskovia, Terrabacter.

Groups 23-29. Actinomycetes. Do not contain pathogenic or conditionally pathogenic species for humans.

Group 30. Plasma mycos (mollicutes): bacteria without a cell wall. Species pathogenic to humans are included in the genera Acholeplasma, Mycoplasma, Ureaplasma.

Groups of archaebacteria: 31 (methanogens), 32 (sulfate-reducing archaea), 33 (extreme halophilic, aerobic bacteria, halobacteria), 34 (archaebacteria lacking a cell wall), 35 (extreme thermophiles and hyperthermophiles that metabolize sulfur). Do not contain species pathogenic to humans.

Classification is needed to clarify the related relationships between bacteria, uniting them into interconnected and subordinate groups (taxa). Microbiology as a science arose earlier than genetics. Therefore, the classification of bacteria was initially based solely on the study of their phenotypic characteristics. Based on the methods of phenosystematics, the traditional (artificial) classification of bacteria was formed. Phenosystematics studies the taxonomic characteristics of microorganisms, i.e. any signs by which it is possible to establish the similarities and differences between classified groups of microorganisms. It is also customary to identify key taxonomic characters (the most significant, little varying).

Taxonomic characters include:

• morphology of bacterial cells;
• mobility;
• sporulation;
• cultural characteristics;
• tinctorial properties (relation to Gram stain);
• physiological properties (types of metabolism, spectra of fermentation or utilization of substrates, relation to oxygen);
• antigenic structure of cells;
• chemical composition of cells (fatty acid and lipid composition, protein spectra, etc.);
• sensitivity to bacteriophages and antibiotics.

At the same time, phenosystematics has a number of significant drawbacks: subjectivity in the selection of the studied traits and their evaluation, the dependence of the manifestation of traits on the conditions of their study (phenotypic variability), low information content (phenotypically manifested 5-20% genome information).

In order to increase the information content and objectivity of the study at the end of the 20th century. Numerical taxonomy was developed. Numerical taxonomy is used in scientific taxonomic research, and in practical work, microorganisms are identified using a limited set (20-30) of key taxonomic characteristics.

More objective is the construction of a natural (phylogenetic) classification of bacteria using the methods of gene systematics. Phenotype and genotype are inseparable components of the organism as a whole, therefore the methods of pheno- and genosystematics cannot be opposed. Genosystematics studies the organization of genomes, i.e. genetic programs of organisms. The object of her research is cell DNA. The first method of gene systematics, developed in 1956-57. domestic scientists A.N. Belozersky and A.S. Spirin and the staff of the Pasteur Institute in Paris (K. Lee, R. Weil, E. Barbue), consisted of determining the guanine-cytosine coefficient, i.e. the ratio of the molar percentages of guanine (G) and cytosine (C) of the nucleotide composition of the total DNA of a microorganism. It was determined by the melting temperature of DNA or spectrophotometrically. Currently, gene systematics uses a number of methods that make it possible to identify the relatedness of microorganisms at various taxonomic levels and study their evolutionary relationships. Genetic analysis methods include:

• 1) DNA-DNA molecular hybridization (method for detecting DNA homology). The method allows us to identify relationships at the species and genus level. With a degree of homology of 70% or more, bacteria belong to the same genospecies;
• 2) molecular hybridization of DNA with ribosomal RNA. The method reveals kinship at the level of genus and family;
• 3) DNA sequencing - determination of the nucleotide sequence of genes or fragments (oligonucleotides) of DNA. The method makes it possible to identify evolutionary relationships at the level of kingdom, division, class, family, genus, but is not sensitive enough at the species level;
• 4) DNA restriction analysis (“fingerprinting”). The method allows intraspecific typing of bacteria.

According to the International Code of Nomenclature of Bacteria, the scientific language is Latin. Taxonomic categories are divided into mandatory and optional.

Mandatory taxa (descending order):

• Kingdom (Regium);
• Class (Classis);
• Order (Ordo);
• Family (Familia);
• Genus;
• Species.

Optional taxa (descending):

• Subclass (Subclassis);
• Subfamily (Subfamilia);
• Tribus:
• Subtribe (Subtribus);
• Subgenus (Subgenus);
• Subspecies.

The names of taxa above the species are written as one word with a capital letter and a suffix corresponding to the taxon. Gender is indicated by one capitalized word (singular noun). A species is designated by a binary (binomial) combination consisting of the genus name (with a capital letter) and the specific epithet (with a lowercase letter). When first mentioned in the text, the full name of the species is given. When used again, the generic word is shortened to the first letter, but the specific epithet is retained completely. For example, Yersinia pestis And Y. pestis. A specific epithet is given arbitrarily, but more often based on the origin of the species, its special property, or in honor of the scientist who described the species. Usually the specific epithet is a noun in the genitive case, for example Shigella sonnei.

A species may have subspecies. To designate them, a triple combination is used, consisting of the name of the genus, specific and subspecific epithets. To distinguish between specific and subspecific epithets, the abbreviated word subsp is placed before the latter. (from lat. subspecies - subspecies), for example, Klebsiella pneumoniae subsp. ozenae. A species can also have varieties (varietas): serovars, biovars, chemovars, etc., for example, Vibrio cholerae biovar eltor. The term strain refers to an isolate of a microorganism obtained from different sources or at different times. It is designated by protocol number or by source of isolation. The term “clone” refers to a culture of microorganisms obtained from a single cell. A pure culture is a population of microorganisms consisting of individuals of one species.

A list of the names of all studied (published) bacterial species is presented in the publication of the International Committee on the Taxonomy of Bacteria. Unfortunately, in microbiology there is still no clear, generally accepted definition of the most important taxonomic category of bacterial species. This is due to the lack of reliable species criteria for prokaryotes. The criteria used to determine species in plants and animals are not suitable for bacteria. The term “species” in bacteria should be understood as the closest community characterized by a similar content of GC pairs.

Identification - determining whether the bacteria under study belong to a known taxon. For identification, it is necessary to have a pure culture of the bacteria being studied. It is obtained by seeding bacteria on the surface of solid nutrient media using a technique that ensures the growth of isolated colonies. A bacterial colony is the offspring of a single isolated cell containing a pure culture. However, a colony does not always contain the offspring of one cell. To ensure the purity of the culture, it is advisable to repeat sieving from one colony on nutrient media without inhibitors.

Given the high phenotypic variability of bacteria, it is necessary to use standardized test methods for identification. It is advisable to use a minimum number of the most important and easily performed tests. First, tests are used to determine whether bacteria belong to a certain department and group according to the Bergey Bacteria Identifier, for example, morphology, Gram stain, motility, presence of spores, relationship to oxygen. Then the most important tests characterizing the proposed taxon (genus, species) are used.

The most important thing for identification is the determination of the biochemical characteristics of bacteria. They are determined mainly by microvolume technology using commercial test systems or automatic identification system devices corresponding to the taxon. Serological reactions aimed at identifying bacterial antigens and their taxa are also widely used for identification.

The totality of the information obtained about the properties of bacteria is compared with the characteristics of certain taxa in the “Burgee's Guide to Bacteria” or other manuals and a conclusion is drawn about the taxonomic position of the bacteria.

In recent years, methods of genoindication of microorganisms that do not require the isolation of pure cultures have been increasingly used: the method of DNA probes, polymerase chain reaction (PCR) with specific primers. These methods are highly sensitive and allow you to quickly identify microorganisms directly in the material under study.

Lecture No. 1

Introduction. Principles of classification of microbes. Organization

microbiological service.

For the specialties “Nursing”, “General Medicine”, “Midwifery”,

"Pharmacy",

1. Concept and microbiology. Sections of microbiology.

2. Brief historical outline of development.

3. Principles of classification of microorganisms.

4. Morphology of bacteria.

5. Structure of a bacterial cell.

Concept of microbiology

Microbiology is the science of microorganisms, tiny creatures invisible to the eye. Microbes are the very first inhabitants of our planet, playing both positive and negative roles in human life.

The importance of microbes in nature:

· Microbes are of paramount importance in the circulation of substances in nature. If there were no microbes, the Earth would be littered with the remains of dead animals and plants.

· People use the beneficial properties of microbes in the production of beer, wine, and in baking.

· Microbes are used to obtain medicines (antibiotics, vitamins, enzymes, etc.).

· At the same time, many microbes are pathogenic for humans. They are the subject of study of medical microbiology.

Sections of microbiology

· Industrial microbiology.

· Agricultural.

· Marine.

· Space.

· Veterinary.

· Medical.

· Sanitary (microecology).

History of the development of microbiology

The first information about microorganisms appeared in the 17th century - Italian scientist Girolamo Fracostoro made the assumption that the cause of infectious diseases is the smallest animals invisible to the eye, which he called “contagia” (hence the word contagiousness). The development of microbiology began only after the invention of the microscope by the Dutch naturalist Antonio Leeuwenhoek. From this moment it began morphological (descriptive period in the development of microbiology.

But microbiology acquired truly scientific development only at the end of the 18th and 19th centuries, when pathogens of infectious diseases began to be discovered and physiological period. Robert Koch discovered the causative agents of anthrax, tuberculosis, and cholera. I.I. Mechnikov and Paul Ehrlich substantiated the theories of immunity. Louis Pasteur created vaccines against rabies and anthrax.

Classification of microorganisms

The modern classification of microorganisms was proposed in 1980 by an American microbiologist Burgee. To date, it has gone through 7 reprints, because... constantly changing and being supplemented.

· According to this classification, the entire world of microbes is divided into 3 kingdoms:

1. prokaryotes (microbes with an unformed nucleus),

2. eukaryotes (microbes with a formed nucleus)

3. viruses (non-cellular life form).

Within each kingdom there is a division into the following structural units:

kingdoms - divisions - classes - orders - families - genera - species. Thus, the species is the smallest structural unit.

But within the species there is a division into biovars, chemovars, serovars, phagevars, etc.

A species is a collection of microorganisms that have a common origin (genetic relatedness), morphological, physiological properties and metabolism substances.

The name of a microbe uses binary (double) nomenclature: the first word means genus and is written with a capital letter, the second word means species and is written with

small letter. For example, Staphylococcus aureus. Let us consider the most important classes of microorganisms included in the kingdoms.

Working classificationsmicroorganisms

· A) by the number of cells - all classes of microorganisms are unicellular, except fungi (most of them are multicellular)

· B) by origin- Most prokaryotes and eukaryotes are of plant origin, except protozoa (they originate from animal cells)

ORGANIZATION OF LABORATORY MICROBIOLOGICAL SERVICE

Object of study of medical microbiological laboratories -

pathogenic biological agents (PBA):

Microorganisms pathogenic to humans (viruses, bacteria, fungi, protozoa, etc.);

Genetically modified microorganisms;

Poisons of biological origin (toxins), helminths;

Biomaterial (including blood, biological fluids and human excrement) suspected of containing PBA.

Classification of microbiological laboratories according to the nature of the research performed:

 Diagnostic(conduct research to detect and identify the pathogen, its antigen or specific antibodies to it);

 Production(carry out departmental laboratory control of products manufactured by the enterprise for their compliance with regulatory documentation on sanitary indicative microorganisms.

 Research

Classification of microbiological laboratories according tostudied microorganisms

 Bacteriological;

 Virological;

 Mycological;

 Protozoological

Classification of pathogens of infectious diseases according to the degree of danger of working with them

 GRUnit I: pathogens of particularly dangerous infections: plague, smallpox, Lassa fever, Ebola, etc.

 GRUnit II: causative agents of highly contagious human epidemic diseases: anthrax, cholera, Rocky Mountain fever, typhus, blastomycosis, rabies, etc. This group also includes botulinum toxin (but not the causative agent of botulism itself)

 GRUnit III: causative agents of bacterial fungal, viral and protozoal infections, isolated into separate nosological forms (causative agents of whooping cough, tetanus, botulism, tuberculosis, candidiasis, malaria, leishmaniasis, influenza, polio, etc.). This group also includes attenuated strains of bacteria of groups I, II and III.

 GRUnit IV: opportunistic microbes- pathogens of opportunistic infections

Depending on the level of safety when working with microorganisms

laboratories are divided into four risk groups:

 First risk group: special regime laboratories (maximum

isolated) with high individual and public risk.  Second risk group: secure laboratories (isolated) with high individual and low public risk.

 Tthird risk group: basic (basic) laboratories with moderate

individual and limited public risk.

 Fourth risk group: basic (basic) laboratories with low

individual and public risk.

In the system of the Ministry of Health andGstate committeeWithAnitary and epidemiological surveillance of the Russian Federation has the most extensive network of bacteriological laboratories:

 bacteriological laboratories as part of health care facilities;

 bacteriological laboratories as part of the State Sanitary and Epidemiological Supervision committees;

 educational bacteriological laboratories of universities;

 problem and industry bacteriological laboratories

research institutes and enterprises producing

bacterial preparations;

 specialized bacteriological laboratories for the control of particularly dangerous infections;

 specialized bacteriological laboratories for the control of certain groups of bacteria: mycobacteria, rickettsia, leptospira, etc.

 Most microbiologicallaboratories works with group III pathogenic pathogensand IV, and the study of pathogens of especially dangerous infections (groups I and II)Only specialized laboratories do this.

Trequirements for work in a microbiological laboratory

 Work with PBA groups III and IV is performed by specialists with higher and secondary specialized education. Employees who have been trained in compliance with the safety requirements for working with biologically active substances are allowed to access it; Subsequent training should be carried out at least once a year. All employees working with PBA must be registered with a dispensary.

 Instruments, equipment and measuring instruments must be certified, technically sound and have a technical passport. Their metrological control and technical certification should be carried out within the established time limits.

From the rules for working in the “dirty area” of the basic laboratory:

The use of special clothing and personal protective equipment is mandatory. Before work, you should check the quality of glassware, pipettes, syringes and other equipment. When pipetting, you must use only rubber bulbs or automatic devices. It is strictly forbidden to pipette the material with your mouth, pour it over the edge (test tubes, flasks), and also leave the workplace unattended while performing any work with PBA.

It is prohibited to smoke, drink water, store outerwear, hats, shoes, or food products in the dirty area. Children and pets must not be brought into the zone premises:

After completion of work, all objects containing pathogenic biological agents must be removed to storage (refrigerators, thermostats, cabinets) with mandatory disinfection of tables.

The used pipettes are completely immersed (vertically) in the disinfectant solution, avoiding the formation of bubbles in the channels. Residues of PBA, used utensils and equipment are collected in closed containers and transferred to the autoclave.

It is strictly prohibited to discharge waste containing PBA into the sewer system without prior disinfection. After finishing work with pathogenic pathogens and infected animals, as well as after leaving the laboratory, you should thoroughly wash your hands.

Lecture No. 2.

Topic: “Morphology of bacteria”

1. Morphology of bacteria.
2. The structure of a bacterial cell.

1 Morphology of bacteria.

According to morphology, all bacteria are divided into 3 groups:

Globular (cocci)

Rod-shaped (rods)

Globular bacteria (cocci)

They have a spherical shape, dimensions 0.5-1 microns, motionless. Based on their relative positions they are divided into 6 morphological groups:

1. Micrococci - singly located cocci (for example, the causative agents of brucellosis)
2. Diplococci are cocci arranged in pairs (the causative agents of gonorrhea, meningococcal infection, pneumonia).
3. Streptococci are located in a chain (for example, causative agents of purulent-inflammatory diseases of the skin, subcutaneous tissue and internal organs).
4. Staphylococci - arranged in a cluster, like bunches of grapes (these are also pathogens
5. Tetracocci - arranged in 4 cells, non-pathogenic for humans.
6. Sarcines - arranged in 8-16 cells, in bales, non-pathogenic.

This mutual arrangement of cocci is associated with the peculiarities of their division.

Rod-shaped bacteria.

They have a cylindrical shape, 1-6 microns in size, there are movable and immobile. Their ends can be rounded, chopped off, pointed, thickened, etc. Among them there are spore-formers.

Rod-shaped bacteria

Spore-forming Non-spore-forming

Aerobes Anaerobes

Clostridia bacilli

The diameter of spores in clostridia exceeds the diameter of the cell, unlike bacilli.

According to the relative position, the sticks can be arranged singly, in pairs, in a chain, at an angle to each other, etc.

Twisted bacteria.

They have a spiral shape. Based on the number of curls they are divided into:

1. Strongly convoluted - now they are classified as spirochetes.
2. Weakly convoluted - spirilla.
3. Vibrios are comma-shaped and are the causative agents of cholera.

2 .Structure of a bacterial cell.

A bacterial cell has basic (all bacteria have) and additional (not all bacteria have) structures.

The main structures include:

1. 3-layer cell membrane (mucosal layer, cell wall, cytoplasmic membrane).
2. Cytoplasm.
3. Nuclear matter.
4. Ribosomes.
5. Inclusions.

Additional structures include:

1. Controversy.
2. Flagella.
3. Villi.
4. Capsules.

Let's consider the structure and functions of cellular structures.

Basic structures of a bacterial cell.

Slime layer.- all bacteria are covered with a layer of mucus, which protects them from the action of phagocytes.

Cell wall- this is the frame of the cell. Its strength depends on the content of the glycoprotein substance. If there is a lot of glycoprotein in the cell wall, then it is thick, and when stained with Gram stain, the bacteria turn blue-violet and are called Gram-positive. If there is little glycoprotein in the cell wall, then it is thin, and when stained with Gram stain, the bacteria stain pink-red and are called Gram-negative. The cell wall performs the following functions:

1. Maintains cell shape.
2. Maintains osmotic pressure in the cell
3. Provides selective cell permeability.

Bacteria with a partially or completely destroyed cell wall are not viable. But sometimes, when treated incorrectly with antibiotics, special forms of microorganisms are formed - L-forms. These are microbes with a partially or completely destroyed cell wall, but retaining viability. After cessation of antibiotic therapy, L-forms restore their cell wall, which is the cause of chronicity and relapse of the disease.

Cytoplasmic membrane - very thin, adjacent directly to the cytoplasm, it contains many enzymes. Protrusions of the cytoplasmic membrane into the cytoplasm are called mesosomes and are involved in cell division.

1. Participates in metabolism
2. Participates in bacterial respiration.
3. Participates in cell division.

Cytoplasm- this is the internal contents of the cell, consisting of organic, inorganic substances and water. Functions: this is the environment in which all the vital processes of the bacterial cell take place.

Nuclear matter (nucleoid) - dispersed throughout the cytoplasm and does not have its own membrane. Consists of a double strand of DNA coiled into a ring. Functions: storage of hereditary information.

Ribosomes- bacteria have many ribosomes distributed throughout the cytoplasm. Functions: protein synthesis.

Inclusions- these are grains of fat, starch, volutin, glycogen. Functions: supply of nutrients.

Additional structures of a bacterial cell.

Disputes- are formed when bacteria enter unfavorable environmental conditions. They represent a compacted area of ​​cytoplasm with nuclear substance and their own dense membrane (i.e., it is like a cell within a cell). The spore contains little water, but a lot of calcium salts and fats, so it is very stable in the external environment. Spores are not killed by boiling or under the influence of disinfectants. They are destroyed only at temperatures above 120 degrees (in an autoclave and dry-heat oven). When exposed to favorable conditions, the spore germinates into a vegetative form and the microbe begins to grow and multiply. In a bacterial cell, spores can be located centrally, terminally or subterminally.

Functions: protection from adverse environmental conditions.

Flagella-- They extend from the basal body, located in the cytoplasm, to the surface of the bacterial cell. Composed of the protein flagellin. Based on the number of flagella, bacteria are divided into:

1. Monotrichs have 1 flagellum.
2. Peritrichous - many flagella over the entire surface.
3. Amphitrichy - a bundle of flagella from 2 ends.
4. Lophotrichous - a bundle of flagella at one end.

Functions are the organs of movement of the bacterial cell.

Cilia (pili, villi, fimbriae). – located over the entire surface bacterial cells, thin, composed of the protein pilin.

1. They ensure adhesion of bacteria to the cells of the macroorganism.
2. Through pili, hereditary information can be transferred from cell to cell.

Capsule- this is a thickened mucous layer.

Functions: provide protection of bacteria from the action of phagocytes of the macroorganism.

Lecture No.3.

Topic: “Morphology of microbes (continued)”

Plan.

1. General characteristics of the main classes of microorganisms from the kingdom of prokaryotes (spirochetes, rickettsia, chlamydia, mycoplasmas, actinomycetes).
2. General characteristics of mushrooms.
3. General characteristics of viruses.

1. General characteristics of the main classes of microorganisms from the kingdom of prokaryotes.

Spirochetes.

1. Borrelia - have 4-6 large uneven curls, are the causative agents of relapsing fever;
2. Treponemas - have 8-12 small uniform curls, are the causative agents of syphilis;
3. Leptospira - have 12-16 small uniform curls and their ends are bent in the form of hooks.

Rickettsia.

Rickettsiae are the causative agents of typhus, Q fever and other rickettsiochs.

Chlamydia.

1. elementary bodies (EB) - small, located in the intercellular space, not capable of division.

2. reticular bodies (RT) - are formed when chlamydia penetrates the sensitive cell of the host. They increase in size and begin to divide. Then RTs are transformed back into ETs, but of a new generation. A microcolony of chlamydia is formed, as a result of which the host cell dies and many newly formed EBs enter the intercellular space, which infect new cells. The intracellular development cycle of chlamydia lasts 48-72 hours.

Chlamydia is the causative agent of the following diseases:

Urogenital chlamydia

Trachoma

Psittacosis

Lymphogranuloma venereum.

Mycoplasmas.

Mycoplasmas are causative agents of the following diseases:

Urogenital mycoplasmosis

Mycoplasma pneumonia.

Actinomycetes.

Translated, it means radiant mushrooms, i.e. Actinomycetes were previously classified as fungi. But now it has been proven that they do not have a formed core. Actinomycetes occur in 2 forms:

In the form of long branching cells resembling mycelium;

In the form of large gram-positive rods.

Among the actinomycetes there are pathogenic ones, which cause actinomycosis, nocardiosis, and non-pathogenic ones - they are used to obtain the antibiotic streptomycin.

Mushrooms.

Fungi are lower plants that do not have chlorophyll. Currently, there are more than 90 thousand varieties, 500 of them are pathogenic for humans. Fungi belong to the kingdom of eukaryotes, i.e. have a formed core, division - Eu Mycota.

Mushrooms are characterized by a general type of structure. All fungi have a cell wall with a unique chemical composition - it includes cellulose- and chitin-like substances. Found in 2 forms:

A) yeast - These are large round cells, Gram-positive.

Fungi often reproduce using spores. The formation of disputes occurs in 3 ways:

a) vegetatively - on any part of the mycelium

b) asexually - in special reproductive organs - sporophores, which form endospores, and conidiophores, which form exospores

c) sexually - in special organs after the fusion of 2 cells.

Fungi are the causative agents of the following diseases.

1. Dermatomycosis (hair damage - trichophytosis or ringworm, damage to the skin of the feet, nails (onychomycosis), scab (favus), microsporia - damage to hair, skin, inguinal epidermophytosis). Dermatomycoses are the most common infectious diseases - in Russia, 80% of the population suffers from one form or another of mycoses.

2. Blastomycosis - candidiasis or thrush, as well as pityriasis versicolor, piedra, terrulosis, North and South American blastomycosis, cryptococcosis.

3. Mold mycoses - the pathogens are saprophytes, the development of the disease occurs only in severe immunodeficiencies and is accompanied by damage to the lungs, skin, oral cavity, etc.

4. Deep mycoses - affect the macrophage system. They are not transmitted from person to person. The main route of transmission is airborne, by inhaling spores. Diseases caused by these pathogens: coccidioidosis, histoplasmosis, etc. All these diseases are characterized by damage not only to the lungs, but also to many organs.

Viruses

Lecture No. 4

on the topic: “Physiology of microbes.”

1. Metabolism of microbial cells.
2. Chemical composition.
3. Nutrition of microbes.
4. Microbial enzymes.
5. Respiration of microbes.
6. Pigment formation.
7. Glow and aroma formation.
8. Growth and reproduction of microbes.

1 . Physiology studies the vital functions of microorganisms: nutrition, respiration, growth and reproduction. Physiological functions are based on continuous metabolism (metabolism).

The essence of metabolism consists of two opposing and at the same time interconnected processes: assimilation (anabolism) and dissimilation (catabolism).

During the assimilation process, nutrients are absorbed and used for the synthesis of cellular structures. During dissimilation processes, nutrients are decomposed and oxidized, releasing the energy necessary for the life of the microbial cell. All processes of synthesis and breakdown of nutrients are carried out with the participation of enzymes.

A feature of microorganisms is intensive metabolism. In one day, under favorable conditions, one microbial cell can process an amount of nutrients that is 30-40 times its mass.

2. CHEMICAL COMPOSITION OF BACTERIA

To understand metabolic processes, it is necessary to know the chemical composition of microorganisms. Microorganisms contain the same chemicals as the cells of all living organisms, i.e. inorganic and organic substances.

Inorganic substances:

The most important elements are organogens (carbon, hydrogen, oxygen, nitrogen), which are used to build complex organic substances: proteins, carbohydrates and lipids.

Quantitatively, the most significant component of a cell is water, which is 75-85%; the share of dry matter, which consists of organic (proteins, nucleic acids, carbohydrates, lipids) and mineral compounds, accounts for 15-25%. The importance of water in the life of a cell is great. All substances enter the cell with water, and metabolic products are removed with it. Water in a microbial cell is in a free state as an independent compound, but most of it is associated with various chemical components of the cell (proteins, carbohydrates, lipids) and is part of cellular structures.

Free water takes part in chemical reactions occurring in the cell. The content of free water in a cell can vary depending on environmental conditions, the physiological state of the cell, and its age. Thus, spore forms of bacteria have significantly less water than vegetative cells. The largest amount of water is observed in capsular bacteria.

Minerals - phosphorus, sodium, potassium, magnesium, sulfur, iron, chlorine and others - on average account for 2-14% of dry matter.

Phosphorus is part of nucleic acids, phospholipids, many enzymes, as well as ATP (adenosine triphosphoric acid), which is an energy accumulator in the cell.

Sodium participates in maintaining osmotic pressure in the cell.

Iron found in respiratory enzymes.

Magnesium is part of magnesium ribonucleate, which is localized on the surface of gram-positive bacteria.

For the development of microorganisms it is necessary micro elements contained in the cell in very small quantities. These include cobalt, manganese, copper, chromium, zinc, molybdenum and many others. Trace elements participate in the synthesis of certain enzymes and activate them.

Organic substances.

Squirrels (50-80% dry matter) determine the most important biological properties of microorganisms. These are simple proteins - proteins and complex ones - proteids. Nucleoproteins - the combination of proteins with nucleic acids (DNA and RNA) - are of great importance in the life of a cell. In addition to nucleoproteins, the microbial cell contains small amounts of lipoproteins, glycoproteins, and chromoproteins.

Proteins are distributed in the cytoplasm, nucleoid, they are part of the structure of the cell wall. Proteins include enzymes and many toxins (poisons of microorganisms).

Nucleic acids in a microbial cell they perform the same functions as in cells of animal origin. DNA is contained in the nucleus (nucleoid) and determines the genetic properties of microorganisms. RNA takes part in the biosynthesis of cellular proteins and is found in the nucleus and cytoplasm. The total amount of nucleic acids ranges from 10 to 30% of the dry matter of a microbial cell and depends on its type and age.

Carbohydrates (12-18% dry matter) are used by the microbial cell as a source of energy and carbon. Many structural components of the cell (cell membrane, capsule, and others) consist of them. Carbohydrates are also part of teichoic acid, which is characteristic of gram-positive bacteria.

Microbial cells contain simple (mono- and disaccharides) and high molecular weight (polysaccharides) carbohydrates.

Lipids (0.2-40% dry matter) are necessary components of the cytoplasmic membrane and cell wall, they are involved in energy metabolism. In some microbial cells, lipids act as storage substances.

Lipids consist mainly of neutral fats, fatty acids, and phospholipids. Their total number depends on the age and type of microorganism. For example, in Mycobacterium tuberculosis the amount of lipids reaches 40%, which makes these bacteria resistant to environmental factors.

3. NUTRITION OF BACTERIA

All microorganisms require nutrients to carry out the processes of nutrition, respiration, and reproduction.

Microorganisms use...

INTRODUCTION

SUBJECT AND TASKS OF MEDICAL MICROBIOLOGY

HISTORY OF THE DEVELOPMENT OF MEDICAL MICROBIOLOGY

SYSTEMATICS AND CLASSIFICATION OF MICROORGANISMS

Basics of bacterial morphology

BACTERIA

INTRODUCTION

Our planet is inhabited by a huge number of living beings. Microorganisms are the most ancient form of life on Earth; they appeared 3-4 billion years ago. They can be found in soil, dust, water, air, on the surfaces of animals and plants, inside organisms, and even in hot springs and in space. All living organisms inhabiting our planet belong to the macro- or microworld.

The macrocosm includes organisms visible to the naked eye:

mammals

reptiles

birds, fish, etc.

To the microcosm - representatives of living nature that can be observed using a microscope:

bacteria

protozoa

From a medical point of view, all microbes can be divided into 3 groups:

Ø Bacteria and fungi destroy organic matter and participate in the cycle of substances in nature.

Ø By decomposing organic substances, microorganisms cause food spoilage.

Ø Some microorganisms, as a result of their vital activity, destroy human structures, causing enormous damage.

Ø Humans use bacteria to purify wastewater.

Ø With the help of microorganisms, a person obtains many irreplaceable products (bread and cheese, wine and kumiss, linen yarn).

Ø Some microorganisms cause infectious diseases in humans.

Ø Many symbiont bacteria live in the intestines of humans and other animals, which bring great benefits to the body.

Ø Bacteria living inside the body produce additional heat.

Ø Man forced microbes to produce bacterial fertilizers, antibiotics, vitamins, and plant protection drugs. This technical use of microorganisms is called biotechnology.

Ø Many protein biological substances that are valuable for medicine are obtained by genetic engineering.

SUBJECT AND TASKS OF MEDICAL MICROBIOLOGY

Microbiology (Greek micros - small, Lat bios - life, logos - teaching) is a science whose subject of study is microscopic creatures called microorganisms, or microbes, their biological characteristics, taxonomy, ecology, relationships with other organisms inhabiting our planet , - animals, plants and humans. Medical microbiology and immunology are closely related to all medical disciplines (infectology, therapy, pediatrics, surgery, phthisiology, hygiene, pharmacology, etc.). The role of microbiology, virology and immunology in solving many health problems has increased significantly.

The goal of medical microbiology is an in-depth study of the structure and most important biological properties of pathogenic microbes, their relationship with the human body in certain conditions of the natural and social environment, improvement of microbiological diagnostic methods, development of new, more effective therapeutic and preventive drugs, solution of such an important problem as the elimination and prevention of infectious diseases. Microbiology studies the diverse world of microbes. In its development, it was divided into several independent disciplines. First of all, it can be divided into general and specific microbiology.

Depending on the tasks to be solved, it is divided into:

microbiology bacterium cell morphology

HISTORY OF THE DEVELOPMENT OF MEDICAL MICROBIOLOGY

Medical microbiology developed from the study of infectious diseases.

The history of the development of medical microbiology as an independent scientific discipline has several stages, determined not so much by time periods as by the level of development of science and technology.

The heuristic stage is a period of guesswork and random discoveries. Ancient thinkers and doctors already guessed about the existence of microbes. “The Father of Medicine” Hippocrates believed that some human diseases are caused by some invisible particles, which he called myiases. They began to guess about the living nature of miasma much later. The Roman poet Verro already definitely considered miasma to be living beings. The mid-century Italian physician Girolamo Fracastoro wrote that diseases are transmitted from person to person by “living contagion.” He created the doctrine of living “contagion” - “the smallest particles inaccessible to our senses”, which, penetrating into the human body, cause disease.

The greatest discovery of the heuristic period in medical microbiology was made at the end of the 18th century. E. Jenner, who proposed vaccination against smallpox by applying the contents of pockmarks (pustules) from sick cows to human skin. The cowpox virus contained in the pustules protected a person from contracting smallpox. The role of microbes in pathology had not yet been proven, the theory of protective vaccinations had not yet been developed, but microbiology began to really help people.

The morphological stage of microbiology began in the 17th century, when the Dutch naturalist A. Leeuwenhoek first saw microbes found in water, herbal infusions, food products, the oral cavity, intestines, etc. For his observations, he used biconvex lenses (magnifying glasses) prepared by himself. They gave an increase of 160 - 200 times. A. Leeuwenhoek called the microbes he saw insignificant “little animals” and described them in detail in letters to the British Royal Scientific Society. all his descriptions of the forms of microbes (spherical, rod-shaped, convoluted, etc.) were so accurate that they have retained their meaning to this day.

He created the prototype of a microscope as a system of two lenses (objective and eyepiece) in 1590. Dutchman Z. Jansen. In subsequent years, this device was improved many times. As a result, in the middle of the 19th century a microscope appeared, which in terms of technical capabilities was not inferior to modern light microscopes. He could magnify objects in question 1000 times. The creation of microscopes stimulated the development of microbiology. The period of “microbe hunters” began.

The causative agents of human hair and skin diseases were the first to be discovered: scab (Schönlein), ringworm (Grubi), pityriasis versicolor (Eichstedt) and thrush (Lagenbeck, Grubi). This is how the science of pathogenic fungi - mycology - was born.

The development of microbiology accelerated after R. Koch developed solid nutrient media for obtaining pure cultures of microorganisms at the end of the 19th century, and also proposed the use of dyes to study the morphology of microbial cells.

Various microbiological techniques developed by R. Koch made it possible to study the causative agents of almost all infectious diseases. R. Koch isolated a pure culture of the causative agent of anthrax, tuberculosis (Koch's bacillus) and cholera (Koch's comma).

Among all the “microbe hunters,” the most famous was the French scientist L. Pasteur. He proved the pathological role of microbes in puerperal fever, abscesses and osteomyelitis.

In subsequent years, T. Escherich discovered E. coli, E. Roux - diphtheria bacillus, D. Salmon - pathogens of intestinal infections. New discoveries followed. K. Shiga described the causative agents of dysentery and whooping cough, G. Hansen - leprosy, S. Kitazato - tetanus and plague, and F. Schaudin and E. Hoffman - syphilis.

The most important event in microbiology was the discovery of toxic substances (toxins) secreted by microbes. This was done by L. Pasteur's student - E. Roux, who proved that the main symptoms and severity of diphtheria are caused by the toxin secreted by the diphtheria bacillus. They proposed a method for treating diphtheria using specific blood serum proteins (antibodies) that neutralize the microbial toxin. All of these “microbe hunters” laid the foundations of medical microbiology.

At the end of the 19th century, it was discovered that human diseases can be caused not only by bacteria, but also by protozoa. Russian scientists F.A. Lesh and P.F. Borovsky discovered the causative agents of amoebic dysentery and cutaneous leishmaniasis. Subsequently, the pathogenic role of malarial plasmodium, trichomonas, toxoplasma, balantia and other protozoa was proven. A new direction in medical microbiology was born - protozoology.

Russian scientist I.I. Mechnikov, who worked at the L. Pasteur Institute, was the first to study the world of the body’s own microflora and other microbes surrounding humans. He was the first to point out the great importance of microflora for human life in normal conditions and in pathology. The pathogenic properties of autoflora and environmental microbes appear only when human health deteriorates (opportunistic microbes). Thus, I.I. Mechnikov is the founder of a new branch of microbiology - environmental microbiology.

The morphological period of development of microbiology is not over, as scientists are making more and more new discoveries. In total, about 4,000 species of bacteria have been isolated and studied to date.

The development of microbiological technology, the creation of fine-porous filters with a certain pore size, and the use of cell culture methods made it possible to discover viruses. The period of “microbe hunters” gave way to the period of “virus hunters.” The first of them was the Russian scientist D.I. Ivanovsky, who isolated the tobacco mosaic virus in its pure form (1892). Following him, F. Leffler and P. Frosch discovered the foot-and-mouth disease virus, which infects animals, T. Smith - the yellow fever virus, which causes liver damage in humans, F. Darelle - a bacteriophage (a virus that infects bacteria), V. Smith and co-authors - a virus flu, L.A. Zilber - encephalitis virus and oncogenic viruses. A new science has emerged - virology.

The development of virology was facilitated by the invention in the 30s of the twentieth century of the electron microscope, which uses a source of electrons focused by electrostatic lenses as an illuminator. An electron microscope magnifies the image of an object 10,000 times. Its creation made it possible to see “portraits” of viruses.

The study of pathogenic viruses continues. In 1982, L. Montagnier and R. Galo discovered the human immunodeficiency virus (HIV/AIDS). In 2003, Chinese scientists described the virus that causes acute respiratory syndrome (SARS) - atypical pneumonia.

In 1963, the American scientist K. Gaidushek proved the existence of a fundamentally new infectious principle called a prion. Unlike all other microbes, prions do not contain nucleic acids and are proteins with low molecular weight (infectious protein molecules). They affect the cells of the central nervous system, causing their rupture and sponge-like degeneration, which naturally ends in the death of the body. Diseases caused by prions began to be called “slow infections”, since between infection and death of the organism passed from 5 to 20 years. To date, no treatment for these diseases has been developed.

The discovery of pathogens was accompanied by the study of their biological properties. The morphological period of development of microbiology was followed by the PHYSIOLOGICAL. During this period, the processes of metabolism and respiration in microbes, their enzymatic activity, reproduction and growth on nutrient media were studied. The physiological period of development of microbiology is associated with the name of L. Pasteur. He discovered the enzymatic nature of fermentation caused by the activity of microbes, laid the foundations of industrial microbiology, and founded the principles of sterilization of nutrient media. The study of the vital functions of microbes has led to the emergence of antibacterial drugs that can kill microbes in the body or prevent their reproduction (sulfonamides and antibiotics). P. Ehrlich, who synthesized sulfonamide - streptocide, can be considered the founders of chemotherapy. The first antibiotic penicillin was isolated in a chemically pure form by the English scientist A. Fleming and the domestic microbiologist Z. V. Ermolyeva. The list of antibacterial drugs is expanding every year. Currently, their number is in the hundreds. Drugs with antiviral activity (interferon) were obtained.

With the names of L. Pasteur, I.I. Mechnikov and P. Ehrlich are associated with the immunological stage of the development of microbiology. Medical practice has included preventive vaccines prepared from microbes against many infectious diseases, as well as therapeutic serums containing specific antibodies against microbial toxins.

In the twentieth century, the stage of development of molecular genetic microbiology and immunology began. At this time, they studied the basics of the molecular structure of microbes, antibodies, the genetic apparatus of cells and, finally, the human genetic code, which provides, in particular, the body’s immune response.

SYSTEMATICS AND CLASSIFICATION OF MICROORGANISMS

M/o are organisms invisible to the naked eye due to their small size.

The basic category (taxon) of biological classification, reflecting a certain stage of evolution of a separate population of organisms - species. A species is an evolutionarily established set of individuals that have a single genotype, which under standard conditions is manifested by similar morphological, biochemical and other characteristics. Principles of taxonomy and nomenclature of microorganisms

Living organisms (microorganisms) M/o belong to 3 kingdoms:

Prokaryotes PROCARIOTAE:

Eubacteria

Gracilicutes (thin cell wall)

Firmicutes (thick cell wall)

Spirochetes, rickettsia, chlamydia, mycoplasmas, actinomycetes. Archaebacteria

Mendocutes

Eukaryotes EUCARIOTAE: Animals Plants Fungi Protozoa Non-cellular life forms VIRA: Viruses Prions Plasmids

For microorganisms, the following categories (taxa) of the taxonomic hierarchy are accepted (in ascending order): Species - Genus - Family - Order - Class - Division - Kingdom.

Species names are binomial (binary), that is, they are denoted by two words. The first word denotes the Genus and is written with a capital letter, the second word denotes the Species and is written with a lowercase letter.

Scheme for the formation of the binomial name of microorganisms.

Examples of constructing a binomial name for bacteria.

BASICS OF BACTERIAL MORPHOLOGY

Specialized terms:

Strain is a culture of microorganisms isolated from a specific specific source (organism or environmental object).

Shape of bacteria. Size of bacteria.

The structure of a bacterial cell.

Characteristics of some groups of bacteria.

FORM OF BACTERIA. BACTERIA SIZE

Certain types of bacteria are characterized by certain shapes and sizes with sufficient constancy.

There are three main forms of bacteria - spherical, rod-shaped and convoluted.

Globular bacteria, or cocci

The shape is spherical or oval.

Micrococci are individually located cells.

Diplococci are found in pairs.

Streptococci are round or elongated cells that form a chain.

Sarcines - arranged in the form of “packets” of 8 or more cocci. Staphylococci are cocci arranged in the form of a bunch of grapes as a result of division in different planes.

Rice. 1. Globular bacteria (enterococci). Electron microphotography (EM).

Rod-shaped bacteria. The shape is rod-shaped, the ends of the cell can be pointed, rounded, chopped off, split, or expanded. Rods can be regular or irregular in shape, including branching, for example in actinomycetes.

Based on the nature of the arrangement of cells in smears, the following are distinguished:

Monobacteria - located in separate cells.

Diplobacteria - arranged in two cells.

Streptobacteria - after division they form chains of cells.

Rod-shaped bacteria can form spores: bacilli and clostridia.

Rice. 2. Rod-shaped bacteria (Escherichia coli). EM.

Twisted bacteria

Shape - a curved body in one or more revolutions.

Vibrios - the curvature of the body does not exceed one revolution.

Spirochetes are bends of the body in one or several turns.

Rice. 3. Convoluted bacteria (Vibrio cholerae). EM.

Bacteria size

Microorganisms are measured in micrometers and nanometers.

The average size of bacteria is 2 - 3 x 0.3 - 0.8 microns.

Shape and size are an important diagnostic sign.

The ability of bacteria to change their shape and size is called polymorphism.

BACTERIA

STRUCTURE OF A BACTERIAL CELL

The structure of bacteria.

The body of the bacterium consists of cytoplasm (with various inclusions) and a cytoplasmic membrane, surrounded by a cell wall.

Cytoplasm occupies the bulk of the bacterial cell. The most important component of the cytoplasm is nucleotide, which is considered the equivalent of the nucleus and is located in the central zone of the bacterium. In addition to the nucleotide, the cytoplasm contains plasmids, which are factors of heredity (there can be from 1 to 200 of them).

The cytoplasmic membrane limits the cytoplasm (participates in the transport of nutrients).

Between the cell wall and the cytoplasmic membrane there is a space - the periplasm, containing enzymes.

The cell wall is a strong structure that gives the bacterium its specific shape. Based on the type of cell wall structure, bacteria are divided into gram-positive with a thick wall and gram-negative with a thin cell wall.

The main component of the cell wall of gram-positive bacteria is peptidoglucan, which is capable of retaining gentian violet dye in complex with iodine (blue-violet color) when the preparation is treated with alcohol.

During their life, bacterial cells form protective organelles - capsules and spores.

Capsule is the outer thickened mucous layer adjacent to the cell wall. This is a protective organ that appears in some bacteria when they enter the human or animal body. The capsule protects the tissue from the body’s protective factors (prevents the capture of bacteria by phagocytes).

A spore is a form of gram-positive bacteria formed under unfavorable conditions of cell existence (drying, nutrient deficiency, temperature changes, etc.). The formation of spores contributes to the preservation of the species and has nothing to do with the proliferation of bacteria.

Spore-forming aerobic bacteria are called bacilli, and anaerobic bacteria are called clostridia.

Spores differ in shape, size and location in the cell. They can be located:

Flagella ensure the mobility of the microbe; only rod-shaped bacteria have them; they originate from the cytoplasmic membrane.

Based on the number of flagella there are:

Monotrich (one in Vibrio cholerae);

Peritrich (up to hundreds in E. coli)

Amphitrichy - one or several flagella at opposite ends of the microbial cell (spirilla)

Lophotrichous - have a bundle of flagella at one end of the cell.

Villi, or pili, are thread-like structures, shorter than flagella. They extend from the surface of the bacterium, consist of the protein pilin and are responsible for the adhesion of the microbe to the affected cell. Among the pili, sex pili are distinguished, inherent in “male” donor cells containing transmissible plasmids (F, R, Col). A bacterial cell consists of a cell wall, a cytoplasmic membrane, cytoplasm with inclusions and the so-called nucleoid. There are additional structures: capsule, microcapsule, flagella, pili. Some bacteria are capable of forming spores under unfavorable conditions.

Rice. 4. Structure of a bacterial cell (diagram). Сapsule - capsule; Cell wall - cell wall; Cytoplasmic membrane - cytoplasmic membrane; Mesosome - mesosome; Flagellum - flagellum; Pili - drank; Cytoplasma - cytoplasm; Nucleoid - nucleoid; Ribosomes - ribosomes; Granular inclusion - inclusions.

Rice. 5. Identify the shaped elements of a bacterial cell.

Gram-positive bacteria have a thick (multilayered) cell wall.

Gram stained purple.

Gram-negative bacteria have a thin cell wall covered on the outside by a triple lipid-containing layer (outer membrane). They stain red with Gram staining.

Rice. 6. The structure of the cell wall of gram-positive (A) and gram-negative (B) bacteria (diagram).

In gram-positive bacteria (A), the main layer - peptidoglycan - is multilayered and permeated with teichoic acids (thick cell wall); Gram-negative bacteria (B) have a thin peptidoglycan and above it is an outer membrane containing lipids (thin cell wall).

Tinctorial properties - the susceptibility of microorganisms to various dyes. Forms - bacteria completely devoid of a cell wall and capable of reproducing.

Disputes and sporulation

Bacterial spores are a peculiar form of resting bacteria, a form of preserving hereditary information in unfavorable environmental conditions and are not a method of reproduction, like fungi.

The process of sporulation: sporogenic zone - prospore - spore.

Under favorable conditions, spores germinate in 4-5 hours. They form spores within 18-20 hours.

Rice. 7. Spore inside a bacterial cell (EM).

Rice. 8. Anthrax bacillus spores (light optical microscopy, SM).

Lecture No. 2.

SYSTEMATICS AND NOMENCLATURE.

4. Adaptability.

3 domains(or " empires»): « Bacteria », « Archaea " And " Eukarya »:

domain " Bacteria» eubacteria );

domain " Archaea» archaebacteria ;

domain " Eukarya» Eukarya » includes: kingdom Fungi (mushrooms); animal kingdom Animalia Protozoa ); plant kingdom Plantae .

taxonomy [from Greek taxi – location, order, + nomos taxa

protista [from Greek protistos eukaryotes [from Greek eu- – good, solid + karyon prokaryotes [from Greek pro- previous + karyon

Systematics of microorganisms.

Natural (phylogenetic) taxonomy of microorganisms has the ultimate goal of uniting related forms related by common origin and establishing a hierarchical subordination of individual groups.

Until now, there are no unified principles and approaches to combining (or dividing) them into various taxonomic units, although they are trying to use the similarity of genomes as a generally accepted criterion. Many microorganisms have the same morphological characteristics, but differ in the structure of their genomes; the relationships between them are often unclear, and the evolution of many is simply unknown. Moreover, the cornerstone concept for each classification "view" for bacteria still does not have a clear definition, and in some cases the true relationship between bacteria may be controversial, since it only reflects a common origin from one distant ancestor. Such a simplified criterion as size, used at the dawn of microbiology, is currently absolutely unacceptable. In addition, microorganisms differ significantly in their architecture, biosynthetic systems, and organization of the genetic apparatus. They are divided into groups to demonstrate the degree of similarity and the assumed evolutionary relationship. The basic feature used to classify microorganisms is the type of cellular organization.

Artificial (key) taxonomy of microorganisms, uniting organisms into groups based on the similarity of their most important properties.

These characteristics are used to determine and identify microorganisms. From the standpoint of medical microbiology, microorganisms are usually divided according to the effect they have on the human body: pathogenic, opportunistic and non-pathogenic. Despite the obvious importance of this utilitarian approach, their taxonomy is still based on principles common to all life forms. For
To facilitate diagnosis and decision-making regarding treatment and prognosis of the disease, identification keys have been proposed. Microorganisms grouped in this manner are not always phylogenetically related, but are listed together because they have several easily identifiable similar properties. A variety of accessible and rapid tests have been developed that allow, at least in general terms, the identification of microorganisms isolated from a patient. With regard to bacteria, the most widespread are the approaches to systematization proposed by the American bacteriologist David Bergey, which take into account one or more of the most characteristic features. "Burgee's Bacteria Determinant" - a typical example of artificial taxonomy. According to his principles, easily identified properties are
basis for combining bacteria into large groups.

Genus and above.

The names of taxa with genus rank and higher are uninominal (unitary), that is, denoted by one word, for example Herpesviridae (herpesvirus family).

Species names are binomial (binary), that is, they are denoted by two words - the name of the genus and the species. For example, Escherichia coli (Escherichia coli). The second word of a binary species name, taken alone, has no status in nomenclature and cannot be used to scientifically designate a microorganism. The exception is viruses whose species names are not binary, that is, they include only the species name (for example, rabies virus).

Infraspecific taxa.

The taxonomy of bacteria also includes intraspecific taxa, the names of which do not obey the rules of the International Code of Nomenclature of Bacteria.

Subspecies.

The names of the subspecies are trinominal (trinary); the word subspecies is used to denote them ( subspecies ) after the species name, for example Klebsiellapneumoniaesubsp.ozenae (ozena wand, where ozenae – name of the subspecies).

Option.

Various mechanisms of bacterial variability lead to a certain instability of characteristics, the totality of which determines a particular species. Therefore, in the taxonomy of bacteria the concept is widely used "option" . There are morphological, biological, biochemical, serological and many other options. In medical bacteriology, serological variants (serovars), variants resistant to antibiotics (resistancevars), bacteriophages (phagevars), as well as variants that differ in biochemical (chemovars), biological or cultural characteristics (biovars) are usually distinguished.

Strain and clone.

In microbiology, specialized terms are also used - “ strain " And " clone ».

Strain[from German stammen – occur] is a culture of microorganisms isolated from a specific source (an organism or an environmental object).

Clone[from Greek clone – layering] is a culture of microorganisms obtained from one mother cell.

Viroids.

Viroids[from virus and Greek eidos – similarity] – are small circular single-stranded supercoiled RNA molecules (the genome of the hepatitis D virus has a similar organization). Since viroids do not have a protein coat, they do not exhibit pronounced immunogenic properties and therefore cannot be identified by serological methods. Viroids cause diseases in plants.

Prions.

Included in the kingdom Vira as an unnamed taxon.

Prions [from English. proteinaceousinfectious (particle ), protein-like infectious (particle)] – protein infectious agents leading to the development of lethal neurological diseases (spongiform encephalopathies). Prion proteins have been identified as the infectious cause of scrapie in sheep, bovine spongiform encephalopathy (“mad cow disease”), and in humans, kuru, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. Prions are transmitted by inoculation or nutrition not only between individuals of the same biological species, but also between animals of different species, including between animals and humans.

The pathogenesis of prion diseases is associated with a change in the nature of the folding of the polypeptide chain, that is, a change in the conformation of the protein. As a result, conglomerates are formed in the form of rods or ribbons with a size of 25~550 × 11 nm. These prion forms of proteins are resistant to boiling, ultraviolet (UV) irradiation, 70% ethanol and formaldehyde and are preserved in tissues fixed with 10% formaldehyde. Once in a healthy human or animal body, pathological conformers contribute to the gradual deposition of amyloid-like structures, which also include normal proteins. PrP C .

Acid-fast bacteria.

The cell wall of some bacteria contains large amounts of lipids and waxes, making them resistant to subsequent bleaching with acids, alkalis or ethanol after staining (for example, species Mycobacterium or Nocardia ). Such bacteria are called acid-fast and are difficult to stain with Gram (although acid-fast bacteria are considered Gram-positive). The Ziehl-Neelsen method is used to stain them.

Gram or Ziehl-Neelsen staining has diagnostic value for bacteria that have a strong cell wall. They are not suitable for staining mycoplasmas (no cell wall) or spirochetes (cell wall is thin and easily destroyed during staining). To study the latter, various methods of applying contrasting substrates to their surface (for example, silvering) are used.

Mobility.

An important differentiating feature is mobility. In accordance with the method of movement, gliding bacteria are distinguished, moving due to wave-like contractions of the body, and floating bacteria, the movement of which is ensured by flagella or cilia.

Ability to form spores.

To classify some bacteria, their ability to form spores, the size of the spores and their location in the cell are taken into account.

Physiological activity.

Physiological activity is an equally important distinguishing feature. Bacteria are divided according to the method of nutrition, the type of energy production (respiration, fermentation, photosynthesis), in relation to pH, indicating the limits of stability and optimum growth, etc. The most important criterion is the attitude towards oxygen.

Aerobic bacteria use molecular O2 as the final electron acceptor during respiration. Most bacteria possess membrane-bound cytochrome C oxidase, which plays a leading role in the electron transport chain. To identify the enzyme, an oxidase test is used, based on the ability of a colorless substance NN -dimethyl- p -phenylenediamine acquires a crimson color upon reduction.

Anaerobic bacteria do not utilize molecular O2 as the final electron acceptor. Such bacteria obtain energy either through fermentation, where the final electron acceptors are organic compounds, or through anaerobic respiration, using an electron acceptor other than oxygen (for example, NO 3 ¯ , SO 4 2- or Fe 3+).

Optional bacteria can obtain energy either through respiration or fermentation, depending on the presence or absence of oxygen in the environment.

Biochemical properties.

To differentiate bacteria, their ability to ferment carbohydrates, form various products (hydrogen sulfide, indole) or hydrolyze proteins is studied.

Antigenic properties.

The antigenic properties of various bacteria are specific and are associated with the structural features of cellular structures, recognized by special antisera as antigenic determinants. Typing of bacteria by antigenic structure is carried out in an agglutination reaction (RA), mixing a drop of antiserum with a drop of bacterial suspension. With a positive reaction, individual aggregated lumps appear in an initially homogeneous bacterial suspension. The following types of hypertension are distinguished:

genus-specific , detected in all representatives of a particular genus, including individual strains;

species-specific , detected in individual species and strains of microorganisms;

serovar- (strain-) specific , detected in representatives of various subgroups (strains) within a particular species.

Chemical composition.

An important classification feature is the total chemical composition of bacterial cells. The content and composition of sugars, lipids and amino acids in cell walls are usually determined.

Genetic relationship.

For the phylogenetic classification of bacteria, the best and most informative indicator is genetic relatedness. When systematizing bacteria based on genetic relatedness, a number of indicators are taken into account.

The ability to exchange genetic information (for example, in the process of transformation or conjugation), possible only between organisms of the same genus or species.

Composition of DNA bases (guanine-cytosine:adenine-thymine ratio).

Similarity of nucleic acids revealed by hybridization.

Codex of names of mushrooms.

The Code of Fungal Names contains provisions providing for the assignment of separate names to the perfect (sexual, or marsupial) and imperfect (asexual, or conidial) stages. Many fungi have known asexual stages ( anamorphs ) and sexual stages are unknown ( teleomorphs ). Therefore, the code allows the different stages (if any) to be given different names. For example, the sexual forms of the yeast fungus Cryptococcus neoformans serovars A And D systematize how Filobasidiellaneoformansvar. neoformans or how Cryptococcus neoformansvar. neoformans . Teleomorphyserovar IN And WITH- How Filobasidiellaneoformansvar. bacillispora or how Cryptococcus neoformansvar. gatti .

Lecture No. 2.

SYSTEMATICS AND NOMENCLATURE.

Of primary importance, of course, is the question of whether the diversity of forms of existence around us belongs to living or nonliving matter. It was with the development of biology in general and microbiological science in particular, and the discovery of previously unknown forms of life, that some established criteria were put forward that distinguish living matter. These include:

1. The ability to grow and reproduce;

2. Possession of heredity and variability;

3. Susceptibility to evolution (progressive and regressive);

4. Adaptability.

All existing classifications of life forms are extremely diverse and none of them is complete, comprehensive and universally accepted.

According to the new highest level in the classification hierarchy, cellular life forms are distinguished 3 domains(or " empires»): « Bacteria », « Archaea " And " Eukarya »:

domain " Bacteria» - prokaryotes, represented by real bacteria ( eubacteria );

domain " Archaea» - prokaryotes represented archaebacteria ;

domain " Eukarya» - eukaryotes, whose cells have a nucleus with a nuclear envelope and nucleolus, and the cytoplasm consists of highly organized organelles - mitochondria, Golgi apparatus, etc. Domain " Eukarya » includes: kingdom Fungi (mushrooms); animal kingdom Animalia (includes protozoa - subkingdom Protozoa ); plant kingdom Plantae .

The taxonomy of living organisms is one of the most difficult problems in biology. Systematics concentrates all the main achievements of science - the more specific they are, the more accurate the classification. Any classification of living organisms is intended to show the degree of similarity and the expected evolutionary relationship (at the same time, higher categories are capacious and broad, and lower ones are specific and limited). The principles of classification are studied by a special section of taxonomy - taxonomy [from Greek taxi – location, order, + nomos - law]. Within a particular taxonomic category there are taxa - groups of organisms united by certain homogeneous properties.

All existing classifications of life forms are very heterogeneous, none of them is complete, comprehensive and universally accepted. The clear boundaries of the plant world and the animal world collapsed after the discovery of microorganisms.

For the third kingdom of living beings, Ernst Heckel (1866) proposed a collective name protista [from Greek protistos - first]. All of them are distinguished by a simpler cell structure than that of animals and plants. Higher protists (fungi, algae and protozoa) – eukaryotes [from Greek eu- – good, solid + karyon – nucleus] – have a morphologically separate nucleus and divide mitotically, which resembles plant and animal cells. A more simply organized group consists of prokaryotes [from Greek pro- previous + karyon – nucleus] – bacteria and blue-green algae, whose cells do not have a membrane around the nucleus substance. Later, representatives of the microcosm were supplemented by non-cellular life forms - viruses, plasmids, viroids, etc.

Principles of classification of microorganisms.

View – a set of individuals with the same phenotype, producing fertile offspring and living in a certain area.

Methodological development of a lecture lesson

Topic: Classification and basics of morphology of microorganisms

Lecture outline:

1. Classification of microorganisms.

2. Bacteria.

3. The structure of a bacterial cell.

4. Mycoplasmas, spirochetes, rickettsia, actinomycetes.

5. Brief characteristics of viruses

6. Protozoa. Brief description of the main representatives.

Classification of microorganisms

Microorganisms include protozoa, spirochetes, rickettsia, fungi, bacteria, and viruses. Their value is measured in microns (micrometers).

The first attempt to classify microorganisms was made by C. Linnaeus in the 18th century. It was based on morphological characteristics. He divided all microorganisms as follows:

1. Prokaryotes – bacteria and viruses;

2. Eukaryotes – fungi and protozoa.

In addition, he proposed a binary system, which consists of a double name for microorganisms in Latin. For example:

Staphylococcus aureus – Staphylococcus aureus;

Eshtrihia coli - Escherichia coli

Before moving on to the modern classification, let's define some terms:

Eukaryotes– microorganisms that have a formed nucleus and chromosomes.

Prokaryotes- single-celled organisms that do not have a formed nucleus; instead, they have one strand of DNA.

Gram+- these are microorganisms containing an Mg RNA salt in their cell wall, which, when stained, forms a complex with the dye. This complex is not destroyed when exposed to alcohol and the microbes turn purple.

Gram- These are microorganisms that do not have the Mg salt of RNA, the complex is not formed, and the dye is washed off with alcohol. Microbes turn pink.

In 1980, an international classification was adopted, proposed by the American scientist Bergi. He proposed that within a species there are variants that differ from each other.

- morphovariants– differ in morphology;

- biovariants– differ in biological properties;

- chemovariants– differ in enzymatic activity;

- serovars– differ in antigenic structure;

- phage variants– differ in sensitivity to phages.

Also, the Bergey classification is based on the structure of the cell wall, on the basis of which bacteria are divided into four sections:

1. Gracilicutes – with a thin cell wall, Gr- (spirochetes, spirilla, various bacteria, rickettsia)

2. Fermicutes – with a thick cell wall, Gr+ (spherical bacteria, actinomycetes, mycobacteria)

3. Tenericut – without a rigid wall (mycoplasma)

4. Mendosicuta – archibacteria, representatives of ancient life forms, among which there are no pathogens of infectious diseases.