General microbiology. Microbiology What does the science of microbiology study?

And 26 more file(s).
Show all linked files

1. 
   Microbiology as a science. Objectives and research methods in microbiology.

Microbiology subject – microorganisms, their morphology, physiology, genetics, taxonomy, ecology and relationships with other life forms. For medical microbiology – pathogenic and opportunistic microorganisms.

Microorganisms - the most ancient form of organization of life on Earth, they appeared long before the emergence of plants and animals - approximately 3-4 billion years ago.

Objectives of microbiology:

Objectives of medical microbiology:

1. Study of the biology of pathogenic (disease-causing) and normal microbes for humans.

2. Study of the role of microbes in the occurrence and development of infectious (contagious) diseases and the formation of the immune response of the macroorganism (“host”).

3. Development of methods for microbiological diagnostics, specific treatment and prevention of human infectious diseases.

Research methods in microbiology:

1. 
   Microscopic- study of the morphology of microbes in a stained and unstained state using various types of microscopes.
2. 
   Microbiological(bacteriological, mycological, virological). The method is based on the isolation of a pure culture of the pathogen and its subsequent identification.
3. 
   Chemical
4. 
   Experimental (biological)- contamination of laboratory animals with microbes.
5. 
   Immunological(in the diagnosis of infections) - the study of specific responses of the macroorganism to contact with microbes.

1. 
   Main periods in the development of microbiology and immunology.

1. 
   Initial period

1. 
   Pasteur period

• 
  fermentation
• 
  the role of microbes in the cycle of substances in nature and spontaneous generation.

Next to the name Pasteur the name came up Robert Koch, an outstanding master of applied research, he discovered the causative agent of anthrax, cholera, tuberculosis and other microorganisms.

1. 
   Third period

1. 
   Modern period.

3. Founders of microbiology.

L. Pasteur

1. 
   study of the microbiological basis of fermentation and decay processes,
2. 
   development of industrial microbiology,
3. 
   elucidation of the role of microorganisms in the circulation of substances in nature,
4. 
   discovery of anaerobic microorganisms,
5. 
   development of asepsis principles,
6. 
   development of sterilization methods,
7. 
   weakening (attenuation) of virulence. The degree of pathogenicity is virulence. Thus, if you weaken the virulence, you can get a vaccine.
8. 
   receiving vaccines (vaccine strains) – cholera and rabies.
9. 
   Pasteur holds the honor of discovering staphylococci and streptococci

R. Koch - German naturalist, student of Pasteur.

4. The role of domestic scientists in the development of microbiology.

1. 
   Tsenkovsky L.S.. organized the production of anthrax vaccine, and in 1883 successfully used it to vaccinate livestock.
2. 
   Minh. He proved that the spirochete of relapsing fever is the causative agent of the disease.
3. 
   Mochutkovsky self-infected himself with typhus (injected the patient’s blood), proving that the pathogen was present in the patient’s blood.
4. 
   Lesha F.A. Proved that dysentery can be caused by protozoa belonging to amoebas.
5. 
   Played a great role in microbiology I.I. Mechnikov. He was the creator of the phagocytic theory of immunity. Then he publishes the work “Immunity to Infectious Diseases.”
6. 
   In 1886, the first bacteriological station was opened in Odessa, headed by Mechnikov and his assistants Gamel N.F. and Barlah L.V.
7. 
   Next, a station was opened in Kharkov. Was in charge Vinogradsky. He worked in the field of general microbiology. He discovered sulfur and iron bacteria, nitrifying bacteria - the causative agents of nitrification in the soil.
8. 
   DI. Ivanovsky(discovered the tobacco mosaic virus, considered the founder of virology).
9. 
   Tsinkovsky (participated in the development of anthrax vaccination methods).
10. 
    Amilyansky- wrote the first textbook “Fundamentals of Microbiology”, discovered the causative agent of cellulose fermentation, studied nitrogen-fixing bacteria.
11. 
    Mikhin- laid the foundation for veterinary microbiology, discovered the causative agent of leptospirosis.
12. 
    Shaposhnikov– founder of technical microbiology.
13. 
    Voitkevich– worked with acidophilus bacillus, considered the founder of therapeutic and dietary nutrition for animals.

Since the mid-20th century, microbiology as a discipline has been included in the undergraduate curriculum.

5. Basics of taxonomy and nomenclature of microorganisms.

According to modern taxonomy, microorganisms belong to 3 kingdoms:

I. Prokaryotes:
* Eubacteria
1. Gracilicutes (thin cell wall)
2. Firmicutes (thick cell wall)
3. Tenericutes (no cell wall)
Spirochetes, rickettsia, chlamydia, mycoplasmas, actinomycetes.
* Archaebacteria
4. Mendocutes
II. Eukaryotes: Animals Plants Mushrooms Protozoa
III. Non-cellular life forms: Viruses Prions Plasmids

Species – Genus – Family – Order – Class – Division – Kingdom.

The designation of microorganisms includes the name of the genus and species. Genus with a capital letter, type with a small letter. Generic name by the author's surname or bacterial morphology. Species name – according to clinical signs, colony morphology, habitat.

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

1. Numeric taxonomy . Recognizes the equivalence of all characteristics. To use it, you need to have information about many dozens of signs. Species affiliation is determined by the number of matching characteristics.

2. Serotaxonomy. Studies bacterial antigens using reactions with immune sera. Most often used in medical bacteriology. Disadvantage: bacteria do not always contain species-specific antigen.

3. Chemotaxonomy. Physicochemical methods are used to study the lipid and amino acid composition of the microbial cell and certain of its components.

4. Gene systematics. It is based on the ability of bacteria with homologous DNA to transform, transduce and conjugate, on the analysis of extrachromosomal factors of heredity - plasmids, transposons, phages. Geographical location of detection.

Specialized terms:

View - an evolutionarily established set of individuals having a single genotype, manifested by similar phenotypic characteristics.

Option - individuals of the same species, differing in different characteristics (serovars, chemovars, cultivars, morphovars, phagovars).

Population – a collection of individuals of the same species that live in a certain territory for a relatively long time.

Culture – a collection of bacteria of one species (pure) or several species (mixed), grown on a nutrient medium (liquid or solid).

Strain – a pure culture of one type of bacteria, isolated at a certain time from one source.

The colony - a visible accumulation of bacteria of the same species on the surface or in the depths of a dense nutrient medium.

Clone – a cell culture grown from a single microorganism by cloning.

Microbiology studies the structure, vital 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 body of humans and animals. They can be useful and are used in many food products. They can be harmful, cause illness in people, spoilage of 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 provided magnification of 200 times or more. The microcosm he saw amazed him; Leeuwenhoek described and sketched the microorganisms he discovered 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 shape and structure, but also in their vital functions. Pasteur established that yeast causes alcoholic fermentation, and some microbes can cause infectious diseases in humans and animals. Pasteur went down in history as the inventor of the vaccination method against rabies and anthrax. The world famous contribution to microbiology is R. Koch (1843-1910) - he discovered the causative agents of tuberculosis and cholera, I. I. Mechnikova (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 tiny, mostly single-celled 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, differing in structure, properties, and ability to exist in different environmental conditions. They can be unicellular, multicellular And non-cellular.

Microbes are divided into bacteria, viruses and phages, fungi, and yeast. Separately, there are varieties of bacteria - rickettsia, mycoplasma, and a special group consists 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 (bacillus, etc.), convoluted (vibrios, spirochetes, spirilla) (Fig. 1).

Globular bacteria (cocci) They are usually spherical in shape, but can 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), in a package (sarcins). Streptococci can cause tonsillitis and erysipelas, while staphylococci can cause various inflammatory and purulent processes.

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

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

Sporulation is a complex process. Spores are significantly different from an ordinary 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 remain 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.

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

bacterial cell has a cell wall (sheath), often covered with mucus. Often the mucus forms a capsule. The contents of the cell (cytoplasm) are separated from the membrane by the cell membrane. 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.).

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

Some bacteria can move. 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, and can be located over the entire surface of the bacterium. Many rod-shaped bacteria and almost all curved bacteria have flagella. Spherical bacteria, as a rule, do not have flagella and are immobile.

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

Viruses

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

Viruses cause such common human diseases as influenza, 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 everywhere where there are microorganisms. Phages cause the death of microbial cells and can be used to treat and prevent certain infectious diseases.

Mushrooms are special plant organisms that do not have chlorophyll and do not synthesize organic substances, but require ready-made organic substances. Therefore, fungi develop on various substrates containing nutrients. Some fungi can cause 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 take the form of long and branching or intertwining threads - hyphae. Formed from hyphae mycelium, or mycelium. Mycelium can consist of cells with one or several nuclei or be noncellular, 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 different ways, including vegetatively as a result of hyphal division. Most fungi reproduce asexually and sexually through the formation of special reproduction cells - dispute. Spores, as a rule, are able to persist for a long time in the external environment. Mature spores can be transported over considerable distances. Once in the nutrient medium, the spores quickly develop into hyphae.

A large group of fungi are represented by molds (Fig. 2). Widely distributed in nature, they can grow on food products, forming clearly visible plaques of different colors. Food spoilage is often caused by mucor fungi, which form a fluffy white or gray mass. The mucor 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 of products can be fungi of the genus Peniillium.

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

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

Actinomycetes- microorganisms that have characteristics of both bacteria and fungi. In structure and biochemical properties, actinomycetes are similar to bacteria, and in terms of the nature of reproduction and the ability to form hyphae and mycelium, they are similar to mushrooms.

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

Yeast

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

Yeasts are widespread in nature, they can be found in soil and on plants, on food products and various industrial wastes 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 industries.

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

Microbiology is a science whose subject of study is microscopic creatures called microorganisms, their biological characteristics, taxonomy, ecology, and relationships with other organisms.

Microorganisms are the most ancient form of organization of life on Earth. In terms of quantity, they represent the most significant and most diverse part of the organisms inhabiting the biosphere.

Microorganisms include:

1) bacteria;

2) viruses;

4) protozoa;

5) microalgae.

A common feature of microorganisms is microscopic size; They differ in structure, origin, and physiology.

Bacteria are single-celled microorganisms of plant origin, lacking chlorophyll and lacking a nucleus.

Fungi are unicellular and multicellular microorganisms of plant origin, lacking chlorophyll, but having the features of an animal cell, eukaryote.

Viruses are unique microorganisms that do not have a cellular structural organization.

Main sections of microbiology: general, technical, agricultural, veterinary, medical, sanitary.

General microbiology studies the most general patterns inherent in each group of listed microorganisms: structure, metabolism, genetics, ecology, etc.

The main task of technical microbiology is the development of biotechnology for the synthesis by microorganisms of biologically active substances: proteins, enzymes, vitamins, alcohols, organic substances, antibiotics, etc.

Agricultural microbiology deals with the study of microorganisms that participate in the cycle of substances, are used to prepare fertilizers, cause plant diseases, etc.

Veterinary microbiology studies pathogens of animal diseases, develops methods for their biological diagnosis, specific prevention and etiotropic treatment aimed at destroying pathogenic microbes in the body of a sick animal.

The subject of study of medical microbiology is pathogenic (pathogenic) and conditionally pathogenic microorganisms for humans, as well as the development of methods for microbiological diagnosis, specific prevention and etiotropic treatment of infectious diseases caused by them.

A branch of medical microbiology is immunology, which studies the specific mechanisms of protection of human and animal organisms from pathogens.

The subject of study of sanitary microbiology is the sanitary and microbiological state of environmental objects and food products, the development of sanitary standards.

The basic taxonomic unit of bacterial taxonomy is the species.

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

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

1) serovars (by antigenic structure);

2) chemovars (according to sensitivity to chemicals);

3) phage products (based on sensitivity to phages);

4) fermenters;

5) bacteriocinovars;

6) bacteriocinogenovars.

Bacteriocins are substances produced by bacteria and have a detrimental effect on other bacteria. Bacteriocinovars are distinguished according to the type of bacteriocin produced, and bactericinogenovars are distinguished according to sensitivity.

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

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

2) tinctorial (the ability to be stained with various dyes);

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

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

5) antigenic.

Species related by genetic kinship are united into genera, genera into families, and families into orders. Higher taxonomic categories are classes, divisions, subkingdoms and kingdoms.

According to modern taxonomy, pathogenic microorganisms belong to the kingdom of prokaryotes, pathogenic protozoa and fungi - to the kingdom of eukaryotes, viruses are united in a separate kingdom - Vira.

All prokaryotes, which have a single type of cell organization, are combined into one department - Bacteria. However, their individual groups differ in structural and physiological characteristics. On this basis, the following are distinguished:

1) bacteria themselves;

2) actinomycetes;

3) spirochetes;

4) rickettsia;

5) chlamydia;

6) mycoplasma.

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

1. Numerical taxonomy. Recognizes the equivalence of all characteristics. To use it, you need to have information about many dozens of signs. Species affiliation is determined by the number of matching characteristics.

2. Serotaxonomy. Studies bacterial antigens using reactions with immune sera. Most often used in medical bacteriology. Disadvantage: bacteria do not always contain species-specific antigen.

3. Chemotaxonomy. Physicochemical methods are used to study the lipid and amino acid composition of the microbial cell and certain of its components.

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

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

For the cultivation of bacteria, nutrient media are used, which have a number of requirements.

1. Nutritional value. The bacteria must contain all the necessary nutrients.

2. Isotonicity. Bacteria must contain a set of salts to maintain osmotic pressure, a certain concentration of sodium chloride.

3. Optimal pH (acidity) of the environment. The acidity of the environment ensures the functioning of bacterial enzymes; for most bacteria it is 7.2–7.6.

4. Optimal electronic potential, indicating the content of dissolved oxygen in the medium. It should be high for aerobes and low for anaerobes.

5. Transparency (so that bacterial growth is visible, especially for liquid media).

6. Sterility (so that there are no other bacteria).

Classification of culture media

1. By origin:

1) natural (milk, gelatin, potatoes, etc.);

2) artificial - media prepared from specially prepared natural components (peptone, aminopeptide, yeast extract, etc.);

3) synthetic - media of known composition, prepared from chemically pure inorganic and organic compounds (salts, amino acids, carbohydrates, etc.).

2. By composition:

1) simple - meat-extract agar, meat-extract broth, Hottinger agar, etc.;

2) complex - these are simple ones with the addition of an additional nutrient component (blood, chocolate agar): sugar broth, bile broth, whey agar, yolk-salt agar, Kitt-Tarozzi medium, Wilson-Blair medium, etc.

3. By consistency:

1) solid (contain 3–5% agar-agar);

2) semi-liquid (0.15-0.7% agar-agar);

3) liquid (do not contain agar-agar).

4. By purpose:

1) general purpose – for cultivating most bacteria (meat agar, meat agar, blood agar);

2) special purpose:

a) selective - media on which bacteria of only one species (genus) grow, and the genus of others is suppressed (alkaline broth, 1% peptone water, yolk-salt agar, casein-charcoal agar, etc.);

b) differential diagnostic - media on which the growth of some types of bacteria differs from the growth of other species in certain properties, often biochemical (Endo, Levin, Gis, Ploskirev, etc.);

c) enrichment environments - environments in which the reproduction and accumulation of pathogenic bacteria of any kind or type occurs, i.e., enrichment of the material under study with them (selenite broth).

To obtain a pure culture, it is necessary to master the methods of isolating pure cultures.

Methods for isolating pure cultures.

1. Mechanical separation on the surface of a solid nutrient medium (stroke method by firing a loop, method of dilutions in agar, distribution over the surface of a solid nutrient medium with a spatula, Drigalsky method).

2. Use of elective nutrient media.

3. Creation of conditions favorable for the development of one species (genus) of bacteria (enrichment environment).

A pure culture is obtained in the form of colonies - this is an isolated accumulation of bacteria visible to the naked eye on a solid nutrient medium, which is usually the offspring of one cell.

Microbiological processes are widely used in various sectors of the national economy. They are based on the use in industry of biological systems and the processes caused by them. Many industries are based on metabolic reactions that occur during the growth and reproduction of certain microorganisms.

Currently, with the help of microorganisms, feed proteins, enzymes, vitamins, amino acids and antibiotics, organic acids, lipids, hormones, preparations for agriculture, etc. are produced.

In the food industry, microorganisms are used to produce a number of products. Thus, alcoholic drinks - wine, beer, cognac, spirits - and other products are produced using yeast. The baking industry uses yeast and bacteria, the dairy industry uses lactic acid bacteria, etc.

Among the variety of processes caused by microorganisms, one of the most important is fermentation.

Fermentation refers to the transformation of carbohydrates and some other organic compounds into new substances under the influence of enzymes produced by microorganisms. Various types of fermentation are known. They are usually named after the end products formed during the fermentation process, for example alcohol, lactic acid, acetic acid, etc.

Many types of fermentation - alcoholic, lactic acid, acetone butyl, acetic acid, citric acid and others, caused by various microorganisms - are used in industry. For example, yeast is used in the production of ethyl alcohol, bread, and beer; in the production of citric acid - molds; in the production of acetic and lactic acids, acetone¾ bacteria. The main goal of these industries is the transformation of the substrate (nutrient medium) under the influence of microorganism enzymes into the necessary products. In other industries, for example in the production of baker's yeast, the main task is to accumulate the maximum amount of cultivated yeast.

The main groups of microorganisms used in the food industry are bacteria, yeast and molds.

Bacteria. They use lactic acid, acetic acid, butyric acid as pathogens. acetone-butyl fermentation. Cultured lactic acid bacteria are used in the production of lactic acid, in baking, and sometimes in alcohol production. They convert sugar into lactic acid.

Lactic acid bacteria play an important role in the production of rye bread. In the process of producing rye bread, true (homofermentative) and non-true (heterofermentative) lactic acid bacteria are involved. Heterofermentative lactic acid bacteria, along with lactic acid, produce volatile acids (mainly acetic acid), alcohol and carbon dioxide. True bacteria in rye dough are involved only in acid formation, while non-true bacteria, along with acid formation, have a significant effect on the loosening of the dough, being energetic gas formers. Lactic acid bacteria in rye dough also have a significant impact on the taste of bread, since it depends on the total amount of acids contained in the bread and on their ratio. In addition, lactic acid affects the formation process and structural and mechanical properties of rye dough.

Butyric acid fermentation, caused by butyric acid bacteria, is used to produce butyric acid, the esters of which are used as aromatic substances, and for alcohol production these bacteria are dangerous, since butyric acid inhibits the development of yeast and inactivates a-amylase.

Special types of butyric acid bacteria include acetone-butyl bacteria, which convert starch and other carbohydrates into acetone, butyl and ethyl alcohols. These bacteria are used as fermentation agents in acetone-butyl production.

Acetic acid bacteria are used to produce vinegar (acetic acid solution), as they are capable of oxidizing ethyl alcohol into acetic acid.

It should be noted that acetic acid fermentation is harmful for alcohol production. since it leads to a decrease in the yield of alcohol, and in brewing it deteriorates the quality of beer and causes its spoilage.

- (from micro... and biology), the science of microorganisms. Microorganisms (bacteria) were first observed and described by A. Leeuwenhoek in 1683, but as a science, microorganisms were formed in the 2nd half of the 19th century, Ch. arr. influenced by the works of L. Pasteur. He found that certain chemicals. Biological encyclopedic dictionary