Systematics is a branch of biology that studies organisms from the point of view of their morphological similarities and differences, reveals common features and the degree of relationship between organisms based on their origin (phylogenesis) and historical development, distributing organisms into groups - systematic categories. The establishment of a natural science classification (taxonomy) of living organisms greatly facilitates their study. The need to study microorganisms in all the diversity of their vital manifestations and mutual relations urgently required the establishment of certain taxonomic categories in the world of microbes. However, the creation of a natural science classification of microbes proved to be extremely difficult.

Particularly great difficulties are encountered in the taxonomy of bacteria due to the insufficiency of our knowledge about historical paths their development, and also because of the apparent simplicity and elementary nature of the external organization of bacteria, which, moreover, depends on the environment.

The basis of the classification is the species - the basic unit of the evolutionary development of organic nature. Determining the type of microorganism is a task much more difficult than determining the type higher plants or animals. For a botanist or zoologist, a cursory glance is sometimes enough to determine the species of a given plant or animal; the microbiologist, for this, has to carry out a series of painstaking microbiological studies. First, the main features of the studied microbe are established. According to these features, the microbe is identified (identified) by the determinant with the previously described species and its place is found in the classification of microbes.

The concept of species is a very important and at the same time complex issue in the systematics of microorganisms. The species of microbes, based on modern scientific data, is considered as a set of related organisms: a) having a common root of origin; b) isolated as a result of selection; c) adapted to a certain habitat; d) having a similar metabolism, the nature of interspecies relations; e) close to each other in morphological, physiological characteristics and genetic apparatus. For pathogenic types of microbes, the ability to cause the formation of certain protective substances - antibodies in the body of animals and humans (K. Pyatkin) is also taken into account.

Morphological signs of a microorganism are signs observed directly under a microscope on living and dead preparations: the shape, size and natural combination of cells, the ability to move, spore formation, the location of spores in a cell, the ability to form capsules. Since these signs are uniform, they allow us to determine only ancestry the studied microbe (bacteria, bacilli, micrococci, streptococci, etc.).

Cultural traits are traits obtained by observing the development of a culture of a given microbe in various nutrient media. By nature, cultural features partially consist of morphological features (shape, color, luster of the colony on the surface of a solid nutrient medium or in its thickness, the nature of the edges of the colony, its structure, the growth of a microbe in meat-peptone broth, etc.) and physiological features (features of nutrition and respiration , attitude to temperature, the nature of metabolic products, the ability to coagulate milk, thin gelatin, etc.).

Only the complete identification of the entire set of morphological and cultural characteristics of a microorganism makes it possible to determine its species and distinguish it from related species. Thus, in order to obtain the most complete species characteristics of a microorganism, in addition to microscopy, although its methods are subtle and relatively quickly performed, the widest and most versatile observations of the development of the microbe culture under study are necessary, and for pathogenic microbes, a whole series of specific bacteriological analyzes.

The name of microbial species in microbiology is given according to the principle of double (binary) nomenclature, proposed by Carl Linnaeus. According to this nomenclature, each type of microbe has a generic and specific name. The generic name is written with capital letter, specific - with lowercase. Species are combined into genera, genera into even higher system categories - families, families - into orders, orders - into classes and departments. The generic name of a microbe denotes either some morphological feature, or the name of the scientist who discovered it. The species name most often refers to the color, the most likely habitat of the microbe, or means a disease caused by the microbe, etc. For example, the name Bacillus subtilis indicates that the microorganism is a spore-forming bacillus that stains according to Gram (properties of the genus Bacillus), and subtilis in Latin "hay" , i.e. "hay stick"; Escherichia colii - Escherichia coli; Escherichia - named after the famous German scientist Escherich; colitis - department of the large intestine; Clostridium botulinum is a spore-forming bacillus that develops only in the absence of oxygen (properties of the genus Clostridium); botulus - in Latin "sausage" (the microbe was first discovered in sausages), etc.

Classification of bacteria

One of the first classification systems for bacteria was developed by F. Cohn in 1872. This system was based solely on the morphological principle. In 1897, Migula proposed a system that, in addition to morphological features, also took into account some physiological ones, such as nitrogen fixation. In 1909, Orla-Jensen created a system based mainly on the physiological principle. In 1896, K. Lehman and R. Neumann developed a classification of bacteria, which laid the foundation for the creation of a scientifically based systematics of microbes. The classification of bacteria by Lehmann and Neumann was gradually improved by the authors themselves. As the most successful of all the proposed classifications, the most clear and simple enough, with certain changes and additions, it is used for practical needs in food microbiology at the present time.

In medical microbiology, the classification of bacteria proposed by the committee of American bacteriologists is adopted. In the guide, published in 1924, edited by D. Burge, all bacteria (class Schizomycetes - crushing fungi) are divided into 10 orders, each order is divided into families, families - into genera, genera - into species. This key describes more than 1500 species of bacteria. Berge's classification, however, is not without flaws. In particular, it does not take into account the variability of microbes and their evolutionary development. In addition, the type of microorganism is considered not as a qualitative stage in the development of wildlife, but "as a concept accepted in systematics."

The Soviet scientist, Corresponding Member of the Academy of Sciences of the USSR N. A. Krasilnikov (1949) systematizes microorganisms, taking into account their origin and evolutionary development, and gives a generally accepted description of over 6,000 types of microorganisms (bacteria and actinomycetes). This is the most thoughtful and complete classification among the proposed modern systematics, taking into account both morphological and cultural features of microbes.

Below is the simplest taxonomy of Lehmann and Neumann bacteria, which satisfies the requirements of practice, with appropriate changes and additions. In this taxonomy, the division of bacteria into families is based on the external shape of the cells and the ability to sporulate. The division into genera is carried out on the basis of the location of the dividing septum and the degree of tortuosity of the cell. The species affiliation is determined on the basis of cultural (and physiological) characteristics.

All bacteria and actinomycetes, according to the classification of Lehmann and Neumann, are assigned to one class of crushing fungi Schizomycetes, divided into two orders: 1) true, or real, crushing fungi - schizomycetes (Schizomycetales) and 2) radiant fungi - actinomycetes (Actinomycetales).

Schizomycete order includes six families.

I. Family of cocci (family Cossaceae). This family includes spherical bacteria that reproduce by simple division. Cocci do not form spores; they stain positively according to Gram, although Gram-negative species are also found in rare cases. These are immobile microorganisms; on solid media they form both colorless and colored colonies.

The cocci family is subdivided into the following genera:

1) micrococci (Micrococcus);

2) streptococci (Streptococcus);

3) Sarcina (Sarcina);

4) staphylococci (Staphylococcus);

5) tetracocci (Tetracoccus);

6) diplococci (Diplococcus).

II. Bacillus family (family Bacillaceae). This family includes spore-bearing rods, usually gram-positive, motile, with flagella. There are, however, forms in which mobility is not found. The family includes two genera:

1) the genus of bacilli (Bacillus). Spore-forming rods that develop with the access of atmospheric oxygen;

2) the genus Clostridium (Clostridium). Spore-forming rods that develop without access to atmospheric oxygen.

III. Family of bacteria (family Bacteriaceae). Non-spore-bearing Gram-negative motile rods. Burning is in most cases peritrichous; reproduce by division. The family includes the genus of bacteria (Bacterium).

IV. Desmobacteria family (family Desmobacteriaceae). This includes multicellular bacteria that look like long filaments of interconnected cells. Of the desmobacteria, sulfur bacteria and iron bacteria are important, taking part in the transformations of sulfur and iron in nature.

V. The family of spirilla (convoluted bacteria) (family Spirillaceae). These include the genus Vibrios (Vibrio) and the genus Spirilla (Spirillum).

VI. Spirochete family (family Spirochaetaceae). The family is divided into several genera; some of the genera are pathogenic to humans. The main genus is spirochetes (Spirochaeta).

Actinomycete order(Actinomycetales). Bacteria of this order are also called radiant fungi, they belong to unicellular microorganisms. Actinomycetes are widely distributed in nature. They are especially common in the soil, on various animal and plant remains; can cause food spoilage with the formation of a specific earthy odor.

The body of actinomycetes consists of mycelium in the form of branching non-septate filaments (hyphae) (Fig. 16). Sometimes the mycelium branches weakly. During the development of actinomycetes on nutrient media, one part of the mycelium is immersed in the substrate, the other is in the air above the substrate in the form of a fluffy "air mycelium". However, individual representatives of this order may also have a smooth surface.

In young cells of actinomycetes, the cytoplasm looks like a homogeneous mass containing separate grains of chromatin (nuclear substance). As cells age, vacuoles, fat droplets, appear in their cytoplasm. The cell membrane becomes fragile, easily destroyed, and partial lysis (dissolution) of the cells occurs.

No differentiated nucleus was found in actinomycete cells. Actinomycetes reproduce by conidia (exospores), which are easily laced on the aerial filaments of the mycelium. Colonies of actinomycetes are different in size and color (can be black, brown, red, green, etc.).

Actinomycetes include tuberculosis, diphtheria bacteria. Some actinomycetes cause severe diseases in humans and animals, accompanied by the destruction of tissues and bones (actinomycosis). There are among actinomycetes and such forms that produce specific substances that have a detrimental effect on other microorganisms. These substances are called antibiotics (for example, streptomycin, produced from the radiant fungus Actinomyces globisporus streptomycini). Antibiotics are widely used as medicines.

mushroom classification

The study of mold fungi has always gone hand in hand with the study of bacteria. This is due to the fact that fungi are extremely widespread in nature. The air is especially rich in mold spores. In addition, fungi cause contamination of bacterial cultures, so that bacteriologists have to meet with them very often. According to morphological and physiological characteristics, fungi are divided into five classes.

I class - archymycetes(Archimycetes). These are the lowest, most simply arranged mushrooms. They are completely devoid of mycelium. The vegetative development of fungi is carried out at the expense of a bare or, at a later age, a lump of cytoplasm protected by a membrane. Archymycetes reproduce by spores and by mobile uniflagellate zoospores.

II class - phycomycetes(Phycomycetes). This class includes fungi that have non-septate multinucleated mycelium and are capable of both sexual and asexual reproduction. During sexual reproduction in some phycomycetes, united in the subclass of oomycetes (Oomycetes), two differentiated cells (male and female) merge to form an oospore. Another part of phycomycetes is assigned to a subclass of zygomycetes (Zygomycetes). During sexual reproduction, two undifferentiated cells fuse to form a zygospore.

From oomycetes highest value has the causative agent of the disease of stems and tubers of potatoes, eggplants, tomatoes - phytophthora (Phytophthora infestans) and the fungus that causes the disease of grapes - mildew, called Plasmopara viticola. During asexual reproduction, oomycetes very often form mobile zoospores, equipped with one flagellum.

Typical representatives of zygomycetes are fungi of the Mucoraceae family (Mucoraceae), genera Mucor, Rhizopus, Tamnidium. Asexual reproduction in them is carried out by immobile sporangiospores. In the genus Mucor, large sporangia are formed on single or branching sporangiophores. In the genus Rhizopus, non-branching sporangiophores, colored in dark brown, grow in bushes. At the base of such a bush of sporangiophores, thin root-like processes of hyphae - rhizoids appear. Rhizopuses spread along the surface of the substrate with the help of long hyphae - stolons, resembling strawberry tendrils. Fungi of the genus Thamnidium produce two types of sporangia. A large multi-spored sporangium is formed at the top of the sporangiophore, and small sporangioles with a relatively small number of spores develop on the side branches of the same sporangiophore. In the class of phycomycetes, there are up to 700 species of fungi. Many phycomycetes are causative agents of food spoilage.

III class - marsupial mushrooms(Ascomycetes). This class is subdivided into two orders: primary marsupial, or golomarsupial, fungi (Protascales), in which bags grow directly on the mycelium without the formation of a special fruiting body, and compound marsupial, or fruit marsupial, mushrooms (Plectascales).

Yeasts belong to the fungi. Yeast classification is given below. Of the filamentous gonomarsupial fungi, the most important representative is the genus Endomyces (Endomyces vernalis), called fatty yeast because of its ability to accumulate in cells a large number of fat. The mycelium of the fungus of the genus Endomyces very often breaks up into individual cells that reproduce, like yeast, by budding.

Aspergillus, penicillium molds, as well as common pathogens of diseases of fruits, vegetables, cereals: ergot (Claviceps purpurea), sclerotinia (Sclerotinia libertiana), valuable edible mushrooms - truffles and morels. In general, ascomycetes include up to 20 thousand species, different in structure and properties.

IV class - basidiomycetes(Basidiomycetes). Fungi of this class are also able to reproduce both sexually and asexually. Their main organ of sexual reproduction is the basidium with basidiospores. Basidiomycetes - an extensive group of fungi, numbering about 20 thousand species. This class includes the following mushrooms:

hat, fruiting body which is a hat attached to the leg; With inside caps between radially diverging plates or in tubes are basidia; many hat mushrooms are edible, but there are also poisonous ones;

brownies, the most important representative of which is the energetic destroyer of wood - the fungus Merulius lacrymans ("weeping");

tinder fungi of the genera Fomes (Fotnes) and polyporus (Polyporus), developing in the form of spatulate or fan-shaped growths on the trunks of affected trees and on dead wood (the growth is a perennial fruiting body);

Class V - imperfect mushrooms(Fungi imperfecti). This class includes up to 25 thousand species of multicellular fungi in which sexual reproduction has not been found. These fungi reproduce either through conidia (most) or oidia, and some do not have any reproductive organs at all. Conidiophores in imperfect fungi develop on the mycelium either in groups or singly. The most important genera of this class are: oidium, botrytis, fusarium, cladosporium, alternaria, catenularia, monilia (Fig. 17).

In the genus Botrytis (Botrytis), tree-branching conidiophores end in a mass of small conidia that form clusters resembling a bunch of grapes. The conidia are grey. Botrytis causes neck rot onion, as well as gray rot of fruits, vegetables (carrots, cabbage, tomatoes), grapes, raspberries, strawberries. Botrytis cinerea, together with other fungi, is the causative agent of sugar beet clamp rot.

Some types of Fusarium form gibberellic acid, which has a pronounced ability to activate the growth of a number of plants. Obtained preparations of gibberellic acid in Lately found application in agriculture as plant growth stimulants.

In the genus Alternaria (Alternaria), on short lateral branches of vegetative hyphae, playing the role of conidiophores, single or multicellular conidia connected by short chains are formed, having a rounded pear-shaped or pointed-elongated shape. The mycelium of the mushroom is almost black. Alternaria causes black rot of various root crops (carrots, parsley). Damage appears as dark, almost black, depressed spots scattered over the surface of the root crop.

Cladosporium (Cladosporium) has erect conidiophores, rapidly falling conidia of various shapes (round, oval or elongated) develop on them. Cladosporium conidia may have one or more septa or none at all. The mycelium and conidia of the cladosporium are dark olive in color. Most often, cladosporium causes spoilage of food - meat; oils, cheeses, eggs, forming hard-to-remove black spots on the surface of these products.

On slowly growing colonies of catenularia (Catenularia), true conidiophores do not arise. At the ends of ordinary hyphae, very long chains of small shiny dark brown conidia are formed, similar to a necklace. Catenularis fuliginea ("chocolate mold") causes spoilage of sweetened condensed milk, forming chocolate-colored lumps and pads in it.

Mushrooms of the genus Foma (Phoma) form black-colored pycnidia. Very short conidiophores appear inside the pycnidia, bearing small, colorless spores. Individual members of this genus cause beet heart rot (Phoma betae) and spoilage. butter(Phoma pigmentivora).

Mushrooms of the genus Monilia (Monilia) are, as it were, a transitional form from unicellular budding fungi to multicellular ones. They reproduce by budding, which resembles the development of yeast. This results in ovoid yeast-like conidia. It was mentioned above that individual representatives of the genus Monilia are the causative agents of fruit rot of pome and stone fruits. The species Monilia murmanica is used for the production of fodder (protein) yeast.

Yeast classification

The classification of yeasts is based on the difference in their physiological characteristics and methods of reproduction (budding, division, sporulation). In 1954, V. I. Kudryavtsev developed a classification of true yeasts.

True yeasts are united in the family of saccharomycetes (Saccharomycetaceae) - sugar fungi. These are cultural, economically important yeasts. They reproduce by budding; sporulation occurs both after cell copulation and parthenogenetically. The spores are spherical in shape, covered with a single membrane.

The main genus is Saccharomyces. According to the ability to ferment glucose, sucrose, maltose, lactose, the species of this genus are divided into six sugar groups.

Beer and baker's yeast, yeast used in the alcohol industry, are assigned to the species cerevisiae (Sacch. cerevisiae), wine yeast - to the species saccharomyces ellipsoideus (Sacch. ellipsoideus). Both of these species are divided into a very large number of races. Races differ from each other in certain properties - fermentation energy, the amount of alcohol formed, lift, etc. Certain properties of yeast races are taken into account in the corresponding production, since they are important condition to obtain a high quality product.

False yeasts are united in the family of non-saccharomycetes (Non-Saccharomycetaceae). These yeasts also reproduce by budding, but do not form spores. The most important are the genera Torula, Mycoderma, and Endomyces.

MINISTRY OF EDUCATION AND SCIENCE, YOUTH AND SPORT

DONETSK NATIONAL UNIVERSITY OF ECONOMICS AND TRADE NAMED AFTER MIKHAIL TUGAN-BARANOVSKY

Department of Commodity Science and Expertise of Food Products

Kudinova O.V.

"microbiology"

Lecture notes

By discipline

for students of the professional direction - 6.030510.01.01 - "Commodity research of non-food products and commercial activity»

Donetsk 2011
Module 1

Topic: Fundamentals of classification and morphology of microorganisms

1. Systematics, classification and nomenclature of microorganisms.

2. Dimensions, shape, structure and mobility of a bacterial cell.

3. general characteristics mushrooms.

3.1. Structure and methods of reproduction.

3.2. Systematics of mushrooms.

3.3. General characteristics of yeast.

Systematics, classification and nomenclature of microorganisms.

Microorganisms (bacteria, fungi, protozoa, viruses) are systematized according to their similarities, differences and relationships with each other. This is what special science is doing - taxonomy of microorganisms .

Classification - a section of taxonomy that distributes microorganisms into taxonomic categories - taxa (from Greek. taxis- location, order) based on the similarity of homogeneous features. The taxonomy of microorganisms is based on their morphological, physiological, biochemical and molecular biological properties. The more information is available about microorganisms, the more accurately they can be assigned to the appropriate taxonomic category. There are the following main taxonomic categories: kingdom, department, class, order, family, genus, species.

Nomenclature is a system of naming taxonomic categories in accordance with international rules.

One of the main taxonomic categories is the species (species). View is a collection of individuals with common origin, close to each other in genetic, morphological and physiological characteristics, adapted to a certain habitat, having a similar metabolism and the nature of interspecific relationships.

In microbiology, as in biology, a double (binary) nomenclature is adopted to designate a species of bacteria, which is characterized by the fact that each microorganism has a generic and specific name.

If, when studying bacteria, deviations from typical species properties are found, then such a culture is considered as subspecies .Distinguish also types (options) , i.e. intraspecific subdivisions, which are based on the difference between individuals by some small hereditary properties.

A group of homogeneous microorganisms growing on culture medium, which has similar morphological, tinctorial (relation to dyes), cultural, biochemical and antigenic properties, is called pure culture .

A pure culture of microorganisms isolated from a specific source and different from other members of the species is called strain.

Close to the strain is the concept of a clone. Clone is a collection of individuals grown from a single microbial cell.

The American microbiologist D. Bergi (1938-1999) released the first international bacterial determinant. Subsequent editions of the determinant called "Bergey's Manual of Determinative Bacteriology" were prepared by the International Committee on the Systematics of Bacteria. They provide detailed and complete latest information about microorganisms, their taxonomy, nomenclature and principles of identification, ecological characteristics (habitat, niches) and other properties are given. Due to the constant emergence of new information about the properties of microorganisms, each next edition of the guide differs from the previous one.

All living organisms are divided into the following groups: prokaryotes, eukaryotes and viruses .

Viruses have a non-cellular structure.

prokaryotes(Greek |. - about | - to | to |, cariope | - core) - do not have a formalized
nucleus|, the genetic material (DNA) is not surrounded by a nuclear membrane in them and
located| right in the cytoplasm. Prokaryotes include bacteria and cyanobacteria (blue-green algae).

eukaryotes(Greek |. - ei | - real | genuine |, true, cariope | - core) - have real | nucleus, the genetic material is surrounded by a nuclear membrane - a double membrane. Eukaryotes include fungi, algae, protozoa, plants and animals.

According to the new Code of Nomenclature of Bacteria, the following classification categories of the kingdom Procaryotae are distinguished: department - Class - Order - Family - Genus - species.

In the eighth edition (1974) of Bergi's Guide to the Definition of Bacteria, all microorganisms are grouped into the kingdom of prokaryotes ( Procaryotae), which includes two divisions - cyanobacteria and bacteria (Appendix 1).

In the ninth (1984) edition of Bergi's Guide to Bacteria Identification, all microorganisms are divided into 4 departments and united in the kingdom Procaryotae.

1. Department of Graciculitis (Gracilicutes) (i.e. thin-walled, Gram-negative bacteria) (classes Scotobacteria, Anoxyphotobacteria, Oxyphotobacteria) combines gram-negative, polymorphic, spore-free microorganisms, in which peptidoglycan (murein) is included in the rigid cell wall. Top elastic
wall contains an outer membrane covered with a layer of protein
and glycoprotein. There is a periplasmic space between the cell wall and the cytoplasmic membrane of the Gracilicut.

2. Department of Fermicuta (Firmicutes) (i.e. thick-walled, Gram-positive bacteria) (classes Firmibacteria, Tallobacteria) combines gram-positive rod-shaped, spherical and filamentous microorganisms. Among them are aerobes, anaerobes and facultative anaerobes. Mobile and immobile forms that form endo- and exospores.

3. Department of tenerikuta (Tenericutes) (Class Mollicutes). Mollicutes are polymorphic prokaryotes that do not synthesize peptidoglycan and therefore do not form a cell wall. The function of the wall is performed by a strong three-layer cytoplasmic membrane. Mollicutes are insensitive to penicillin. The collective name for these microorganisms is mycoplasmas.

4. Department of Mendozicuta (Mendosicutes) (Class Archaeobacteria) includes prokaryotes with an imperfect cell wall, which instead of murein contains pseudomurein, which lacks muramic
acid. Cells are shaped like cocci, rods and spirals, as well as pyramids, squares, etc.


Similar information.


The name of microorganisms is assigned in accordance with the rules of the International Code of Nomenclature for Bacteria D. Bergey (1984).

In microbiology, as in biology, a double (binary) nomenclature, proposed back in the 18th century by K. Linyaey, is adopted to designate the type of bacteria. The first word is capitalized latin letter and denotes a genus that characterizes any morphological or physiological trait or the name of the scientist who discovered this microbe. The second word - view - is written with lower case and is a derivative of a noun that describes the color of the colony, the source of origin of the microorganism, the process or disease caused by it, and some others features. For example, Escherichia coli indicates that the microbe discovered Escherich, coli - an inhabitant of the intestine; Bacillus anthracis - the microbe forms a spore, anthracis - the causative agent of anthrax. Azotobacter is a microorganism that fixes atmospheric nitrogen.

The main nomenclature unit is the species. VD Timakov (1973) gives it the following definition; “A species is a collection of microorganisms that have a common origin and genotype, are similar in morphological and biological properties, and have a hereditarily fixed ability to cause in the environment natural habitat qualitatively defined specific processes. The species is subdivided into subspecies or variants. When studying isolated bacteria, deviations from typical species properties are often found; such a culture is considered as a subspecies. There are also infrasubdivisions, which are based on the difference between individuals by some small hereditary trait: antigenic - serovar, biochemical - biovar, relation to phages - fagovar, pathogenicity - patovar, etc.

The introduction to the words of the general part "var" (variant) is recommended in order to avoid possible misunderstandings, the previously used term "type" is used to designate the name-bearing type.

In microbiology, the terms "strain" and "clone" are used. Strain - a culture of the same species, isolated from different objects and characterized by minor changes in properties (for example, sensitivity to antibiotics, fermentation of carbohydrates, etc.). The term "culture" refers to microorganisms grown on a solid or liquid nutrient medium in a laboratory. A clone is a culture derived from a single cell. A culture of microorganisms containing individuals of the same species is called a pure culture. A mixed culture is a suspension containing various types of microorganisms isolated from the material under study (milk, meat, soil, water).

In microbiology, there are two different approaches to taxonomy, leading to two types of classification. The first one is based on the idea of ​​creating a natural (phylogenetic) classification of prokaryotes, that is, building unified system, which objectively reflects the relationship between different groups and the history of their evolutionary development. The second approach to taxonomy pursues practical goals and serves to identify, that is, to establish the belonging of a microorganism to a particular species. This is an artificial classification (traditional). Modern systems classifications of microorganisms are essentially artificial. This is served by determinants, which are used mainly in the identification of a particular microorganism. Such determinants include: “Key to bacteria and actinomycetes” by N.L. Krasilnikov (1949), “Key to microbes” by RA. Zion (1948) and others. the ninth edition of which was published in 1997. In this guide, all prokaryotic microorganisms are grouped into the kingdom Procaryotae (Murray, 1968), which is subdivided into four divisions. They, in turn, are divided into sections, classes, orders, families, genera, species.


Control questions:

1. Principles of taxonomy of microorganisms

2. Phenotypic, genetic and serological criteria for taxonomy

3. Modern phylogenetic and phenotypic classification of bacteria

4. Characteristics of the departments of the kingdom Prokaryotae

1. Principles of taxonomy of microorganisms

    Systematics (= taxonomy) bacteria is one of the most important and complex, but less developed sections of microbiology.

    Tasks of taxonomy are the classification, nomenclature and identification of organisms.

    Classification– distribution of many organisms into groups (taxa).

    At present, two different approaches to taxonomy have been adopted in microbiology, which determine the presence of two classification systems: phylogenetic (natural) and phenotypic (artificial).

    The basis phylogeneticclassification the idea of ​​creating a system of prokaryotes that objectively reflects the relationship between different groups of bacteria and the history of their evolutionary development was put forward.

    Phenotypicclassification pursues, first of all, practical goals, which are to quickly establish the belonging of a microorganism to a particular taxon. There is no generally accepted classification scheme for bacteria, but the most popular and widely used is the one given in Burgey's Bacteria Key. The first edition was published in 1923, the last (9th) - in 1994. Bacteria are described by groups (35 groups), which include families, genera, and species.

    Nomenclature a - naming individual groups and types of microorganisms. In the taxonomy of bacteria, as well as in botany, zoology, it is accepted binary nomenclature , according to which a name is assigned to bacteria, consisting of two words: the first determines their belonging to a particular genus, the second - to a species. For example, Clostridium botulinum And Clostridium tetani- two different kind bacteria that belong to the same genus. Bacteria are named according to the rules of the International Code of Nomenclature for Bacteria.

    View is the main taxonomic category . In microbiology under view usually understand the type strain and all other strains that are considered sufficiently similar to the type strain.

    Type strain is a strain chosen as a permanent specimen of what is meant by the species. Cultures of type strains are found in various collections (eg American Type Culture Collection).

    Species are grouped into genera, genera into families, families into orders, followed by classes, divisions, and kingdoms. In microbiology, there are also smaller taxonomic units than species: subspecies ( subspecies), variety. Subspecies may differ in physiological (biovar), morphological (morphovar) or antigenic (serovar) properties.

    Clone- a pure culture obtained from a single cell

    Wthere M- cultures of bacteria of the same species isolated from different sources or from one source in different time or obtained through genetic manipulation. Different strains of the same type of bacteria may differ from each other in a number of properties, for example, in sensitivity to antibiotics, the ability to synthesize toxins, enzymes, etc.

    Identification - establishes the belonging of microorganisms to a particular taxon based on the presence of specific characters. In most cases, identification consists in determining the genus and species of microorganisms.

    When identifying microorganisms, certain rules should be followed:

Be sure of the purity of the selected culture;

Testing for the study of physiological and biochemical characteristics should be carried out at least twice;

It is obligatory to set a known positive and a known negative control.

    The researcher must find out whether the organism is phototrophic, chemoautotrophic, or chemoheterotrophic. It is also necessary to know whether it is an aerobe, anaerobe, microaerophile or facultative anaerobe, as well as to determine some morphological properties, Gram stain, cell shape, specific morphological features (presence of spores, capsules, etc.). Three physiological tests are very important: for the presence of catalase, the presence of oxidase, and the ability to aerobic or anaerobic carbohydrate catabolism.

    When classifying bacteria, a large number of different properties and characteristics are taken into account.

    Systematics criteria are properties and characteristics characteristic of all bacteria of a given group and uncharacteristic of microorganisms of other groups. The more common features the compared organisms have, the more grounds there are for including them in one taxonomic group.

It is customary to consider unicellular organisms, the size of which does not exceed 0.1 mm. Representatives of this large group may have different cellular organization, morphological features and metabolic capabilities, that is, the main feature that unites them is size. The term "microorganism" itself is not endowed with a taxonomic sense. Microbes belong to a variety of taxonomic units, and other representatives of these units can be multicellular and reach large sizes.

General approaches to the classification of microorganisms

As a result of the gradual accumulation of factual material about microbes, it became necessary to introduce rules for their description and systematization.

The classification of microorganisms is characterized by the presence of the following taxa: domain, phylum, class, order, family, genus, species. In microbiology, scientists use the binomial system of object characteristics, that is, the nomenclature includes the names of the genus and species.

Most microorganisms are characterized by an extremely primitive and universal structure, therefore, their division into taxa cannot be carried out only according to morphological features. Functional features, molecular biological data, and schemes of the flow of biochemical processes, etc. are used as criteria.

Features of identification

To identify an unknown microorganism, studies are carried out to study the following properties:

  1. Cytology of cells (primarily belonging to pro- or eukaryotic organisms).
  2. Morphology of cells and colonies (under specific conditions).
  3. Cultural characteristics (features of growth on different media).
  4. The complex of physiological properties on which the classification of microorganisms by type of respiration is based (aerobic, anaerobic)
  5. Biochemical signs (presence or absence of certain metabolic pathways).
  6. A set of molecular biological properties, including taking into account the nucleotide sequence, the possibility of hybridization of nucleic acids with the material of typical strains.
  7. Chemotaxonomic indicators, implying taking into account the chemical composition of various compounds and structures.
  8. Serological characteristics (reactions "antigen - antibody"; especially for pathogenic microorganisms).
  9. The presence and nature of sensitivity to specific phages.

The systematics and classification of microorganisms related to prokaryotes is carried out using the Bergey's Guide to the Systematics of Bacteria. And the identification is carried out using the Burgey determinant.

Various ways to classify microbes

To determine the taxonomic affiliation of an organism, several methods of classifying microorganisms are used.

With a formal numerical classification, all features are considered equally significant. That is, the presence or absence of a particular feature is taken into account.

Morphophysiological classification involves the study of the totality of morphological properties and features of the course of metabolic processes. In this case, it is endowed with meaning and significance of a particular property of an object. The placement of a microorganism in one or another and the assignment of a name depend primarily on the type of cellular organization, the morphology of cells and colonies, as well as the nature of growth.

Accounting for functional characteristics provides for the possibility of using various nutrients by microorganisms. Also important is the dependence on certain physical and chemical factors of the environment, and in particular the ways of obtaining energy. There are microbes that require chemotaxonomic studies to identify them. Pathogenic microorganisms require serodiagnosis. A qualifier is used to interpret the results of the above tests.

In molecular genetic classification, the structure of the molecules of the most important biopolymers is analyzed.

Order of identification of microorganisms

Nowadays, the identification of a specific microscopic organism begins with the isolation of its pure culture and analysis of the 16S rRNA nucleotide sequence. Thus, the place of the microbe on the phylogenetic tree is determined, and the subsequent specification by genus and species is carried out using traditional microbiological methods. The coincidence value equal to 90% allows you to determine the generic affiliation, and 97% - species.

An even clearer differentiation of microorganisms by genus and species is possible using polyphyletic (polyphase) taxonomy, when the determination of nucleotide sequences is combined with the use of information at various levels, up to ecological. That is, a search for groups of similar strains is carried out first, followed by determining the phylogenetic positions of these groups, fixing the differences between the groups and their nearest neighbors, and collecting data to differentiate the groups.

The main groups of eukaryotic microorganisms: algae

This domain includes three groups where there are microscopic organisms. We are talking about algae, protozoa and fungi.

Algae are unicellular, colonial or multicellular phototrophs that carry out oxygenic photosynthesis. The development of a molecular genetic classification of microorganisms belonging to this group has not yet been completed. Therefore, on this moment in practice, the classification of algae is used based on the composition of pigments and reserve substances, the structure of the cell wall, the presence of mobility and the method of reproduction.

Typical representatives of this group are unicellular organisms belonging to dinoflagellates, diatoms, euglenoids and green algae. All algae are characterized by the formation of chlorophyll and various forms carotenoids, but the ability to synthesize other forms of chlorophylls and phycobilins in the representatives of the group manifests itself in different ways.

The combination of these or those pigments causes the staining of cells in different colors. They can be green, brown, red, golden. Cell pigmentation is a species characteristic.

Diatoms are unicellular planktonic forms that have the appearance of a silicon bivalve shell. Some representatives are capable of movement by the type of sliding. Reproduction is both asexual and sexual.

The habitats of unicellular organisms are freshwater reservoirs. They move with the help of flagella. There is no cell wall. Able to grow in the dark due to the process of oxidation of organic substances.

Dinoflagellates have a special structure of the cell wall, it consists of cellulose. These planktonic unicellular algae have two lateral flagella.

For microscopic representatives, habitats are fresh and marine water bodies, soil and the surface of various terrestrial objects. There are non-motile species, and some are capable of locomotion using flagella. Just like dinoflagellates, green microalgae have a cellulose cell wall. The storage of starch in cells is characteristic. Reproduction is carried out both asexually and sexually.

eukaryotic organisms: protozoa

The basic principles for the classification of microorganisms belonging to the protozoa are based on morphological characteristics that vary greatly among representatives of this group.

They can lead a stationary lifestyle or move around with the help of various devices: flagella, cilia and pseudopods. Within the taxonomic group of protozoa, there are several more groups.

Representatives of the simplest

Amoebas carry out nutrition by endocytosis, move with the help of pseudopods, the essence of reproduction lies in the primitive in two. Most amoebas are free-living aquatic forms, but there are also those that cause diseases in humans and animals.

Infusoria cells have two different nuclei, asexual reproduction is in transverse division. There are representatives who are characterized sexual reproduction. A coordinated system of cilia takes part in the movement. Endocytosis is carried out by capturing food in a special oral cavity, and the remains are excreted through an opening at the posterior end. In nature, ciliates live in polluted organic matter reservoirs, as well as the rumen of ruminants.

Flagellates are characterized by the presence of flagella. The absorption of dissolved nutrients is carried out by the entire surface of the CPM. Division occurs only in the longitudinal direction. Among flagellates, there are both free-living and symbiotic species. The main symbionts of humans and animals are trypanosomes (cause sleeping sickness), leishmania (cause difficult-to-heal ulcers), giardia (lead to intestinal disorders).

In sporozoans, of all the protozoa, the most complex life cycle. Most famous representative sporozoans - malarial plasmodium.

eukaryotic microorganisms: fungi

The classification of microorganisms according to classifies representatives of this group as heterotrophs. Most are characterized by the formation of mycelium. Respiration is usually aerobic. But there are also facultative anaerobes that can switch to alcoholic fermentation. Reproduction methods are vegetative, asexual and sexual. It is this feature that serves as a criterion for further

If we talk about the importance of representatives of this group, then the combined non-taxonomic group of yeasts is of the greatest interest here. This includes mushrooms that do not have a mycelial growth stage. There are many facultative anaerobes among yeasts. However, there are also pathogenic species.

The main groups of microorganisms-prokaryotes: archaea

The morphology and classification of prokaryotic microorganisms unite them into two domains: bacteria and archaea, whose representatives have many significant differences. Archaea lack peptidoglycan (mureic) cell walls. They are characterized by the presence of another heteropolysaccharide - pseudomurein, in which there is no N-acetylmuramic acid.

Archaea are divided into three phyla.

Features of the structure of bacteria

The principles of classification of microorganisms that combine microbes into this domain are based on the structural features of the cell membrane, and in particular the content of peptidoglycan in it. At the moment there are 23 phylums in the domain.

Bacteria are an important link in the cycle of substances in nature. The essence of their significance in this global process is the decomposition of plant and animal residues, the purification of water bodies polluted with organic matter, and the modification of inorganic compounds. Without them, the existence of life on Earth would be impossible. These microorganisms live everywhere, their habitat can be soil, water, air, human body, animals and plants.

According to the shape of the cells, the presence of devices for movement, the articulation of cells among themselves, this domain is carried out within the subsequent classification of microorganisms. Microbiology considers the following types of bacteria based on the shape of the cells: round, rod-shaped, filamentous, convoluted, spiral. According to the type of movement, bacteria can be immobile, flagellated, or move due to the secretion of mucus. Based on the method of articulation of cells with each other, bacteria can be isolated, linked in the form of pairs, granules, and branching forms are also found.

Pathogenic microorganisms: classification

There are many pathogenic microorganisms among rod-shaped bacteria (causative agents of diphtheria, tuberculosis, typhoid fever, anthrax); protozoa (malarial plasmodium, toxoplasma, leishmania, giardia, trichomonas, some pathogenic amoeba), actinomycetes, mycobacteria (causative agents of tuberculosis, leprosy), molds and yeast-like fungi (causative agents of mycoses, candidiasis). Mushrooms can cause all sorts of skin lesions, for example different types depriving (with the exception of herpes zoster, in the appearance of which the virus is involved). Some yeasts, being permanent inhabitants of the skin, under conditions normal operation the immune system is not adversely affected. However, if the activity of immunity decreases, then they cause the appearance of seborrheic dermatitis.

Pathogenicity groups

The epidemiological danger of microorganisms is a criterion for combining all pathogenic microbes into four groups corresponding to four risk categories. Thus, the pathogenicity groups of microorganisms, the classification of which is given below, are of the greatest interest to microbiologists, since they directly affect the life and health of the population.

The safest, the 4th pathogenicity group, includes microbes that do not pose a threat to the health of an individual (or the risk of this threat is negligible). That is, the risk of infection is very small.

The 3rd group is characterized by a moderate risk of infection for an individual, a low risk for society as a whole. Such pathogens could theoretically cause disease, and even if they do, there are proven effective treatments, as well as a set of preventive measures that can prevent the spread of infection.

The 2nd pathogenicity group includes microorganisms that pose a high risk for the individual, but low for society as a whole. In this case, the pathogen can cause severe disease in humans, but it does not spread from one infected person to another. Effective Methods treatment and prevention are available.

The 1st pathogenicity group is characterized by a high risk for both the individual and society as a whole. A pathogen that causes severe disease in humans or animals can be easily transmitted different ways. Effective treatments and preventive measures usually absent.

Pathogenic microorganisms, the classification of which determines their belonging to one or another pathogenicity group, cause great damage to the health of society only if they belong to the 1st or 2nd group.