Classification of harmful bacteria. Principles of classification of microorganisms

Determination of their pathogenicity. For example, the likelihood of developing the disease when Staphylococcus aureus is found in the blood is much higher than when Staphylococcus epidermidis is present. Some bacteria (such as Corynebacterium diphtheriae and Vibrio cholerae) cause serious disease and have the ability to spread epidemically. Methods for identifying bacteria are based on their physico-immunological or molecular properties.

Gram stain: the sensitivity of gram-positive and gram-negative to the action of antibiotics differs. Some other microorganisms (eg mycobacteria) require other staining methods to identify them.

Gram stain classification of bacteria

The form: cocci, rods or spirals.

Endospores, their presence and location in the bacterial cell (terminal, subterminal or central).

Relation to oxygen: aerobic microorganisms require oxygen for existence, while anaerobic bacteria are able to survive in an environment with a low content of it or total absence. Facultative anaerobes can live both in the presence of oxygen and without it. Microaerophiles multiply rapidly at a low partial pressure of oxygen, and capnophiles - in an environment with a high content of CO2.

exactingness: Some bacteria require special culture conditions to grow.

Classification of bacteria in relation to oxygen

Essential Enzymes(enzymatic activity): for example, a lack of lactose in the medium indicates the presence of salmonella, and a urease test helps to identify Helicobacter.

Serological reactions arise when antibodies interact with the surface structures of bacteria (some types of Salmonella, Haemophilus, meningococci, etc.).

The sequence of bases in DNA: The key element in the classification of bacteria is the 168-ribosomal DNA. Despite the universality of the above parameters, it should be remembered that they are relative to a certain extent and in practice they sometimes show significant variability (for example, intraspecific differences, interspecific similarities). Thus, some strains of E. coli sometimes cause diseases that are clinically similar to infections caused by Shigella sonnei; and the clinical picture of diseases caused by toxigenic strains of C. diphtheriae differs from that in infections caused by non-toxigenic forms.

Significant bacterial species in medicine

Gram-positive cocci:
- staphylococci (catalase-positive): Staphylococcus aureus, etc.;
- streptococci (catalase-negative): Streptococcus pyogenes, which causes tonsillitis, pharyngitis and rheumatic fever; Streptococcus agalactiae, which causes meningitis and pneumonia in newborns.

Gram-negative cocci: Neisseria meningitidis (the causative agent of meningitis and septicemia) and N. Gonorrhoeae [the causative agent of urethritis (gonorrhea)].

Gram-negative coccobacilli: causative agents of respiratory diseases (genus Haemophilus and Bordetella), as well as zoonoses (genus Brucella and Pasteurella).

Gram-positive bacilli divided into spore-forming and non-spore-forming bacteria. Spore-forming bacteria are divided into aerobic (genus Bacillus, for example, Bacillus anthracis, which causes anthrax) and anaerobic (Clostridium spp., diseases such as gas gangrene, pseudomembranous colitis and botulism are associated with them). Non-spore-forming bacteria include the genera Listeria and Corynebacterium.

Gram negative rods: facultative anaerobes of the Enterobacteria family (opportunistic representatives of the normal microflora of humans and animals, as well as microorganisms often found in environment). The most famous representatives of the group are bacteria of the genera Salmonella, Shigella, Escherichia, Proteus and Yersinia. Recently, antibiotic-resistant strains of the genus Pseudomonas (saprophytes, widespread in the environment) are increasingly acting as causative agents of nosocomial infections. Under certain conditions, Legionella living in the aquatic environment can become pathogenic for humans.

Spiral bacteria:
- small microorganisms of the genus Helicobacter, affecting gastrointestinal tract human and causing gastritis, peptic ulcer stomach and duodenum (in some cases - stomach cancer);
- causative agents of acute diarrhea;
- bacteria of the genus Borrelia that cause epidemic relapsing fever (B. duttoni, B. recurrentis); chronic diseases of the skin, joints and central nervous system; Lyme disease (B. burgdorferi);
- microorganisms of the genus Leptospira, related to zoonoses, causing acute meningitis, accompanied by hepatitis and renal failure;
- the genus Treponema (the causative agent of syphilis T. pallidum).

Rickettsia, Chlamydia and Mycoplasma. The use of artificial nutrient media is possible only for growing bacteria of the genus Mycoplasma, while for the isolation of microorganisms of the genera Rickettsia and Chlamydia, it is necessary to use cell culture or special molecular and serological methods.

bacteria- These are unicellular, chlorophyll-free organisms that reproduce vegetatively by division, less often by lacing, sometimes forming intracellular spores.

The size of bacteria is measured in microns and, with rare exceptions, ranges from 0.06-0.3 to 3-5 μ. A drop of water can easily contain several hundred million bacteria.

The shape of a bacterial cell is quite uniform. Three main forms of bacteria are known: round, rod-shaped and convoluted with numerous and inconspicuous transitions between them. Anton De Bari figuratively compared them with a billiard ball, a pencil and a corkscrew.

Bacteria that have round shape. They differ in size and relative position. Cocci connected in pairs are called diplococci, but connected in the form of a necklace are called streptococci. When dividing, alternating in two mutually perpendicular directions, tetracocci are formed. If the division is correct and repeats in three mutually perpendicular directions, then cell connections are formed in the form of packages - these are the so-called sardines. Dividing in different directions without much regularity, cocci form random clusters resembling a brush of grapes. They are called staphylococci.

Rod-shaped bacteria are somewhat more diverse in their appearance. They can be with truncated or rounded ends, cylindrical, barrel-shaped or lemon-shaped and, as it were, with a constriction in the middle, often ellipsoidal, differing only in their width and length. Sticks can be straight, curved, single, linked in pairs or in a chain, short or strongly elongated. Rod-shaped bacteria, in which the length is twice or more than the width, are called bacilli; if the difference between length and width is small, then they are called bacteria.

Curly-shaped bacteria differ not only in length and thickness, but also in the number and nature of curls. Slightly curved bacteria (the curl does not exceed 1/4 turn of the spiral) are called vibrios, bacteria that have one or more large regular curls are called spirillum. Long and thin bacteria of a convoluted shape with numerous small curls, sometimes with large curvatures of the entire filament, are called spirochetes.

The structure of bacteria

By the simplicity of their organization and their insignificant size, bacteria belong to the most elementary beings and stand on the lowest rungs of life. Despite the tremendous advances in science and technology, not all questions of the structure of bacteria have yet been resolved.

The body of bacteria consists of a shell and protoplasm of ethical content, impregnated with cell sap. The shell of bacteria is thin, colorless, its structure is not distinguishable under a microscope. In order to see it, they resort to artificial methods of processing. The sheath underlies the outer shape of the cell and appears to be a well-known defense against adverse conditions. Freely enveloping the contents of the cell, thanks to its elasticity, it allows the free movement of bacteria, often accompanied by brisk movements of the whole body.

The outer layers of the shell, absorbing water, often swell and form a gelatinous sticky mass, reaching a noticeable size. As the outer layers become mucilaginous, the shell is continuously renewed at the expense of protoplasm. The cooled adhesive shell is called a capsule. The intensity of the formation of mucus and capsules depends on the characteristics of nutrition and can sometimes be very significant. The mucous capsule is formed not only near each cell separately, but also in many cells connected in one colony and enclosed, as it were, in a common capsule. These slimy colonies of bacteria are called zoogles. The formation of capsules is not characteristic of all types of bacteria.

movement of bacteria

The ability to spontaneous movement is inherent only in some groups of bacteria. Bacteria move by means of flagella or cilia. Flagella look like more or less long filaments. They are very delicate, thin, break off easily, and are not visible under a microscope without special staining. Their diameter does not exceed 1/20 of the diameter of the bacterial body.

Mobile forms of bacteria are divided into the following groups:

• monotrichous - there is only one polar flagellum,
• lophotrichous - there is a bundle of flagella at one end of the cell,
• peritrichous flagella are located over the entire surface of the body.

The nature of the location of the flagella on the body of the bacterium determines the nature of its movement - rectilinear or random. The motility of bacteria depends on a number of conditions: temperature, composition of the nutrient medium, products of their vital activity, etc. Motile forms of bacteria are not equipped with flagella at all stages of their development and not under all growth conditions.

sporulation

In the body of many bacteria, at certain periods of their development, round or ellipsoidal formations appear - supports. They usually complete the development cycle of bacteria. The size of the spores compared with the size of the cells that produced them can vary widely.

Supports are not formed in all types of bacteria. They are surrounded by a well-isolated shell, almost impervious to water and are the most stable formations among the entire living world. So, they often withstand boiling for several hours and prolonged exposure to dry steam at temperatures from 120 to 140 °. The spores of many bacilli retain their viability after a long stay at a temperature of -190 ° and even at a temperature of liquid hydrogen (-253 °). They are also resistant to chemical substances- poisons. All this makes it extremely difficult to fight pathogenic spore species of bacteria.

A mature spore can remain viable for decades. Usually, spore germination occurs after a certain dormant period and is associated with the influence of external conditions. The entire process of sporulation occurs within a day or less. After the spore matures, the cell that produced it gradually dies off and the mature spore comes out. During germination, it swells, becomes richer in water, and a seedling comes out of it, dressed in a thin shell.

Reproduction of bacteria

Having reached the state of maturity and growth limit, bacteria begin to multiply by simple division. During division, a septum appears in the middle part of the body of the bacterium, which then splits and separates two new cells. The sequential arrangement of partitions during division is different for different bacteria. In rod-shaped forms, it is located perpendicular to the long axis, in spherical forms, the partitions can be located in one, two or three mutually perpendicular planes, which is the reason for the formation of such forms as streptococci, tetracocci and sarcins.

The rate of reproduction of bacteria depends on a number of conditions and can be very different. The more favorable the external conditions for the existence of bacteria, the faster their division occurs. Under normal conditions, the number of bacteria doubles approximately every half hour. If it always happened unhindered, then the number of bacteria from one cell would reach colossal proportions. According to the microbiologist Kohn, the offspring of one bacillus in five days could fill all the seas and oceans. However, this has never happened and never will. The life cycle of bacteria is limited by certain external conditions, beyond which reproduction slows down or stops altogether. Lack of nutrition harmful products exchange, competition various kinds etc. have a detrimental effect on bacteria. Under adverse conditions, they die en masse.

Classification of bacteria

The position of bacteria in the system of living beings is not yet well defined. It is generally accepted that bacteria are part of the plant world, and fungi and algae are the closest related organisms to them. Morphological features of bacteria in most cases are limited to a few forms: spherical, rods, spirals. The extraordinary simplicity and elementary nature of their external organization make it difficult to classify them. Determining the species of a bacterium on the basis of morphological characters alone is impossible. Scientific systematics is based on morphology and developmental history, but to classify bacteria, it is necessary to know not only morphology, but also their physiological and biochemical characteristics. In this regard, the following are established: the ratio of bacteria to oxygen, temperature conditions, the formation of pigment, the liquefaction of gelatin, the formation of acids and gas on sugars, the change in milk during the growth of bacteria in it, the formation of indole, hydrogen sulfide, ammonia, the reduction of nitrates to nitrites or to free nitrogen . However, this is not always enough to determine the type of bacteria.

There are various classification systems for bacteria, but they are all conditional, and far more or less from the natural classification. Consideration of these systems or at least one of them in this case is not necessary even when applied to phytopathogenic bacteria. It should only be said that at present almost all phytopathogenic bacteria are united in the genera Pseudomonas, Xanthomonas, Bacterium and Erwinia.

Recently, M. V. Gorlenko (1961) proposed the following classification system for phytopathogenic bacteria of the class Eubacteriales:

I. Family Mycobacteriaceae(Chester, 1901) - non-motile bacteria (without flagella):

• 1st genus - Gorynebacterium (Leman and Neumann, 1896) - (gram-positive bacteria;
• 2nd genus Aplanobacterium (Smith, 1905, Geshich, 1956) - gram-negative bacteria.

II. Family Pseudomonadaceae(Wilson et al., 1917) - bacteria with flagella (polar):

• 1st genus - Pseudomonas (Migula, 1900) - unstained and fluorescent bacteria;
• 2nd genus - Xanthomonas (Dawson, 1839) - bacteria with colored colonies.

III. Family Bacteriaceae(Kon, 1872) - motile bacteria with peritrichous flagella that do not form supports:

• 1st genus - Bacterium (Ehrenberger, 1828) - unstained forms that do not form pectinases and protopectinases;
• 2nd genus - Pectobacterium (Waldy, 1945) - unstained forms that form pectinase and protopectinase;
• 3rd genus - Chromobacterium (Bergonzini, 1881) - colored forms.

IV. Family Bacillaceae(Fischer, 1895) - motile bacteria, spore-forming rods:

• 1st genus - Bacillus (Kon, 1832) - cells do not swell or swell slightly during spore formation;
• 2nd genus - Clostridium (Praznovsky, 1880) - cells swell during spore formation.

In the above system, the hitherto generally accepted genus Erwinia is omitted. A special genus Pectobacterium is isolated from it, which includes bacteria with peritrichous flagella and pectolytic activity. Those of the phytopathogenic bacteria that do not possess this ability are assigned to the genus Bacterium. This system, rational in itself, is new and has not yet entered into everyday life, therefore, in this work, we adhere to the classification in which the genus Erwinia is given its place. This generic name of phytopathogenic bacteria is widely used in the specialized literature both in our country and abroad.

Determining the type of bacteria without the use of artificial nutrient media is impossible. In this regard, it can be noted that when cultivating bacteria, they form very characteristic colonies. In this case, one appearance can be used to judge the species of bacteria.

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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.

Classification and morphology of microorganisms

Microbes- These are the smallest, mostly unicellular living organisms, visible only through a microscope. The size of microorganisms is measured in micrometers - microns (1/1000 mm) and nanometers - nm (1/1000 microns).

Microbes are characterized by a huge variety of species that differ in structure, properties, and the ability to exist in various environmental conditions. They can be unicellular, multicellular and non-cellular.

Microbes are divided into bacteria, viruses and phages, fungi, yeast. Separately, there are varieties of bacteria - rickettsia, mycoplasmas, a special group is made up of protozoa (protozoa).

bacteria

bacteria- predominantly unicellular microorganisms ranging in size from tenths of a micrometer, for example, mycoplasma, to several micrometers, and in spirochetes - up to 500 microns.

There are three main forms of bacteria - spherical (cocci), rod-shaped (bacilli, etc.), convoluted (vibrios, spirochetes, spirilla) (Fig. 1).

Globular bacteria (cocci) are usually spherical, but may be slightly oval or bean-shaped. Cocci can be located singly (micrococci); in pairs (diplococci); in the form of chains (streptococci) or grape bunches (staphylococci), a package (sarcinas). Streptococci can cause tonsillitis and erysipelas, staphylococci - various inflammatory and purulent processes.

Rice. 1. Forms of bacteria: 1 - micrococci; 2 - streptococci; 3 - sardines; 4 - sticks without spores; 5 - sticks with spores (bacilli); 6 - vibrios; 7- spirochetes; 8 - spirilla (with flagella); staphylococci

rod-shaped bacteria the most common. Rods can be single, connected in pairs (diplobacteria) or in chains (streptobacteria). The rod-shaped bacteria include Escherichia coli, pathogens of salmonellosis, dysentery, typhoid fever, tuberculosis, etc. Some rod-shaped bacteria have the ability to form under adverse conditions disputes. The spore-forming rods are called bacilli. Spindle-shaped bacilli are called clostridia.

Sporulation is a complex process. Spores differ significantly from a normal bacterial cell. They have a dense shell and a very small amount of water, they do not require nutrients, and reproduction completely stops. Spores are able to withstand drying, high and low temperatures for a long time and can be in a viable state for tens and hundreds of years (spores of anthrax, botulism, tetanus, etc.). Once in a favorable environment, the spores germinate, that is, they turn into the usual vegetative propagating form.

Convoluted bacteria can be in the form of a comma - vibrios, with several curls - spirilla, in the form of a thin twisted stick - spirochetes. Vibrios are the causative agent of cholera, and the causative agent of syphilis is spirochete.

bacterial cell has a cell wall (shell), often covered with mucus. Often the mucus forms a capsule. The cell membrane separates the contents of the cell (cytoplasm) from the membrane. The cytoplasm is a transparent protein mass in a colloidal state. The cytoplasm contains ribosomes, a nuclear apparatus with DNA molecules, and various inclusions of reserve nutrients (glycogen, fat, etc.).

Mycoplasmas- bacteria lacking a cell wall, requiring growth factors contained in yeast for their development.

Some bacteria can move. The movement is carried out with the help of flagella - thin threads of different lengths that perform rotational movements. Flagella can be in the form of a single long thread or in the form of a bundle, they can be located over the entire surface of the bacterium. Flagella are present in many rod-shaped bacteria and almost all curved bacteria. Spherical bacteria, as a rule, do not have flagella, they are immobile.

Bacteria reproduce by dividing into two parts. The rate of division can be very high (every 15-20 minutes), while the number of bacteria increases rapidly. This rapid division is seen in foods and other nutrient-rich substrates.

Viruses

Viruses- a special group of microorganisms that do not have a cellular structure. Viruses are measured in nanometers (8-150 nm), so they can only be seen with an electron microscope. Some viruses consist only of protein and one of nucleic acids(DNA or RNA).

Viruses cause common human diseases such as the flu, viral hepatitis, measles, as well as animal diseases - foot and mouth disease, animal plague and many others.

Bacterial viruses are called bacteriophages, fungal viruses mycophages etc. Bacteriophages are found wherever there are microorganisms. Phages cause microbial cell death and can be used to treat and prevent some infectious diseases.

Mushrooms are special plant organisms that do not have chlorophyll and do not synthesize organic substances, but need ready-made organic matter. Therefore, fungi develop on various substrates containing nutrients. Some fungi are capable of causing diseases of plants (cancer and late blight of potatoes, etc.), insects, animals and humans.

Fungal cells differ from bacterial cells in the presence of nuclei and vacuoles and are similar to plant cells. Most often they are in the form of long and branching or intertwining threads - hyphae. From hyphae it is formed mycelium, or mushroom. The mycelium may consist of cells with one or more nuclei, or be non-cellular, representing one giant multinucleated cell. Fruiting bodies develop on the mycelium. The body of some fungi may consist of single cells, without the formation of mycelium (yeast, etc.).

Fungi can reproduce in a variety of ways, including vegetatively by dividing hyphae. Most fungi reproduce asexually and sexually through the formation of special reproductive cells - dispute. Spores, as a rule, are able to persist in the external environment for a long time. Mature spores can be transported over considerable distances. Once in the nutrient medium, spores quickly develop into hyphae.

Mold fungi represent an extensive group of fungi (Fig. 2). Widely distributed in nature, they can grow on food products, forming well-visible plaques of different colors. Food spoilage is often caused by mucor fungi, which form a fluffy white or gray mass. The mucosal fungus rhizopus causes “soft rot” of vegetables and berries, and the botrytis fungus coats and softens apples, pears and berries. The causative agents of molding products can be fungi from the genus Peniiillium.

Certain types of fungi can not only lead to food spoilage, but also produce substances that are toxic to humans - mycotoxins. These include some types of fungi of the genus Aspergillus, the genus Fusarium, etc.

The beneficial properties of certain types of mushrooms are used in the food and pharmaceutical industries and other industries. For example, fungi of the genus peniiillium are used to produce the antibiotic penicillin and in the production of cheeses (Roquefort and Camembert), fungi of the genus Aspergillus are used in the production citric acid and many enzyme preparations.

actinomycetes- microorganisms that have characteristics of both bacteria and fungi. By structure and biochemical properties, actinomycetes are similar to bacteria, and by the nature of reproduction, the ability to form hyphae and mycelium, they are similar to fungi.

Rice. 2. Types of mold fungi: 1 - peniiillium; 2- aspergillus; 3 - mukor.

Yeast

Yeast- unicellular immobile microorganisms no larger than 10-15 microns in size. The shape of the yeast cell is more often round or oval, less often rod-shaped, sickle-shaped or similar to a lemon. Yeast cells are similar in structure to mushrooms, they also have a nucleus and vacuoles. Yeast reproduction occurs by budding, division or spores.

Yeasts are widely distributed in nature, they can be found in the soil and on plants, on food products and various waste products containing sugars. The development of yeast in food products can lead to spoilage, causing fermentation or souring. Some types of yeast have the ability to convert sugar into ethyl alcohol and carbon dioxide. This process is called alcoholic fermentation and is widely used in the food and wine industry.

Some types of Candida yeast cause a human disease called candidiasis.

1.5. Modern classification bacteria In modern taxonomy of bacteria, a situation has developed that is also characteristic of the classification of other organisms: progress has been made in creating a phylogenetic classification system that reflects the main directions of evolutionary development and the relationship of representatives of certain taxa, but artificial phenotypic classifications more convenient for the identification of microorganisms. At present, there is no any detailed evolutionary system of prokaryotes and, most likely, the solution of this problem is not a matter of the near future. Features of prokaryotes in the field of morphological, physiological, biochemical, and genetic organization indicate the inapplicability to them of well-developed principles used in the construction of a system of higher organisms. Not stopping at historical aspects problems of taxonomy of bacteria, it should be noted that the most acceptable phylogenetic classification system for prokaryotes is a system based on matching the nucleotide sequence in 16S-rRNA. This system is the basis of the 2nd edition of the multi-volume encyclopedia of prokaryotes - Bergey's Manual of Systematic Bacteriology (Bergey's Guide to Systematic Bacteria), the first volume of which was published in 2001. In this work, all prokaryotes are divided into 26 phylogenetic "branches" (groups ) based on the structure of their 16S-rRNA; 23 "branches" are represented by eubacteria, and three by archaebacteria. It should be emphasized that a large number of these phylogenetic groups contain prokaryotic species that have not been isolated as pure cultures and therefore have not yet been studied in detail. For representatives of these species, only the 16S rRNA nucleotide sequences are currently known. Of the 23 groups of eubacteria, two phylogenetic groups are represented by gram-positive bacteria, the remaining groups are gram-negative. Gram-negative bacteria consist of a large group of Proteobacteria (Proteobacteria) and 20 groups of other bacteria with this type of cell wall. a brief description of Proteobacteria, to which the mitochondria and chloroplasts of most eukaryotes are closest in terms of 16S-rRNA composition, are shown in Table 1. 2. Proteobacteria are a group of gram-negative bacteria that is very heterogeneous in morphological, physiological and biochemical terms. Representatives of this group are characterized by all types of energy metabolism and nutrition. The cells of most species of Proteobacteria have a rod-shaped, spherical, or vibrioid shape, multiply mainly by binary fission, but some species are characterized by budding and the formation of fruiting bodies in a complex cell cycle. This group contains both motile due to flagella and immobile bacteria. With respect to molecular oxygen, Proteobacteria are classified as obligate aerobes, obligate and facultative anaerobes. The Proteobacteria group is divided into five subgroups based on differences in 16S rRNA: alpha, beta, gamma, delta, and epsilon. In addition to Proteobacteria, the following main groups of eubacteria are gram-negative: hydrogen thermophiles, green filamentous bacteria, green sulfur bacteria, cyanobacteria, spirochetes, cytophages, bacteroids, chlamydia, planctomycetes, deinococci, chloroflexus, fusobacteria, fibrobacteria, thermodesulfobacteria, etc. Phylogenetic groups gram-positive bacteria - Actinobacteria and Firmicutes. The Actinobacteria group (“actinomycete branch”) is represented by the following genera of bacteria with a high content of GC pairs in DNA: Geodermatophilus, Frankia, Streptomyces, Arthrobacter, Micrococcus, Actinomyces, Bifidobacterium, Propionibacterium, Actinoplanes, Nocardia, Rhodococcus, Corynebacterium, Mycobacterium. The Firmicutes group (“clostridial branch” - mainly gram-positive bacteria with a low content of GC-pairs in DNA) consists of the following genera: Clostridium, Lactococcus, Pediococcus, Streptococcus, Enterococcus, Leuconostoc, Listeria, Caryophanon, Staphylococcus, Sarcina, Sporosarcina, Bacillus, Desulfotomaculum, Heliobacterium, Mycoplasma, Ureaplasma, etc. Archaebacteria are divided into three phylogenetic groups: Crenarchaeota, Euryarchaeota and Korarchaeota. The Crenarchaeota group consists of extremely thermophilic bacteria, most of whose representatives metabolize sulfur, some reduce iron and molybdenum ions. The Euryarchaeota group includes obligate anaerobic methanogenic archaebacteria, as well as extreme thermophiles and halophiles. The Korarchaeota group is formed by archaebacteria that live in hot sulfur springs. To date, none of the representatives of this group (possessing similar 16S rRNA) has been isolated as a pure culture; therefore, their phenotypic features have not been studied enough. Concluding the consideration of the phylogenetic branches of prokaryotes, it should be noted that the proposed phylogenetic system, based on the study of the nucleotide sequences of only one ribosomal RNA gene, is nothing more than one of the technically convenient and developed systems for ordering numerous organisms in order to identify them; therefore, it is logical to construct correct taxonomy of bacteria only taking into account this feature is not possible. The most recognized and used phenotypic classification of bacteria is that presented in the ninth edition of Burgey's Guide to Bacteria. In this edition, bacteria are divided into four main categories (divisions) based on the structure of the cell boundary layer: 1) Gracilicutes (from Latin cutes - skin, gracilis - thin) - gram-negative eubacteria with cell walls; 2) Firmicutes (from lat. firmus - strong) - gram-positive eubacteria with cell walls; 3) Tenericutes (from Latin tener - soft, tender) - eubacteria, devoid of cell walls; 4) Mendosicutes (from Latin mendosus - erroneous) - archaebacteria, the cell walls of which differ from similar structures of other prokaryotes. The Gracilicutes department includes bacteria of various morphologies with a Gram-negative cell wall. Reproduction occurs mainly by binary fission, some bacteria reproduce by budding. Endospore does not form. Most are motile: there are all types of movement of bacteria - with the help of flagella, sliding, bending. The division includes aerobic, anaerobic, and facultative anaerobic bacteria; phototrophic and chemotrophic bacteria. The department is divided into three classes: Scotobacteria, Oxyphotobacteria, Anoxyphotobacteria. The class Scotobacteria includes gram-negative bacteria that do not use light energy for metabolic purposes, but receive it only as a result of redox reactions. The name of the class comes from the Greek sсotos - darkness. This is the largest class of bacteria. The class Anoxyphotobacteria includes purple bacteria, green bacteria, and heliobacteria, which carry out anoxygenic photosynthesis (without the release of molecular oxygen). The class Oxyphotobacteria is represented by cyanobacteria and prochlorophytes that carry out oxygenic photosynthesis (with the release of molecular oxygen). This type of photosynthesis is similar to the photosynthesis that occurs in plants. The Firmicutes department includes bacteria with a Gram-positive cell wall. Cells can have different shapes: rods, cocci, filamentous, branching. Some representatives form endospores. Most of them are motionless; motile forms have peritrichous flagella. The department includes aerobic, anaerobic and facultative anaerobic bacteria. The department consists of two classes: Firmibacteria, Thallobacteria. The class Firmibacteria includes a large number of "non-branching" Gram-positive bacteria. The class Thallobacteria includes bacteria whose cells are capable of "branching". The Tenericutes department is represented by bacteria that do not have a cell wall. Due to the absence of a cell wall, the shape of the cells is not constant: in a pure culture of one species, coccoid, rod-shaped, filamentous, pear-shaped, disc-shaped, and other cells are simultaneously present. The reproduction of bacteria included in this section occurs by binary fission, budding. Gram stain is negative. The formation of small colonies growing into agar is characteristic. They can be saprophytic, parasitic or pathogenic. The department consists of one class Mollicutes (mycoplasmas). The Mendosicutes division is formed by bacteria with a rigid cell wall but lacking murein peptidoglycan. Most representatives are strict anaerobes, many of which have flagella. Species are characterized by ecological and metabolic diversity, the ability to live in extreme conditions. The department consists of one class - Archaebacteria. As part of four divisions (main categories), 35 groups (or sections) of bacteria have been identified, which will be characterized to a greater or lesser extent in subsequent chapters. The following groups belong to the department Gracilicutes. Group 1. Spirochetes. Group 2. Aerobic (or microaerophilic), motile, spiral (or vibrioid) Gram-negative bacteria. Group 3. Non-motile or rarely motile Gram-negative curved bacteria. Group 4. Gram-negative aerobic (or microaerophilic) rods and cocci. Group 5. Optional aerobic gram-negative rods. Group 6. Gram-negative anaerobic straight, curved or spiral rods. Group 7. Bacteria performing dissimilation reduction of sulfur or sulfate. Group 8. Anaerobic gram-negative cocci. Group 9. Rickettsia and chlamydia. Group 10. Anoxygenic phototrophic bacteria. Group 11. Oxygenic phototrophic bacteria. Group 12. Aerobic chemolithotrophic bacteria and related organisms. Group 13. Budding and (or) outgrowth-forming bacteria. Group 14. Bacteria with sheaths. Group 15. Non-photosynthetic gliding bacteria that do not form fruiting bodies. Group 16. Gliding bacteria forming fruiting bodies. The department Firmicutes includes: Group 17. Gram-positive cocci. Group 18. Gram-positive rods and cocci that form endospores. Group 19. Gram-positive rods of the correct form, which do not form spores. Group 20. Irregularly shaped Gram-positive rods that do not form spores. Group 21. Mycobacteria. Groups 22–29. Actinomycetes. To the department Tenericutes belongs: Group 30. Mycoplasmas. Division Mendosicutes includes: Group 31. Methanogens. Group 32. Sulfate-reducing archaebacteria. Group 33. Extremely halophilic archaebacteria (halobacteria). Group 34. Archaebacteria lacking a cell wall. Group 35 Extremely thermophilic and hyperthermophilic sulfur-metabolizing archaebacteria. In conclusion, it should be emphasized that the majority of microorganisms existing in natural communities still need to be isolated into pure cultures. It is believed that at present only 0.1% of the total microbial diversity can be cultivated, and it is not possible to grow and identify the remaining representatives of bacteria, although about 5 thousand species of prokaryotes have already been isolated and described in pure culture.

What are bacteria: types of bacteria, their classification

Bacteria are tiny microorganisms that have been around for thousands of years. It is impossible to see microbes with the naked eye, but we should not forget about their existence. There are a huge number of bacilli. The science of microbiology is engaged in their classification, study, varieties, features of structure and physiology.

Microorganisms are called differently, depending on their kind of actions and functions. Under a microscope, you can observe how these little creatures interact with each other. The first microorganisms were rather primitive in form, but their importance should by no means be underestimated. From the very beginning, bacilli evolved, created colonies, tried to survive in changing climatic conditions. Different vibrios are able to exchange amino acids in order to grow and develop normally as a result.

Today it is difficult to say how many species of these microorganisms are on earth (this number exceeds a million), but the most famous and their names are familiar to almost every person. It doesn’t matter what microbes are and what they are called, they all have one advantage - they live in colonies, so it is much easier for them to adapt and survive.

First, let's figure out what microorganisms exist. The simplest classification is good and bad. In other words, those that are harmful to the human body, cause many diseases and those that are beneficial. Next, we will talk in detail about what are the main beneficial bacteria and give a description of them.

You can also classify microorganisms according to their shape, characteristics. Probably, many people remember that in school textbooks there was a special table with the image of various microorganisms, and next to it was the meaning and their role in nature. There are several types of bacteria:

• cocci - small balls that resemble a chain, as they are located one behind the other;
• rod-shaped;
• spirilla, spirochetes (have a convoluted shape);
• vibrios.

Bacteria of different shapes

We have already mentioned that one of the classifications divides microbes into species depending on their shape.

Bacteria coli also have some features. For example, there are types of rod-shaped with pointed poles, with thickened, with rounded or with straight ends. As a rule, rod-shaped microbes are very different and are always in chaos, they do not line up in a chain (with the exception of streptobacilli), they do not attach to each other (except for diplobacilli).

To microorganisms of spherical forms, microbiologists include streptococci, staphylococci, diplococci, gonococci. It can be pairs or long chains of balls.

Curved bacilli are spirilla, spirochetes. They are always active but do not produce spores. Spirilla is safe for people and animals. You can distinguish spirilla from spirochetes if you pay attention to the number of curls, they are less convoluted, have special flagella on the limbs.

Types of pathogenic bacteria

For example, a group of microorganisms called cocci, and in more detail streptococci and staphylococci cause real purulent diseases (furunculosis, streptococcal tonsillitis).

Anaerobes live and develop perfectly without oxygen; for some types of these microorganisms, oxygen generally becomes deadly. Aerobic microbes need oxygen to survive.

Archaea are almost colorless unicellular organisms.

Pathogenic bacteria should be avoided because they cause infections, gram-negative microorganisms are considered resistant to antibodies. There is a lot of information about soil, putrefactive microorganisms, which are harmful, useful.

In general, spirilla are not dangerous, but some species can cause sodoku.

Varieties of beneficial bacteria

Even schoolchildren know that bacilli are useful and harmful. People know some names by ear (staphylococcus, streptococcus, plague bacillus). These are harmful creatures that interfere not only with the external environment, but also with humans. There are microscopic bacilli that cause food poisoning.

Must know useful information about lactic acid, food, probiotic microorganisms. For example, probiotics, in other words good organisms, are often used for medical purposes. You ask: for what? They do not allow harmful bacteria to multiply inside a person, strengthen the protective functions of the intestine, and have a good effect on the human immune system.

Bifidobacteria are also very beneficial for the intestines. Lactic acid vibrios include about 25 species. In the human body, they are present in large quantities, but are not dangerous. On the contrary, they protect the gastrointestinal tract from putrefactive and other microbes.

Speaking of good ones, one cannot fail to mention the huge species of streptomycetes. They are known to those who took chloramphenicol, erythromycin and similar drugs.

There are microorganisms such as Azotobacter. They live in the soil for many years, have a beneficial effect on the soil, stimulate the growth of plants, cleanse the earth of heavy metals. They are irreplaceable in medicine, agriculture, medicine, food industry.

Types of bacterial variability

By their nature, microbes are very fickle, they die quickly, they can be spontaneous, induced. We will not go into details about the variability of bacteria, since this information is of more interest to those who are interested in microbiology and all its branches.

Types of bacteria for septic tanks

Residents of private homes understand the urgent need to treat wastewater, as well as cesspools. Today, drains can be quickly and efficiently cleaned with the help of special bacteria for septic tanks. For a person, this is a huge relief, since cleaning the sewer is not a pleasant thing.

We have already clarified where the biological type of wastewater treatment is used, and now let's talk about the system itself. Bacteria for septic tanks are grown in laboratories, they kill the unpleasant smell of drains, disinfect drainage wells, cesspools, reduce the volume Wastewater. There are three types of bacteria that are used for septic tanks:

• aerobic;
• anaerobic;
• live (bioactivators).

Very often people use combined cleaning methods. Strictly follow the instructions on the preparation, make sure that the water level contributes to the normal survival of bacteria. Also, remember to use the drain at least once every two weeks so that the bacteria have something to eat, otherwise they will die. Don't forget that chlorine from cleaning powders and liquids kills bacteria.

The most popular bacteria are Dr. Robik, Septifos, Waste Treat.

Types of bacteria in urine

In theory, there should be no bacteria in the urine, but after various actions and situations, tiny microorganisms settle where they please: in the vagina, in the nose, in water, and so on. If the bacteria were found during the tests, this means that the person is suffering from diseases of the kidneys, bladder or ureters. There are several ways in which microorganisms enter the urine. Before treatment, it is very important to investigate and accurately determine the type of bacteria and the route of entry. This can be determined by biological urine culture, when the bacteria are placed in a favorable habitat. Next, the reaction of bacteria to various antibiotics is checked.

We wish you to always stay healthy. Take care of yourself, wash your hands regularly, protect your body from harmful bacteria!