Improbability theory: infant fecal bacteria as a new probiotic. Pasteur's microbial theory in biology

Bacteria are the most ancient group of organisms that currently exist on Earth. The first bacteria probably appeared more than 3.5 billion years ago and for almost a billion years were the only living creatures on our planet. Since these were the first representatives of wildlife, their body had a primitive structure.

Over time, their structure became more complex, but even today bacteria are considered the most primitive unicellular organisms. Interestingly, some bacteria still retain the primitive features of their ancient ancestors. This is observed in bacteria that live in hot sulfur springs and anoxic silts at the bottom of reservoirs.

Most bacteria are colorless. Only a few are colored purple or green. But the colonies of many bacteria have a bright color, which is due to the release of a colored substance into the environment or pigmentation of the cells.

The discoverer of the world of bacteria was Anthony Leeuwenhoek, a Dutch naturalist of the 17th century, who first created a perfect magnifying glass microscope that magnifies objects 160-270 times.

Bacteria are classified as prokaryotes and are separated into a separate kingdom - Bacteria.

body shape

Bacteria are numerous and diverse organisms. They differ in form.

bacterium name	Bacteria shape	Bacteria image
cocci		spherical
Bacillus		rod-shaped
Vibrio		curved comma
Spirillum		Spiral
streptococci		Chain of cocci
Staphylococci		Clusters of cocci
diplococci		Two round bacteria enclosed in one slimy capsule

Ways of transportation

Among bacteria there are mobile and immobile forms. The mobile ones move by means of wave-like contractions or with the help of flagella (twisted helical threads), which consist of a special flagellin protein. There may be one or more flagella. They are located in some bacteria at one end of the cell, in others - on two or over the entire surface.

But movement is also inherent in many other bacteria that do not have flagella. So, bacteria covered with mucus on the outside are capable of sliding movement.

Some water and soil bacteria without flagella have gas vacuoles in the cytoplasm. There can be 40-60 vacuoles in a cell. Each of them is filled with gas (presumably nitrogen). By regulating the amount of gas in vacuoles, aquatic bacteria can sink into the water column or rise to its surface, while soil bacteria can move in soil capillaries.

Habitat

Due to the simplicity of organization and unpretentiousness, bacteria are widely distributed in nature. Bacteria are found everywhere: in a drop of even the purest spring water, in grains of soil, in the air, on rocks, in polar snows, desert sands, on the ocean floor, in oil extracted from great depths, and even in hot spring water with a temperature of about 80ºС. They live on plants, fruits, in various animals and in humans in the intestines, mouth, limbs, and on the surface of the body.

Bacteria are the smallest and most numerous living things. Due to their small size, they easily penetrate into any cracks, crevices, pores. Very hardy and adapted to various conditions of existence. They tolerate drying, extreme cold, heating up to 90ºС, without losing viability.

There is practically no place on Earth where bacteria would not be found, but in different quantities. The living conditions of bacteria are varied. Some of them need air oxygen, others do not need it and are able to live in an oxygen-free environment.

In the air: bacteria rise to the upper atmosphere up to 30 km. and more.

Especially a lot of them in the soil. One gram of soil can contain hundreds of millions of bacteria.

In water: in the surface water layers of open reservoirs. Beneficial aquatic bacteria mineralize organic residues.

In living organisms: pathogenic bacteria enter the body from the external environment, but only under favorable conditions cause disease. Symbiotic live in the digestive organs, helping to break down and assimilate food, synthesize vitamins.

External structure

The bacterial cell is dressed in a special dense shell - the cell wall, which performs protective and supporting functions, and also gives the bacterium a permanent, characteristic shape. The cell wall of a bacterium resembles the shell of a plant cell. It is permeable: through it, nutrients freely pass into the cell, and metabolic products go out into the environment. Bacteria often develop an additional protective layer of mucus, a capsule, over the cell wall. The thickness of the capsule can be many times greater than the diameter of the cell itself, but it can be very small. The capsule is not an obligatory part of the cell, it is formed depending on the conditions in which the bacteria enter. It keeps bacteria from drying out.

On the surface of some bacteria there are long flagella (one, two or many) or short thin villi. The length of the flagella can be many times greater than the size of the body of the bacterium. Bacteria move with the help of flagella and villi.

Internal structure

Inside the bacterial cell is a dense immobile cytoplasm. It has a layered structure, there are no vacuoles, so various proteins (enzymes) and reserve nutrients are located in the very substance of the cytoplasm. Bacterial cells do not have a nucleus. In the central part of their cells, a substance carrying hereditary information is concentrated. Bacteria, - nucleic acid - DNA. But this substance is not framed in the nucleus.

The internal organization of a bacterial cell is complex and has its own specific features. The cytoplasm is separated from the cell wall by the cytoplasmic membrane. In the cytoplasm, the main substance, or matrix, ribosomes and a small number of membrane structures that perform a variety of functions (analogues of mitochondria, endoplasmic reticulum, Golgi apparatus) are distinguished. The cytoplasm of bacterial cells often contains granules of various shapes and sizes. The granules may be composed of compounds that serve as a source of energy and carbon. Droplets of fat are also found in the bacterial cell.

In the central part of the cell, the nuclear substance, DNA, is localized, not separated from the cytoplasm by a membrane. This is an analogue of the nucleus - the nucleoid. Nucleoid does not have a membrane, nucleolus and a set of chromosomes.

Nutrition methods

Bacteria have different ways of feeding. Among them are autotrophs and heterotrophs. Autotrophs are organisms that can independently form organic substances for their nutrition.

Plants need nitrogen, but they themselves cannot absorb nitrogen from the air. Some bacteria combine nitrogen molecules in the air with other molecules, resulting in substances available to plants.

These bacteria settle in the cells of young roots, which leads to the formation of thickenings on the roots, called nodules. Such nodules are formed on the roots of plants of the legume family and some other plants.

The roots provide the bacteria with carbohydrates, and the bacteria give the roots nitrogen-containing substances that can be taken up by the plant. Their relationship is mutually beneficial.

Plant roots secrete many organic substances (sugars, amino acids, and others) that bacteria feed on. Therefore, especially many bacteria settle in the soil layer surrounding the roots. These bacteria convert dead plant residues into substances available to the plant. This layer of soil is called the rhizosphere.

There are several hypotheses about the penetration of nodule bacteria into root tissues:

• through damage to the epidermal and cortical tissue;
• through root hairs;
• only through the young cell membrane;
• due to companion bacteria producing pectinolytic enzymes;
• due to the stimulation of the synthesis of B-indoleacetic acid from tryptophan, which is always present in the root secretions of plants.

The process of introduction of nodule bacteria into the root tissue consists of two phases:

• infection of the root hairs;
• nodule formation process.

In most cases, the invading cell actively multiplies, forms the so-called infection threads, and already in the form of such threads moves into the plant tissues. Nodule bacteria that have emerged from the infection thread continue to multiply in the host tissue.

Filled with rapidly multiplying cells of nodule bacteria, plant cells begin to intensively divide. The connection of a young nodule with the root of a leguminous plant is carried out thanks to vascular-fibrous bundles. During the period of functioning, the nodules are usually dense. By the time of the manifestation of optimal activity, the nodules acquire a pink color (due to the legoglobin pigment). Only those bacteria that contain legoglobin are capable of fixing nitrogen.

Nodule bacteria create tens and hundreds of kilograms of nitrogen fertilizers per hectare of soil.

Metabolism

Bacteria differ from each other in metabolism. For some, it goes with the participation of oxygen, for others - without its participation.

Most bacteria feed on ready-made organic substances. Only a few of them (blue-green, or cyanobacteria) are able to create organic substances from inorganic ones. They played an important role in the accumulation of oxygen in the Earth's atmosphere.

Bacteria absorb substances from the outside, tear their molecules apart, assemble their shell from these parts and replenish their contents (this is how they grow), and throw out unnecessary molecules. The shell and membrane of the bacterium allows it to absorb only the right substances.

If the shell and membrane of the bacterium were completely impermeable, no substances would enter the cell. If they were permeable to all substances, the contents of the cell would mix with the medium - the solution in which the bacterium lives. For the survival of bacteria, a shell is needed that allows the necessary substances to pass through, but not those that are not needed.

The bacterium absorbs the nutrients that are near it. What happens next? If it can move independently (by moving the flagellum or pushing the mucus back), then it moves until it finds the necessary substances.

If it cannot move, then it waits until diffusion (the ability of the molecules of one substance to penetrate into the thick of the molecules of another substance) brings the necessary molecules to it.

Bacteria, together with other groups of microorganisms, perform a huge chemical job. By transforming various compounds, they receive the energy and nutrients necessary for their vital activity. Metabolic processes, ways of obtaining energy and the need for materials to build the substances of their body in bacteria are diverse.

Other bacteria satisfy all the needs for carbon necessary for the synthesis of organic substances of the body at the expense of inorganic compounds. They are called autotrophs. Autotrophic bacteria are able to synthesize organic substances from inorganic ones. Among them are distinguished:

Chemosynthesis

The use of radiant energy is the most important, but not the only way to create organic matter from carbon dioxide and water. Bacteria are known that use not sunlight as an energy source for such synthesis, but the energy of chemical bonds occurring in the cells of organisms during the oxidation of certain inorganic compounds - hydrogen sulfide, sulfur, ammonia, hydrogen, nitric acid, ferrous compounds of iron and manganese. They use the organic matter formed using this chemical energy to build the cells of their body. Therefore, this process is called chemosynthesis.

The most important group of chemosynthetic microorganisms are nitrifying bacteria. These bacteria live in the soil and carry out the oxidation of ammonia, formed during the decay of organic residues, to nitric acid. The latter, reacts with mineral compounds of the soil, turns into salts of nitric acid. This process takes place in two phases.

Iron bacteria convert ferrous iron to oxide. The formed iron hydroxide settles and forms the so-called swamp iron ore.

Some microorganisms exist due to the oxidation of molecular hydrogen, thereby providing an autotrophic way of nutrition.

A characteristic feature of hydrogen bacteria is the ability to switch to a heterotrophic lifestyle when provided with organic compounds and in the absence of hydrogen.

Thus, chemoautotrophs are typical autotrophs, since they independently synthesize the necessary organic compounds from inorganic substances, and do not take them ready-made from other organisms, like heterotrophs. Chemoautotrophic bacteria differ from phototrophic plants in their complete independence from light as an energy source.

bacterial photosynthesis

Some pigment-containing sulfur bacteria (purple, green), containing specific pigments - bacteriochlorophylls, are able to absorb solar energy, with the help of which hydrogen sulfide is split in their organisms and gives hydrogen atoms to restore the corresponding compounds. This process has much in common with photosynthesis and differs only in that in purple and green bacteria, hydrogen sulfide (occasionally carboxylic acids) is a hydrogen donor, and in green plants it is water. In those and others, the splitting and transfer of hydrogen is carried out due to the energy of absorbed solar rays.

Such bacterial photosynthesis, which occurs without the release of oxygen, is called photoreduction. The photoreduction of carbon dioxide is associated with the transfer of hydrogen not from water, but from hydrogen sulfide:

6CO 2 + 12H 2 S + hv → C6H 12 O 6 + 12S \u003d 6H 2 O

The biological significance of chemosynthesis and bacterial photosynthesis on a planetary scale is relatively small. Only chemosynthetic bacteria play a significant role in the sulfur cycle in nature. Absorbed by green plants in the form of salts of sulfuric acid, sulfur is restored and becomes part of protein molecules. Further, during the destruction of dead plant and animal residues by putrefactive bacteria, sulfur is released in the form of hydrogen sulfide, which is oxidized by sulfur bacteria to free sulfur (or sulfuric acid), which forms sulfites available for plants in the soil. Chemo- and photoautotrophic bacteria are essential in the cycle of nitrogen and sulfur.

sporulation

Spores form inside the bacterial cell. In the process of spore formation, a bacterial cell undergoes a series of biochemical processes. The amount of free water in it decreases, enzymatic activity decreases. This ensures the resistance of spores to adverse environmental conditions (high temperature, high salt concentration, drying, etc.). Spore formation is characteristic of only a small group of bacteria.

Spores are not an essential stage in the life cycle of bacteria. Sporulation begins only with a lack of nutrients or the accumulation of metabolic products. Bacteria in the form of spores can remain dormant for a long time. Bacterial spores withstand prolonged boiling and very long freezing. When favorable conditions occur, the dispute germinates and becomes viable. Bacterial spores are adaptations for survival in adverse conditions.

reproduction

Bacteria reproduce by dividing one cell into two. Having reached a certain size, the bacterium divides into two identical bacteria. Then each of them begins to feed, grows, divides, and so on.

After elongation of the cell, a transverse septum is gradually formed, and then the daughter cells diverge; in many bacteria, under certain conditions, cells after division remain connected in characteristic groups. In this case, depending on the direction of the division plane and the number of divisions, different forms arise. Reproduction by budding occurs in bacteria as an exception.

Under favorable conditions, cell division in many bacteria occurs every 20-30 minutes. With such rapid reproduction, the offspring of one bacterium in 5 days is able to form a mass that can fill all the seas and oceans. A simple calculation shows that 72 generations (720,000,000,000,000,000,000 cells) can be formed per day. If translated into weight - 4720 tons. However, this does not happen in nature, since most bacteria quickly die under the influence of sunlight, drying, lack of food, heating up to 65-100ºС, as a result of the struggle between species, etc.

The bacterium (1), having absorbed enough food, increases in size (2) and begins to prepare for reproduction (cell division). Its DNA (in a bacterium, the DNA molecule is closed in a ring) doubles (the bacterium produces a copy of this molecule). Both DNA molecules (3.4) appear to be attached to the bacterial wall and, when elongated, the bacteria diverge to the sides (5.6). First, the nucleotide divides, then the cytoplasm.

After the divergence of two DNA molecules on bacteria, a constriction appears, which gradually divides the body of the bacterium into two parts, each of which contains a DNA molecule (7).

It happens (in hay bacillus), two bacteria stick together, and a bridge is formed between them (1,2).

DNA is transported from one bacterium to another via the jumper (3). Once in one bacterium, DNA molecules intertwine, stick together in some places (4), after which they exchange sections (5).

The role of bacteria in nature

Circulation

Bacteria are the most important link in the general circulation of substances in nature. Plants create complex organic substances from carbon dioxide, water and soil mineral salts. These substances return to the soil with dead fungi, plants and animal corpses. Bacteria decompose complex substances into simple ones, which are reused by plants.

Bacteria destroy the complex organic matter of dead plants and animal corpses, excretions of living organisms and various wastes. Feeding on these organic substances, saprophytic decay bacteria turn them into humus. These are the kind of orderlies of our planet. Thus, bacteria are actively involved in the cycle of substances in nature.

soil formation

Since bacteria are distributed almost everywhere and are found in huge numbers, they largely determine the various processes that occur in nature. In autumn, the leaves of trees and shrubs fall, the above-ground grass shoots die off, old branches fall off, and from time to time the trunks of old trees fall. All this gradually turns into humus. In 1 cm 3. The surface layer of forest soil contains hundreds of millions of saprophytic soil bacteria of several species. These bacteria convert humus into various minerals that can be absorbed from the soil by plant roots.

Some soil bacteria are able to absorb nitrogen from the air, using it in life processes. These nitrogen-fixing bacteria live on their own or take up residence in the roots of leguminous plants. Having penetrated into the roots of legumes, these bacteria cause the growth of root cells and the formation of nodules on them.

These bacteria release nitrogen compounds that plants use. Bacteria obtain carbohydrates and mineral salts from plants. Thus, there is a close relationship between the leguminous plant and nodule bacteria, which is useful for both one and the other organism. This phenomenon is called symbiosis.

Thanks to their symbiosis with nodule bacteria, legumes enrich the soil with nitrogen, helping to increase yields.

Distribution in nature

Microorganisms are ubiquitous. The only exceptions are the craters of active volcanoes and small areas in the epicenters of detonated atomic bombs. Neither the low temperatures of the Antarctic, nor the boiling jets of geysers, nor saturated salt solutions in salt pools, nor the strong insolation of mountain peaks, nor the harsh radiation of nuclear reactors interfere with the existence and development of microflora. All living beings constantly interact with microorganisms, being often not only their storages, but also distributors. Microorganisms are the natives of our planet, actively developing the most incredible natural substrates.

Soil microflora

The number of bacteria in the soil is extremely large - hundreds of millions and billions of individuals in 1 gram. They are much more abundant in soil than in water and air. The total number of bacteria in soils varies. The number of bacteria depends on the type of soil, their condition, the depth of the layers.

On the surface of soil particles, microorganisms are located in small microcolonies (20-100 cells each). Often they develop in the thicknesses of clots of organic matter, on living and dying plant roots, in thin capillaries and inside lumps.

Soil microflora is very diverse. Different physiological groups of bacteria are found here: putrefactive, nitrifying, nitrogen-fixing, sulfur bacteria, etc. among them there are aerobes and anaerobes, spore and non-spore forms. Microflora is one of the factors of soil formation.

The area of ​​development of microorganisms in the soil is the zone adjacent to the roots of living plants. It is called the rhizosphere, and the totality of microorganisms contained in it is called the rhizosphere microflora.

Microflora of reservoirs

Water is a natural environment where microorganisms grow in large numbers. Most of them enter the water from the soil. A factor that determines the number of bacteria in water, the presence of nutrients in it. The cleanest are the waters of artesian wells and springs. Open reservoirs and rivers are very rich in bacteria. The greatest number of bacteria is found in the surface layers of water, closer to the shore. With increasing distance from the coast and increasing depth, the number of bacteria decreases.

Pure water contains 100-200 bacteria per 1 ml, while contaminated water contains 100-300 thousand or more. There are many bacteria in the bottom silt, especially in the surface layer, where the bacteria form a film. There are a lot of sulfur and iron bacteria in this film, which oxidize hydrogen sulfide to sulfuric acid and thereby prevent fish from dying. There are more spore-bearing forms in the silt, while non-spore-bearing forms predominate in the water.

In terms of species composition, the water microflora is similar to the soil microflora, but specific forms are also found. Destroying various wastes that have fallen into the water, microorganisms gradually carry out the so-called biological purification of water.

Air microflora

Air microflora is less numerous than soil and water microflora. Bacteria rise into the air with dust, can stay there for a while, and then settle to the surface of the earth and die from lack of nutrition or under the influence of ultraviolet rays. The number of microorganisms in the air depends on the geographic area, location, season, dust pollution, etc. Each speck of dust is a carrier of microorganisms. Most bacteria in the air over industrial enterprises. The air in the countryside is cleaner. The cleanest air is over forests, mountains, snowy spaces. The upper layers of the air contain fewer germs. In the air microflora there are many pigmented and spore-bearing bacteria that are more resistant than others to ultraviolet rays.

Microflora of the human body

The body of a person, even a completely healthy one, is always a carrier of microflora. When the human body comes into contact with air and soil, a variety of microorganisms, including pathogens (tetanus bacilli, gas gangrene, etc.), settle on clothing and skin. The exposed parts of the human body are most frequently contaminated. E. coli, staphylococci are found on the hands. There are over 100 types of microbes in the oral cavity. The mouth, with its temperature, humidity, nutrient residues, is an excellent environment for the development of microorganisms.

The stomach has an acidic reaction, so the bulk of microorganisms in it die. Starting from the small intestine, the reaction becomes alkaline, i.e. favorable for microbes. The microflora in the large intestine is very diverse. Each adult excretes about 18 billion bacteria daily with excrement, i.e. more individuals than people on the globe.

Internal organs that are not connected to the external environment (brain, heart, liver, bladder, etc.) are usually free from microbes. Microbes enter these organs only during illness.

Bacteria in the cycling

Microorganisms in general and bacteria in particular play an important role in the biologically important cycles of matter on Earth, carrying out chemical transformations that are completely inaccessible to either plants or animals. Various stages of the cycle of elements are carried out by organisms of different types. The existence of each separate group of organisms depends on the chemical transformation of elements carried out by other groups.

nitrogen cycle

The cyclic transformation of nitrogenous compounds plays a paramount role in supplying the necessary forms of nitrogen to various biosphere organisms in terms of nutritional needs. Over 90% of total nitrogen fixation is due to the metabolic activity of certain bacteria.

The carbon cycle

The biological transformation of organic carbon into carbon dioxide, accompanied by the reduction of molecular oxygen, requires the joint metabolic activity of various microorganisms. Many aerobic bacteria carry out the complete oxidation of organic substances. Under aerobic conditions, organic compounds are initially broken down by fermentation, and organic fermentation end products are further oxidized by anaerobic respiration if inorganic hydrogen acceptors (nitrate, sulfate, or CO2) are present.

Sulfur cycle

For living organisms, sulfur is available mainly in the form of soluble sulfates or reduced organic sulfur compounds.

The iron cycle

Some fresh water reservoirs contain high concentrations of reduced iron salts. In such places, a specific bacterial microflora develops - iron bacteria, which oxidize reduced iron. They participate in the formation of marsh iron ores and water sources rich in iron salts.

Bacteria are the most ancient organisms, appearing about 3.5 billion years ago in the Archaean. For about 2.5 billion years, they dominated the Earth, forming the biosphere, and participated in the formation of an oxygen atmosphere.

Bacteria are one of the most simply arranged living organisms (except for viruses). They are believed to be the first organisms to appear on Earth.

Currently, more than 2.5 million species of living organisms have been described on Earth. However, the actual number of species on Earth is several times greater, since many types of microorganisms, insects, etc. are not taken into account. In addition, it is believed that the modern species composition is only about 5% of the species diversity of life during the period of its existence on Earth.
Systematics, classification and taxonomy serve to streamline such a variety of living organisms.

Systematics - a branch of biology that deals with the description, designation and classification of existing and extinct organisms by taxa.
Classification - the distribution of the entire set of living organisms according to a certain system of hierarchically subordinate groups - taxa.
Taxonomy - a section of systematics that develops the theoretical foundations of classification. A taxon is a group of organisms artificially isolated by man, related to one degree or another, and at the same time sufficiently isolated so that it can be assigned a certain taxonomic category of one or another rank.

In the modern classification, there is the following hierarchy of taxa:

• kingdom;
• department (type in animal taxonomy);
• Class;
• order (order in animal taxonomy);
• family;

In addition, intermediate taxa are distinguished: over- and sub-kingdoms, over- and subdivisions, over- and subclasses, etc.

The taxonomy of living organisms is constantly changing and updating. It currently looks like this:

• Non-cellular forms
• Kingdom Viruses
• Cell forms
• The kingdom of Prokaryota (Procariota):
• kingdom of bacteria Bacteria, Bacteriobionta),
• kingdom of Archaebacteria Archaebacteria, Archaebacteriobionta),
• kingdom Prokaryotic algae
• department Blue-green algae, or Cyanei ( Cyanobionta);
• department Prochlorophyte algae, or Prochlorophytes ( Prochlororhyta).
• Kingdom of Eukaryotes (Eycariota)
• plant kingdom ( Vegetabilia, Phitobiota or Plantae):
• subkingdom of Bagryanka ( Rhodobionta);
• sub-kingdom True algae ( Phycobionta);
• sub-kingdom Higher plants ( Embryobionta);
• Kingdom of Mushrooms Fungi, Mycobionta, Mycetalia or Mycota):
• subkingdom Lower fungi (unicellular) ( Myxobionta);
• subkingdom Higher fungi (multicellular) ( Mycobionta);
• animal kingdom ( Animalia, Zoobionta)
• subkingdom Protozoa, or Unicellular ( Protozoa, Protozoobionta);
• subkingdom Multicellular ( Metazoa, Metazoobionta).

A number of scientists single out one kingdom of Drobyanka in the super-kingdom of Prokaryotes, which includes three sub-kingdoms: Bacteria, Archaebacteria and Cyanobacteria.

Viruses, bacteria, fungi, lichens

Kingdom of viruses

Viruses exist in two forms: resting(extracellular), when their properties as living systems do not manifest themselves, and intracellular when viruses replicate. Simple viruses (for example, tobacco mosaic virus) consist of a nucleic acid molecule and a protein shell - capsid.

Some more complex viruses (influenza, herpes, etc.), in addition to capsid proteins and nucleic acids, may contain a lipoprotein membrane, carbohydrates, and a number of enzymes. Proteins protect the nucleic acid and determine the enzymatic and antigenic properties of viruses. The shape of the capsid can be rod-shaped, filiform, spherical, etc.

Depending on the nucleic acid present in the virus, RNA-containing and DNA-containing viruses are distinguished. Nucleic acid contains genetic information, usually about the structure of the proteins of the capsid. It can be linear or circular, in the form of single or double stranded DNA, single or double stranded RNA.

The virus that causes AIDS (Acquired Immune Deficiency Syndrome) infects the blood cells that provide immunity to the body. As a result, an AIDS patient can die from any infection. AIDS viruses can enter the human body during sexual intercourse, during injections or operations if sterilization conditions are not followed. Prevention of AIDS consists in avoiding casual sex, using condoms, and using disposable syringes.

bacteria

All prokaryotes belong to the same kingdom of Drobyanka. It contains bacteria and blue-green algae.

The structure and activity of bacteria.

Prokaryotic cells do not have a nucleus, the location of DNA in the cytoplasm is called a nucleoid, the only DNA molecule is closed in a ring and is not associated with proteins, cells are smaller than eukaryotic cells, the cell wall contains a glycopeptide - murein, a mucous layer is located on top of the cell wall, which performs a protective function, there are no membrane organelles (chloroplasts, mitochondria, endoplasmic reticulum, Golgi complex), their functions are performed by invaginations of the plasma membrane (mesosomes), ribosomes are small, microtubules are absent, therefore the cytoplasm is motionless, there are no centrioles and division spindle, cilia and flagella have a special structure. Cell division is carried out by constriction (there is no mitosis and meiosis). This is preceded by DNA replication, then the two copies diverge, carried along by the growing cell membrane.

There are three groups of bacteria: archaebacteria, eubacteria and cyanobacteria.

archaebacteria- the most ancient bacteria (methane-forming, etc., about 40 species are known in total). They have common structural features of prokaryotes, but differ significantly in a number of physiological and biochemical properties from eubacteria. eubacteria- true bacteria, a later form in evolutionary terms. Cyanobacteria (cyanoea, blue-green algae)- phototrophic prokaryotic organisms that carry out photosynthesis like higher plants and algae with the release of molecular oxygen.

The following groups of bacteria are distinguished according to the shape of the cells: spherical - cocci, rod-shaped - bacilli, arcuately curved - vibrios, spiral - spirilla and spirochetes. Many bacteria are capable of independent movement due to flagella or due to cell contraction. Bacteria are unicellular organisms. Some are able to form colonies, but the cells in them exist independently of each other.

Under unfavorable conditions, some bacteria are able to form spores due to the formation of a dense shell around the DNA molecule with a portion of the cytoplasm. Bacterial spores are not used for reproduction, as in plants and fungi, but to protect the body from the effects of adverse conditions (drought, heating, etc.).

In relation to oxygen, bacteria are divided into aerobes(requires oxygen) anaerobes(dying in the presence of oxygen) and optional forms.

According to the mode of nutrition, bacteria are divided into autotrophic(carbon dioxide is used as a carbon source) and heterotrophic(using organic matter). Autotrophic, in turn, are divided into phototrophs(use the energy of sunlight) and chemotrophs(use the energy of oxidation of inorganic substances). The phototrophs are cyanobacteria(blue-green algae), which carry out photosynthesis, like plants, with the release of oxygen, and green and purple bacteria which carry out photosynthesis without the release of oxygen. Chemotrophs oxidize inorganic substances ( nitrifying bacteria, nitrogen-fixing bacteria, iron bacteria, sulfur bacteria, etc.).

Reproduction of bacteria.

Bacteria reproduce asexually - cell division(prokaryotes do not have mitosis and meiosis) with the help of constrictions or partitions, less often by budding. These processes are preceded by the duplication of the circular DNA molecule.

In addition, bacteria are characterized by a sexual process - conjugation. When conjugated through a special channel formed between two cells, a DNA fragment of one cell is transferred to another cell, that is, the hereditary information contained in the DNA of both cells changes. Since the number of bacteria does not increase, for correctness, the concept of "sexual process" is used, but not "sexual reproduction".

The role of bacteria in nature and the importance for humans

Thanks to a very diverse metabolism, bacteria can exist in a variety of environmental conditions: in water, air, soil, and living organisms. The role of bacteria is great in the formation of oil, coal, peat, natural gas, in soil formation, in the cycles of nitrogen, phosphorus, sulfur and other elements in nature. Saprotrophic bacteria participate in the decomposition of organic remains of plants and animals and in their mineralization to CO 2 , H 2 O, H 2 S, NH 3 and other inorganic substances. Together with fungi, they are decomposers. Nodule bacteria(nitrogen-fixing) form a symbiosis with leguminous plants and are involved in the fixation of atmospheric nitrogen into mineral compounds available to plants. Plants themselves do not have this ability.

A person uses bacteria in microbiological synthesis, in sewage treatment plants, to obtain a number of drugs (streptomycin), in everyday life and in the food industry (obtaining fermented milk products, winemaking).

kingdom mushrooms

General characteristics of mushrooms. Mushrooms are isolated in a special kingdom, numbering about 100 thousand species.

Differences between mushrooms and plants:

• heterotrophic mode of nutrition
• storage nutrient glycogen
• the presence of chitin in the cell walls

Differences between mushrooms and animals:

• unlimited growth
• absorption of food by suction
• reproduction by spores
• the presence of a cell wall
• inability to actively move
• The structure of mushrooms is diverse - from unicellular forms to complex hat forms.

Lichens

The structure of lichens. Lichens number more than 20 thousand species. These are symbiotic organisms formed by a fungus and an algae. At the same time, lichens are a morphologically and physiologically integral organism. The body of the lichen consists of intertwined hyphae of the fungus, between which algae (green or blue-green) are located. Algae carry out the synthesis of organic substances, and fungi absorb water and mineral salts. Depending on body structure thallus ) distinguish three groups of lichens: scale , or cortical(thallus has the appearance of plaques or crusts, tightly growing together with the substrate); foliate (in the form of plates attached to the substrate with bunches of hyphae); bushy (in the form of stems or ribbons, usually branched and growing together with the substrate only at the base). Lichen growth is extremely slow - only a few millimeters per year.

Lichen reproduction carried out either sexually (due to the fungal component), or asexually (formation of spores or breaking off pieces of the thallus).
The meaning of lichens. Due to their "dual" nature, lichens are very hardy. This is due to the possibility of both autotrophic and heterotrophic nutrition, as well as the ability to fall into a state of suspended animation, in which the body is severely dehydrated. In this state, lichens can tolerate the action of various adverse environmental factors (severe overheating or hypothermia, the almost complete absence of moisture, etc.). Biological features allow lichens to populate the most unfavorable habitats. They are often pioneers in the settlement of a particular land area, destroy rocks and form the primary soil layer, which is then mastered by other organisms.
At the same time, lichens are very sensitive to environmental pollution by various chemicals, which allows them to be used as bioindicators environmental conditions.
Lichens are used to obtain medicines, litmus, tannins and dyes. Yagel (reindeer moss) is the main food for reindeer. Some peoples eat lichens for food. Since the growth of lichens is very slow, measures are needed to protect it: regulation of reindeer grazing, orderly movement of vehicles, etc.

THEORETICAL MATERIAL
KINGDOM OF BACTERIA (= c. prokaryotes).

These are unicellular microscopic organisms that do not have a well-formed nucleus. The most ancient organisms appeared more than 3 billion years ago. Distributed everywhere: most of all - in the soil, less - in water, even less - in the air. Many of them in living organisms

1. The structure of the cell:

The cell is covered by a plasma membrane followed by a cell wall murein).

Most have a mucous capsule that protects the cell from drying out and contains toxins;

There are no membrane organelles (their functions are performed by mesosomes - membrane invaginations)

There are ribosomes smaller than in eukaryotic cells;

- genetic apparatus - NUCLEOID- a circular DNA molecule that is not associated with proteins (performs the function of a chromosome;

In the cytoplasm there are plasmids - small DNA molecules that determine individual signs of bacteria.

The organelles of movement are flagella and cilia.

2. Forms of bacteria

spherical - cocci (streptococci, staphylococci)

rod-shaped - bacilli (potato stick, lactic acid bacteria)

spirally convoluted - spirilla and spirochetes (pale spirochete - the causative agent of syphilis)

in the form of a comma - vibrios (cholerae vibrio)

vital activity

• food:

1. autotrophs (form organic matter)		heterotrophs (feed on ready-made organic matter)
   phototrophs	chemotrophs	saprophytes		symbionts
   (using solar energy) * cyanobacteria (blue-green algae)	(use the energy of chemical bonds) bacteria *iron bacteria	Saprotrophs (feed on non-living organic matter) *lactic acid bacteria	(using organic host body substances * pathogenic bacteria	(live at the expense of other organisms, benefiting them) * nodule bacteria (live in symbiosis with leguminous plants), * Escherichia coli (synthesizes vitamins of group B, K)

• breath:

• reproduction: halving every 20 minutes
• sporulation- the formation of disputes. Spore - the part of the cell covered with a dense membrane. Meaning: transfer of adverse conditions (cold, drought).

The spore can be dormant for decades, carried by water and wind. She is not afraid of drying, cold, heat. The killer factor for spores is direct sunlight or artificial irradiation with ultraviolet rays (UVR). When it enters a favorable environment, a bacterium is quickly formed from the spore.

The value of bacteria:

1. benefit:

Link in the food chain (food for unicellular organisms)

Decay bacteria form humus

Soil bacteria convert humus into mineral salts

Nodule bacteria (on the roots of leguminous plants) convert air nitrogen into salts, which are absorbed by the roots in dissolved form.

Lactic acid bacteria are used in the dairy industry, forage ensiling

Sulfur deposits are formed by sulfur bacteria, iron ore deposits are formed by iron bacteria.

In biotechnology (insulin synthesis)

harm:

Spoil food, books in bookstores, hay in stacks

Pathogens cause diseases: typhus, cholera, diphtheria, tetanus, tuberculosis, tonsillitis, anthrax, brucellosis, plague, botulism, whooping cough, venereal diseases

6. Ways to fight bacteria:

a) UFL processing;

b) hot steam treatment;

c) sterilization (heating up to + 1200C under pressure)

d) disinfection (treatment with chemicals - antiseptics)

e) pasteurization - disinfection at 60-70 0 C for 20-30 minutes.

f) at home: pickling in acetic acid, salting, cooling and freezing products;

g) use of antibiotics

THE KINGDOM OF VIRUSES

Viruses (from Latin virus - poison) are particles that are a transitional form between living and non-living matter and do not have a cellular structure.

Opened in 1892 Russian scientist D. Ivanovsky. He discovered and described the tobacco mosaic virus. This virus infects tobacco, causing the destruction of chlorophyll, which causes some areas to become lighter.

Differences from inanimate matter:

1. the ability to reproduce similar forms (to reproduce)
2. possession of heredity and variability.

The structure of viruses:

an RNA or DNA molecule enclosed in a protein shell, which is called a capsid (Fig. 16).

Rice. 18 Bacteriophage

Features of life

1. Having penetrated the cell, the virus changes its metabolism, directing all its activities to the production of viral nucleic acid and viral proteins .
2. Inside the cell, self-assembly of viral particles from synthesized nucleic acid molecules and proteins occurs.
3. Sometimes in viral DNA integrates into DNA l labels- host, causing cellular DNA to produce viral DNA.
4. Until the moment of death, a huge number of viral particles has time to be synthesized in the cell. Ultimately, the cell dies, its shell bursts, and the viruses leave the host cell (Fig. 17).

Viral diseases:

Meaning of viruses:

Biological mutagens (cause mutations).

Bacteriophages are used in medicine against bacteria.

Used in genetic engineering.

pathogens.

HIV is the human immunodeficiency virus.

The disease AIDS was discovered in 1981, and in 1983. causative agent - HIV. HIV has a unique variability that is 5 times greater than that of the influenza virus and 100 times greater than that of the hepatitis B virus. The continuous genetic and antigenic variability of the virus in the human population leads to the emergence of new HIV virions, which greatly complicates the problem of obtaining a vaccine and makes it difficult to conduct special AIDS prevention.

AIDS has a very long incubation period. In adults, it averages 5 years. It is assumed that HIV can persist in the human body for life.

Ways of HIV transmission - infection:

1. Sexual (with sperm and vaginal secretion) - with a non-permanent sexual partner and homosexual relationships; with artificial insemination.

2. When using contaminated medical instruments, drug addicts - with one syringe.

3. From mother to child: in utero, during childbirth, while breastfeeding.

4. Through the blood: during blood transfusion, transplantation of organs and tissues.

The virus infects that part of the human immune system that is associated with T - lymphocytes blood providing cellular and humoral immunity. As a result of the disease, the human body becomes defenseless against infectious and neoplastic diseases, which the normal immune system can cope with.

Stages of AIDS disease.

I. Infection with the HIV virus: weekly fever, swollen lymph nodes, rash. A month later, antibodies to the HIV virus are detected in the blood.

II. hidden period(from several weeks to several years): ulceration of the mucosa, fungal skin lesions, weight loss, diarrhea, fever.

III. AIDS: pneumonia, tumors (Kaposi's sarcoma), sepsis and other infectious diseases.

The causative agent of AIDS kills:

50 - 70o alcohol → a few seconds.

Boiling → instantly.

To = 56°C → 30 minutes.

Disinfectants (chloramine, bleach) → instantly.

Entering the gastrointestinal tract → destroyed by digestive enzymes and hydrochloric acid.

Test tasks in the OGE format

Task 3. Kingdom of Bacteria. Kingdom of Viruses.

3.1 Bacteria do not have a formed nucleus, so they are classified as

1) eukaryotes 2) prokaryotes 3) autotrophs 4) heterotrophs

3.2. Bacterial cells differ from plant and animal cells by the absence of:

1) cell wall 2) cytoplasm 3) nucleus 4) ribosomes

3.3. What bacteria are considered the "orderlies of the planet"

1) decay 2) acetic acid 3) lactic acid 4) nodule

3.4. Most bacteria in the cycle play a role

1) producers of organic substances 2) consumers of organic substances

3) destroyers of organic substances 4) concentrators of organic substances

3.5. To lubek bacteria enter into symbiosis with leguminous plants, improving their nutrition

1) potassium 2) phosphorus 3) nitrogen 4) calcium

3.6. bacteria multiply

1) spores 2) using germ cells 3) vegetatively 4) by cell division

3.7. Most bacteria by way of feeding

1) producers of organic substances 2) symbiotic organisms

3) consumers of inorganic substances 4) destroyers of organic substances

3.8. Nodule bacteria that live in the roots of leguminous plants are

3.9. The genetic material of a bacterium is contained in

formed nucleus 3) several chromosomes

in a circular DNA molecule 4) in a circular RNA molecule

3.10. Bacteria that use oxygen for respiration are called

3.11. Bacteria that live in association with other organisms are

3.12. Photosynthetic blue-green cyanobacteria are

3.13. Spores in bacteria provide

1) transfer of adverse conditions 2) sexual reproduction

3) vegetative reproduction 4) asexual reproduction

3.14. What biological object is shown in the picture?

1) bacterial cell 2) fungal spore 3) HIV virus 4) plant seed

3.15. Which of the methods of combating pathogenic bacteria is most effective in the operating unit?

1) pasteurization 2) regular ventilation

3) exposure to ultraviolet rays 4) washing floors with hot water

3.16. To which group of bodies of living nature does the object shown in the figure belong:

1) eukaryotes 2) nanorobots 3) prokaryotes 4) viruses

Task 23. Choose three correct answers from six and write down the numbers under which they are indicated.

1. 23.1. Choose the conditions that allow saprophytic bacteria to thrive in nature

1) the complexity of the internal structure 4) the ability to photosynthesis

2) the complexity of metabolism 5) the simplicity of the internal structure

3) the ability to multiply rapidly 6) nutrition with organic substances

1. 23.2. Choose the right statements

1) nodule bacteria enrich the soil with nitrogen

2) bacteria make it difficult for plants to absorb minerals

4) decay bacteria feed on the remains of plants and animals

5) sauerkraut and silage of feed is caused by lactic acid bacteria

6) so that the products do not deteriorate, they need access to oxygen

Task 25. Establish a correspondence: for each element of the first column, select the corresponding element from the second column.

25.1. Match

Signs of the Kingdom of Organisms

1) eukaryotes

2) used for baking bread A) mushrooms

3) unicellular and multicellular B) bacteria

4) there is one chromosome in a cell

5) some are capable of chemosynthesis and photosynthesis

6) many are pathogens

25.2. Match

Features Cell type

1) there is no formed core A) procaritis

2) chromosomes are located in the nucleus B) eukaryotic

3) there is a Golgi apparatus

4) there is one ring chromosome in the cell

5) ATP is produced in mitochondria

Task 27. Choose from the proposed list and insert the missing words into the text, using their digital designations for this. Write the numbers of the selected words in the place of the gaps in the text.

27.1. VIRUSES

Viruses - ---------- (A) life forms that exhibit some of the characteristics of living organisms only inside other cells. The virus consists of genetic material and -------(B). Genetic material is formed by ------ (B): DNA or RNA. DNA-containing viruses, after entering the cell, insert their DNA into the cell's own genetic material. RNA-containing viruses, after entering the cell, first convert the information of their RNA into DNA, by -------(D), and then it is integrated into the genetic material of the cell.

List of terms:

2) nucleic acid

3) cell membrane

4) protein capsid

5) reverse transcription

6) broadcast

7) unicellular

8) non-cellular

Write in the table the selected numbers under the corresponding letters. Answer:

27.2. BACTERIA

Bacteria are basically _______(A) organisms. Under adverse conditions, they can form ______(B). Many bacteria have ______(B) with which they move. Hereditary information in these microorganisms is stored in the form ______(G).

List of terms:

2) nuclear substance

3) pseudopod

7) unicellular

8) multicellular

Write in the table the selected numbers under the corresponding letters.

27.3. BIOTECHNOLOGY

Biotechnology is a discipline that studies the possibilities of using biological objects to create living organisms with the necessary properties. The greatest success has been achieved in the field of changing the genetic apparatus of bacteria. Bacteria have learned to introduce new genes into the genome with the help of small ring-shaped DNA molecules - _______ (A) present in bacterial cells. The necessary _______ (B) is “pasted” into them, and then they are added to the bacterial culture, for example _______ (C). After that, the hybrid circular DNA _______ (G) in the cell, reproducing dozens of its copies, which provide the synthesis of new proteins. 3.7

AAABBB

ABBAB

Literature

Zayats R.G., Butilovsky V.E., Davydov V.V. Biology. The entire school curriculum in tables. Minsk: Open book, 2016.-448 p.

Zayats R.G., Rachkovskaya I.V., Butilovsky V.E., Davydov V.V. Biology for applicants: questions, answers, tests, tasks. - Minsk: Unipress, 2011.-768 p.

"I will solve the OGE": biology. Educational system of Dmitry Gushchin [Electronic resource] - URL: http:// oge.sdamgia.ru

Theory for preparation for block No. 4 of the Unified State Examination in biology: with system and diversity of the organic world.

bacteria

bacteria refers to prokaryotic organisms that do not have nuclear membranes, plastids, mitochondria and other membrane organelles. They are characterized by the presence of one circular DNA. The size of the bacteria is quite small 0.15-10 microns. Cells can be divided into three main groups according to their shape: spherical , or cocci , rod-shaped and tortuous . Bacteria, although they belong to prokaryotes, have a rather complex structure.

The structure of bacteria

The bacterial cell is covered with several outer layers. The cell wall is essential for all bacteria and is the main component of the bacterial cell. The cell wall of bacteria gives shape and rigidity and, in addition, performs a number of important functions:

• protects the cell from damage
• involved in metabolism
• many pathogenic bacteria are toxic
• involved in the transport of exotoxins

The main component of the cell wall of bacteria is a polysaccharide murein . Bacteria are divided into two groups based on the structure of the cell wall: gram-positive (stained by Gram when preparing preparations for microscopy) and gram-negative (not stained by this method) bacteria.

Forms of bacteria: 1 - micrococci; 2 - diplococci and tetracocci; 3 - sarcins; 4 - streptococci; 5 - staphylococci; 6, 7 - sticks, or bacilli; 8 - vibrios; 9 - spirilla; 10 - spirochetes

Structure of a bacterial cell: I - capsule; 2 - cell wall; 3 - cytoplasmic membrane;4 - nucleoid; 5 - cytoplasm; 6 - chromatophores; 7 - thylakoids; 8 - mesosome; 9 - ribosomes; 10 - flagella; II - basal body; 12 - drank; 13 - drops of fat

Cell walls of gram-positive (a) and gram-negative (b) bacteria: 1 - membrane; 2 - mucopeptides (murein); 3 - lipoproteins and proteins

Scheme of the structure of the bacterial cell wall: 1 - cytoplasmic membrane; 2 - cell wall; 3 - microcapsule; 4 - capsule; 5 - mucous layer

There are three obligatory cellular structures of bacteria:

1. nucleoid
2. ribosomes
3. cytoplasmic membrane (CPM)

The organs of movement of bacteria are flagella, which can be from 1 to 50 or more. Cocci are characterized by the absence of flagella. Bacteria have the ability to directed forms of movement - taxis.

taxis are positive if the movement is directed towards the source of the stimulus, and negative when the movement is directed away from it. The following types of taxis can be distinguished.

Chemotaxis- movement based on the difference in the concentration of chemicals in the environment.

Aerotaxis- on the difference in oxygen concentrations.

When reacting to light and magnetic field, respectively, phototaxis and magnetotaxis.

An important component in the structure of bacteria are derivatives of the plasma membrane - pili (villi). Pili take part in the fusion of bacteria into large complexes, the attachment of bacteria to the substrate, and the transport of substances.

Bacteria nutrition

By type of nutrition, bacteria are divided into two troupes: autotrophic and heterotrophic. Autotrophic bacteria synthesize organic substances from inorganic ones. Depending on what energy autotrophs use to synthesize organic substances, photo- (green and purple sulfur bacteria) and chemosynthetic bacteria (nitrifying, iron bacteria, colorless sulfur bacteria, etc.) are distinguished. Heterotrophic bacteria feed on ready-made organic matter of dead residues (saprotrophs) or living plants, animals and humans (symbionts).

Saprotrophs include decay and fermentation bacteria. The former break down nitrogen-containing compounds, the latter - carbon-containing ones. In both cases, the energy necessary for their life activity is released.

It should be noted the great importance of bacteria in the nitrogen cycle. Only bacteria and cyanobacteria are able to assimilate atmospheric nitrogen. Subsequently, the bacteria carry out ammonification reactions (decomposition of proteins from dead organics to amino acids, which are then deaminated to ammonia and other simple nitrogen-containing compounds), nitrification (ammonia is oxidized to nitrites, and nitrites to nitrates), denitrification (nitrates are reduced to gaseous nitrogen).

Breath bacteria

According to the type of respiration, bacteria can be divided into several groups:

• obligate aerobes: grow with free access of oxygen
• facultative anaerobes: develop both with the access of atmospheric oxygen, and in the absence of it
• obligate anaerobes: develop in the complete absence of oxygen in the environment

Reproduction of bacteria

Bacteria reproduce by simple binary cell division. This is preceded by self-doubling (replication) of DNA. Budding occurs as an exception.

Some bacteria have simplified forms of the sexual process. For example, in Escherichia coli, the sexual process resembles conjugation, in which part of the genetic material is transferred from one cell to another upon direct contact. After that, the cells are separated. The number of individuals as a result of the sexual process remains the same, but there is an exchange of hereditary material, i.e., genetic recombination takes place.

Spore formation is characteristic of only a small group of bacteria in which two types of spores are known: endogenous, formed inside the cell, and microcysts, formed from the whole cell. With the formation of spores (microcysts) in a bacterial cell, the amount of free water decreases, enzymatic activity decreases, the protoplast shrinks and becomes covered with a very dense shell. Spores provide the ability to endure adverse conditions. They withstand prolonged drying, heating above 100°C and cooling to almost absolute zero. In the normal state, the bacteria are unstable when dried, exposed to direct sunlight, temperature rises to 65-80 ° C, etc. Under favorable conditions, spores swell and germinate, forming a new vegetative cell of bacteria.

Despite the constant death of bacteria (eating them by protozoa, the action of high and low temperatures, and other adverse factors), these primitive organisms have survived from ancient times due to the ability to rapidly reproduce (a cell can divide every 20-30 minutes), the formation of spores, extremely resistant to environmental factors, and their ubiquitous distribution.

Vaccination

Remembering the heated debates on the issues of evolution and vitalism, we must not forget that people's interest in theoretical biology arose as a result of intensive studies in medicine, persistent study of functional disorders in the body. No matter how fast biological science developed in theoretical terms, no matter how far it moved away from the daily needs of practice, anyway, sooner or later it had to return to the needs of medicine.
The study of theory is by no means something abstract and unjustified, since the introduction of the achievements of theoretical science allows practice to move forward rapidly. And although applied science can develop purely empirically, without theory this development is much slower and more uncertain.
As an example, consider the history of the study of infectious diseases. Until the beginning of the 19th century. doctors, in fact, were completely helpless during the epidemics of plague or other infectious diseases that flared up on our planet from time to time. Smallpox is one of the diseases from which mankind suffered. It was tragic that it spread like a real natural disaster, every third of the sick died, and the survivors remained disfigured for life: faces covered with mountain ash repelled even loved ones.
However, it has been observed that the past illness provided immunity in the next outbreak. Therefore, many considered it more expedient not to avoid the disease, but to endure it, but in a very weak form that would not be life-threatening and would not disfigure the patient. In this case, the person would be guaranteed against repeated diseases. In countries such as Turkey and China, they have long tried to infect people with the contents of pustules from patients with a mild form of smallpox. The risk was great, because sometimes the disease proceeded in a very severe form. At the beginning of the XVIII century. similar vaccinations were carried out in England, but it is difficult to say whether they brought more benefit or harm. Being engaged in practical medical activities, the Englishman Edward Jenner (1749–1823) studied the protective properties of cowpox known in folk medicine: people who have had it become immune to both cowpox and human smallpox. After long and careful observation, on May 14, 1796, Jenner performed the first cowpox inoculation on an eight-year-old boy, using material taken from a woman with cowpox. The vaccination was accompanied by malaise. And two months later, the boy was infected with pus from the pustule of a smallpox patient - and remained healthy. In 1798, after repeating this experience many times, Jenner published the results of his work. He suggested calling the new method vaccination (from the Latin vaccinia - cowpox).
The fear of smallpox was so great that Jenner's method was accepted with enthusiasm, and the resistance of the most conservative was quickly broken. Vaccination spread throughout Europe and the disease receded. In countries with highly developed medicine, doctors no longer felt helpless in the fight against smallpox. In the history of mankind, this was the first case of a quick and radical victory over a dangerous disease.
But only the development of the theory could bring further success. At that time, no one knew the causative agents of infectious diseases; it was not necessary to count on the use of mild forms for vaccination purposes. The task of biologists was to learn how to "make" their own "variants" of milder forms of the disease, but this required knowing much more than was known in Jenner's day.

germ theory of disease

Bacteriology

It is impossible to hope that someday it will be possible to completely isolate people from pathogenic microbes. Sooner or later, a person is at risk of infection. How to treat the patient? Of course, the body has its own means of fighting microbes: after all, as you know, sometimes a patient recovers even without assistance. The outstanding Russian biologist Ilya Ilyich Mechnikov (1845–1916) succeeded in illustrating such an “antibacterial struggle” of the organism. He showed that leukocytes perform the function of protection against pathogenic agents that have entered the body of animals and humans: they leave the blood vessels and rush to the site of infection, where a real battle of white blood cells with bacteria unfolds. Cells that perform a protective role in the body, Mechnikov called phagocytes.
In addition, recovery from many diseases is accompanied by the development of immunity (immunity), although no visible changes are found. This could be quite logically explained by the fact that antibodies are formed in the body of the ill person that have the ability to kill or neutralize the invading microbes. This view also explains the effect of vaccination; in the body of the vaccinated, antibodies are formed that are active against both the cowpox microbe and the smallpox microbe, which is very similar to it. Now victory is assured, but not over the disease itself, but over the microbe that causes it.
Pasteur outlined ways to fight anthrax, a deadly disease that was destroying herds of domestic animals. He found the causative agent of the disease and proved that it belongs to a special type of bacteria. Pasteur heated a preparation of bacteria to destroy their ability to cause disease (pathogenicity). The introduction of weakened (attenuated) bacteria into the body of an animal led to the formation of antibodies capable of resisting the original pathogenic bacteria.
In 1881, Pasteur staged an extremely revealing experiment. For the experiment, a herd of sheep was taken, one part of which was injected with weakened anthrax bacteria, and the other remained unvaccinated. After some time, all the sheep were infected with pathogenic strains. The vaccinated sheep showed no signs of the disease; unvaccinated sheep contracted anthrax and died.
Similar methods were used by Pasteur to fight chicken cholera and, most significantly, with one of the most terrible diseases - rabies (or rabies), transmitted to humans from infected wild or domestic animals.
The success of Pasteur's germ theory revived interest in bacteria. The German botanist Ferdinand Julius Kohn (1828–1898) studied plant cells under a microscope. He showed, for example, that the protoplasms of plant and animal cells are essentially identical. In the 60s of the XIX century, he turned to the study of bacteria. Cohn's greatest merit was the establishment of the vegetable nature of bacteria. He was the first to clearly separate bacteria from protozoa and tried to systematize bacteria according to genera and species. This allows us to consider Kohn the founder of modern bacteriology.
Cohn was the first to notice the talent of the young German physician Robert Koch (1843–1910). In 1876, Koch isolated the bacterium that causes anthrax and learned how to grow it. The support of Cohn, who became acquainted with the work of Koch, played an important role in the life of the great microbiologist. Koch cultivated bacteria on a solid medium - gelatin (which was later replaced by agar, extracted from seaweed), and not in a liquid poured into test tubes. This technical improvement has brought many advantages. In a liquid environment, bacteria of different types mix easily, and it is difficult to determine which one causes a particular disease. If the culture is applied as a smear on a solid medium, individual bacteria, dividing many times, form colonies of new cells, strictly fixed in their position. Even if the initial culture consists of a mixture of different types of bacteria, each colony is a pure cell culture, which allows you to accurately determine the type of pathogenic microbes. Koch first poured the medium onto a flat piece of glass, but his assistant Julius Richard Petri (1852–1921) replaced the glass with two flat, shallow glass cups, one of which served as a lid. Petri dishes are still widely used in bacteriology. Using the developed method for isolating pure microbial cultures, Koch and his collaborators isolated the causative agents of many diseases, including tuberculosis (1882).

Insects

Nutrition Factors

During the last third of the last century, the germ theory dominated the minds of most doctors, but there were those who held a different opinion. The German pathologist Virchow - the most famous opponent of Pasteur's theory - believed that diseases were caused by a disorder in the body itself rather than external agents. Virchow's merit was that over several decades of work in the Berlin municipality and national legislatures, he achieved such serious improvements in the field of hygiene as the purification of drinking water and the creation of an effective system for the disinfection of wastewater. Another scientist, Pettenkofer, did a lot in this area. He and Virchow can be considered the founders of modern social hygiene (the study of disease prevention in human society).
Such measures to prevent the spread of epidemics, of course, were no less important than the direct impact on the microbes themselves.
Naturally, the concern for cleanliness, which Hippocrates preached, retained its significance even when the role of microbes became clear to everyone. The advice of Hippocrates regarding the need for a full and varied diet remained in force, and their importance was revealed not only for maintaining health in general, but also as a specific method of preventing certain diseases. The idea that malnutrition could be the cause of disease was considered "old-fashioned" - scientists were obsessed with microbes - but it was supported by fairly strong evidence.
During the Age of Discovery, people spent long months on board ships, eating only those foods that could be well preserved, since the use of artificial cold was not yet known. The terrible scourge of sailors was scurvy. The Scottish physician James Lind (1716-1794) drew attention to the fact that diseases are found not only on board ships, but also in besieged cities and prisons - everywhere where food is monotonous. Perhaps the disease is caused by the absence of any product in the diet? Lind tried to diversify the diet of sailors suffering from scurvy, and soon discovered the healing effect of citrus fruits. The great English navigator James Cook (1728–1779) introduced citrus fruits into the diet of the crew of his Pacific expeditions in the 70s of the 18th century. As a result, only one person died of scurvy. In 1795, during the war with France, the sailors of the British Navy began to be given lemon juice, and not a single case of scurvy was noted.
However, such purely empirical achievements, in the absence of the necessary theoretical justifications, were introduced very slowly. In the 19th century major discoveries in the field of nutrition related to the role of protein. It was found that some proteins, "complete", present in the diet, can support life, others, "inferior", like gelatin, are not able to do this. The explanation came only when the nature of the protein molecule was better known. In 1820, having treated a complex molecule of gelatin with acid, a simple molecule was isolated from it, which was called glycine. Glycine belongs to the class of amino acids. Initially, it was assumed that it serves as a building block for proteins, just as a simple sugar, glucose, is a brick from which starch is built. However, by the end of the XIX century. this theory was found to be untenable. Other simple molecules were obtained from a wide variety of proteins - all of them, differing only in details, belonged to the class of amino acids. The protein molecule turned out to be built not from one, but from a number of amino acids. By 1900, dozens of different amino acid building blocks were known. Now it no longer seemed incredible that proteins differ in the ratio of amino acids they contain. The first scientist to show that a particular protein may not have one or more amino acids that play an essential role in the life of an organism was the English biochemist Frederick Gowland Hopkins (1861–1947). In 1903, he discovered a new amino acid - tryptophan - and developed methods for its detection. Zein, a protein isolated from corn, was negative and therefore did not contain tryptophan. It turned out to be an inferior protein, since, being the only protein in the diet, it did not provide the vital activity of the organism. But even a small addition of tryptophan made it possible to prolong the life of experimental animals.
Subsequent experiments, carried out in the first decade of the 20th century, clearly showed that certain amino acids are synthesized in the mammalian organism from substances normally found in tissues. However, some of the amino acids must be supplied with food. The absence of one or more of these "essential" amino acids makes the protein defective, leading to illness and sometimes death. Thus, the concept of additional nutritional factors was introduced - compounds that cannot be synthesized in the body of animals and humans and must be included in food to ensure normal life.
Strictly speaking, amino acids are not a serious medical problem for nutritionists. Lack of amino acids usually occurs only with artificial and monotonous nutrition. Natural food, even if it is not very rich, provides the body with a sufficient variety of amino acids.
Since a disease such as scurvy is cured by lemon juice, it is reasonable to assume that lemon juice supplies the body with some missing nutritional factor. It is unlikely that it is an amino acid. Indeed, all known biologists of the XIX century. the ingredients of lemon juice, taken together or separately, could not cure scurvy. This food factor had to be a substance needed only in very small quantities and chemically different from the usual components of food.
Finding the mysterious substance was not so difficult. After the development of the doctrine of essential amino acids for life, more subtle nutritional factors were identified that the body needs only in trace amounts, but this did not happen in the process of studying scurvy.

vitamins

In 1886, the Dutch physician Christian Eijkman (1858–1930) was sent to Java to fight beriberi. There were reasons to think that this disease arises as a result of malnutrition. Japanese sailors suffered greatly from beriberi and stopped getting sick only when, in the 80s of the 19th century, milk and meat were introduced into their diet, which consisted almost exclusively of rice and fish. Aikman, however, being captivated by Pasteur's germ theory, was convinced that beriberi was a bacterial disease. He brought chickens with him, hoping to infect them with germs. But all his attempts were unsuccessful. True, in 1896, chickens suddenly fell ill with a disease similar to beriberi. Finding out the circumstances of the disease, the scientist found that just before the outbreak of the disease, chickens were fed polished rice from the hospital food warehouse. When they were transferred to the old food, recovery began. Gradually, Aikman became convinced that this disease could be caused and cured by a simple change in diet.
At first, the scientist did not appreciate the true significance of the data obtained. He suggested that the grains of rice contain some kind of toxin, which is neutralized by something contained in the shell of the grain, and since the shell is removed when the rice is peeled, unneutralized toxins remain in the polished rice. But why create a hypothesis about the presence of two unknown substances, a toxin and an antitoxin, when it is much easier to assume that there is some kind of nutritional factor needed in negligible amounts? This opinion was shared by Hopkins and the American biochemist Casimir Funk (born in 1884). They suggested that not only beriberi, but also such diseases as scurvy, pellagra and rickets, are explained by the absence of the smallest amounts of certain substances in food.
Still under the impression that these substances belong to the class of amines, Funk proposed in 1912 to call them vitamins (the amines of life). The name has taken root and has been preserved to this day, although it has since become clear that they have nothing to do with amines.
Vitamin hypothesis Hopkins - Funk was fully formulated, and the first third of the XX century. showed that various diseases can be cured by the appointment of a reasonable diet and diet. For example, the American physician Joseph Goldberger (1874–1929) discovered (1915) that the pellagra disease common in the southern states of the United States was by no means of microbial origin. In fact, it was caused by the absence of some vitamin and disappeared as soon as milk was added to the diet of patients. Initially, vitamins were known only that they were able to prevent and treat certain diseases. In 1913, the American biochemist Elmer Vernon McCollum (born in 1879) suggested that vitamins be called letters of the alphabet; this is how vitamins A, B, C and D appeared, and then vitamins E and K were added to them. It turned out that food containing vitamin B actually contains more than one factor that can affect more than one symptom complex. Biologists started talking about vitamins B1, B2, etc.
It turned out that it was the lack of vitamin B1 that caused beriberi, and the lack of vitamin B2 caused pellagra. Lack of vitamin C led to scurvy (the presence of small amounts of vitamin C in citrus juice explains their healing effect, which allowed Lind to cure scurvy), lack of vitamin D to rickets. Lack of vitamin A affected vision and caused night blindness. Vitamin B12 deficiency caused malignant anemia. These are the main diseases caused by vitamin deficiency. With the accumulation of knowledge about vitamins, all these diseases ceased to be a serious medical problem. Since the 30s of the 20th century, vitamins in their pure form began to be isolated and synthesized.