BACTERIA
a large group of unicellular microorganisms characterized by the absence of a cell nucleus surrounded by a membrane. At the same time, the genetic material of the bacterium (deoxyribonucleic acid, or DNA) occupies a very specific place in the cell - a zone called the nucleoid. Organisms with such a cell structure are called prokaryotes (“prenuclear”), in contrast to all others - eukaryotes (“true nuclear”), whose DNA is located in the nucleus surrounded by a shell. Bacteria, previously considered microscopic plants, are now classified into the independent kingdom Monera - one of five in the current classification system, along with plants, animals, fungi and protists.

Fossil evidence. Bacteria are probably the oldest known group of organisms. Layered stone structures - stromatolites - dated in some cases to the beginning of the Archeozoic (Archean), i.e. arose 3.5 billion years ago, - the result of the vital activity of bacteria, usually photosynthesizing, the so-called. blue-green algae. Similar structures (bacterial films impregnated with carbonates) are still formed today, mainly off the coast of Australia, the Bahamas, in the California and Persian Gulfs, but they are relatively rare and do not reach large sizes, because herbivorous organisms, such as gastropods, feed on them. Nowadays, stromatolites grow mainly where these animals are absent due to high salinity of water or for other reasons, but before the emergence of herbivorous forms during the evolution, they could reach enormous sizes, constituting an essential element of oceanic shallow water, comparable to modern coral reefs. In some ancient rocks, tiny charred spheres have been found, which are also believed to be the remains of bacteria. The first nuclear ones, i.e. eukaryotic, cells evolved from bacteria approximately 1.4 billion years ago.
Ecology. Bacteria are abundant in the soil, at the bottom of lakes and oceans - wherever organic matter accumulates. They live in the cold, when the thermometer is just above zero, and in hot acidic springs with temperatures above 90 ° C. Some bacteria tolerate very high salinity; in particular, they are the only organisms found in the Dead Sea. In the atmosphere, they are present in water droplets, and their abundance there usually correlates with the dustiness of the air. Thus, in cities, rainwater contains much more bacteria than in rural areas. There are few of them in the cold air of high mountains and polar regions, however, they are found even in the lower layer of the stratosphere at an altitude of 8 km. The digestive tract of animals is densely populated with bacteria (usually harmless). Experiments have shown that they are not necessary for the life of most species, although they can synthesize some vitamins. However, in ruminants (cows, antelopes, sheep) and many termites, they are involved in the digestion of plant food. Additionally, the immune system of an animal raised under sterile conditions does not develop normally due to lack of bacterial stimulation. The normal bacterial flora of the intestines is also important for suppressing harmful microorganisms that enter there.

STRUCTURE AND LIFE ACTIVITY OF BACTERIA

Bacteria are much smaller than the cells of multicellular plants and animals. Their thickness is usually 0.5-2.0 microns, and their length is 1.0-8.0 microns. Some forms are barely visible at the resolution of standard light microscopes (approximately 0.3 microns), but species are also known with a length of more than 10 microns and a width that also goes beyond the specified limits, and a number of very thin bacteria can exceed 50 microns in length. On the surface corresponding to the point marked with a pencil, a quarter of a million medium-sized representatives of this kingdom will fit.
Structure. Based on their morphological features, the following groups of bacteria are distinguished: cocci (more or less spherical), bacilli (rods or cylinders with rounded ends), spirilla (rigid spirals) and spirochetes (thin and flexible hair-like forms). Some authors tend to combine the last two groups into one - spirilla. Prokaryotes differ from eukaryotes mainly in the absence of a formed nucleus and the typical presence of only one chromosome - a very long circular DNA molecule attached at one point to the cell membrane. Prokaryotes also do not have membrane-enclosed intracellular organelles called mitochondria and chloroplasts. In eukaryotes, mitochondria produce energy during respiration, and photosynthesis occurs in chloroplasts (see also CELL). In prokaryotes, the entire cell (and primarily the cell membrane) takes on the function of a mitochondrion, and in photosynthetic forms, it also takes on the function of a chloroplast. Like eukaryotes, inside bacteria there are small nucleoprotein structures - ribosomes, necessary for protein synthesis, but they are not associated with any membranes. With very few exceptions, bacteria are unable to synthesize sterols, important components of eukaryotic cell membranes. Outside the cell membrane, most bacteria are covered with a cell wall, somewhat reminiscent of the cellulose wall of plant cells, but consisting of other polymers (they include not only carbohydrates, but also amino acids and bacteria-specific substances). This membrane prevents the bacterial cell from bursting when water enters it through osmosis. On top of the cell wall is often a protective mucous capsule. Many bacteria are equipped with flagella, with which they actively swim. Bacterial flagella are structured simpler and somewhat differently than similar structures of eukaryotes.

"TYPICAL" BACTERIAL CELL and its basic structures.

Sensory functions and behavior. Many bacteria have chemical receptors that detect changes in the acidity of the environment and the concentration of various substances, such as sugars, amino acids, oxygen and carbon dioxide. Each substance has its own type of “taste” receptors, and the loss of one of them as a result of mutation leads to partial “taste blindness.” Many motile bacteria also respond to temperature fluctuations, and photosynthetic species respond to changes in light intensity. Some bacteria perceive the direction of magnetic field lines, including the Earth's magnetic field, with the help of particles of magnetite (magnetic iron ore - Fe3O4) present in their cells. In water, bacteria use this ability to swim along lines of force in search of a favorable environment. Conditioned reflexes in bacteria are unknown, but they do have a certain kind of primitive memory. While swimming, they compare the perceived intensity of the stimulus with its previous value, i.e. determine whether it has become larger or smaller, and, based on this, maintain the direction of movement or change it.
Reproduction and genetics. Bacteria reproduce asexually: the DNA in their cell is replicated (doubled), the cell divides in two, and each daughter cell receives one copy of the parent DNA. Bacterial DNA can also be transferred between non-dividing cells. At the same time, their fusion (as in eukaryotes) does not occur, the number of individuals does not increase, and usually only a small part of the genome (the complete set of genes) is transferred to another cell, in contrast to the “real” sexual process, in which the descendant receives a complete set of genes from each parent. This DNA transfer can occur in three ways. During transformation, the bacterium absorbs “naked” DNA from the environment, which got there during the destruction of other bacteria or was deliberately “slipped” by the experimenter. The process is called transformation because in the early stages of its study the main attention was paid to the transformation (transformation) of harmless organisms into virulent ones in this way. DNA fragments can also be transferred from bacteria to bacteria by special viruses - bacteriophages. This is called transduction. A process reminiscent of fertilization and called conjugation is also known: bacteria are connected to each other by temporary tubular projections (copulatory fimbriae), through which DNA passes from a “male” cell to a “female” one. Sometimes bacteria contain very small additional chromosomes - plasmids, which can also be transferred from individual to individual. If the plasmids contain genes that cause resistance to antibiotics, they speak of infectious resistance. It is important from a medical point of view because it can spread between different species and even genera of bacteria, as a result of which the entire bacterial flora of, say, the intestines becomes resistant to the action of certain drugs.

METABOLISM

Partly due to the small size of bacteria, their metabolic rate is much higher than that of eukaryotes. Under the most favorable conditions, some bacteria can double their total mass and number approximately every 20 minutes. This is explained by the fact that a number of their most important enzyme systems function at a very high speed. Thus, a rabbit needs a matter of minutes to synthesize a protein molecule, while bacteria take seconds. However, in a natural environment, for example in soil, most bacteria are “on a starvation diet”, so if their cells divide, it is not every 20 minutes, but once every few days.
Nutrition. Bacteria are autotrophs and heterotrophs. Autotrophs (“self-feeding”) do not need substances produced by other organisms. They use carbon dioxide (CO2) as the main or only source of carbon. By incorporating CO2 and other inorganic substances, particularly ammonia (NH3), nitrates (NO-3) and various sulfur compounds, in complex chemical reactions, they synthesize all the biochemical products they need. Heterotrophs (“feeding on others”) use organic (carbon-containing) substances synthesized by other organisms, in particular sugars, as the main source of carbon (some species also need CO2). When oxidized, these compounds supply energy and molecules necessary for cell growth and functioning. In this sense, heterotrophic bacteria, which include the vast majority of prokaryotes, are similar to humans.
Main sources of energy. If mainly light energy (photons) is used for the formation (synthesis) of cellular components, then the process is called photosynthesis, and species capable of it are called phototrophs. Phototrophic bacteria are divided into photoheterotrophs and photoautotrophs depending on which compounds - organic or inorganic - serve as their main source of carbon. Photoautotrophic cyanobacteria (blue-green algae), like green plants, break down water molecules (H2O) using light energy. This releases free oxygen (1/2O2) and produces hydrogen (2H+), which can be said to convert carbon dioxide (CO2) into carbohydrates. Green and purple sulfur bacteria use light energy to break down other inorganic molecules, such as hydrogen sulfide (H2S), rather than water. The result also produces hydrogen, which reduces carbon dioxide, but no oxygen is released. This type of photosynthesis is called anoxygenic. Photoheterotrophic bacteria, such as purple nonsulfur bacteria, use light energy to produce hydrogen from organic substances, in particular isopropanol, but their source can also be H2 gas. If the main source of energy in the cell is the oxidation of chemicals, the bacteria are called chemoheterotrophs or chemoautotrophs, depending on whether the molecules serve as the main source of carbon - organic or inorganic. For the former, organic matter provides both energy and carbon. Chemoautotrophs obtain energy from the oxidation of inorganic substances, such as hydrogen (to water: 2H4 + O2 in 2H2O), iron (Fe2+ in Fe3+) or sulfur (2S + 3O2 + 2H2O in 2SO42- + 4H+), and carbon from CO2. These organisms are also called chemolithotrophs, thereby emphasizing that they “feed” on rocks.
Breath. Cellular respiration is the process of releasing chemical energy stored in “food” molecules for its further use in vital reactions. Respiration can be aerobic and anaerobic. In the first case, it requires oxygen. It is needed for the work of the so-called. electron transport system: electrons move from one molecule to another (energy is released) and ultimately join oxygen along with hydrogen ions - water is formed. Anaerobic organisms do not need oxygen, and for some species of this group it is even poisonous. The electrons released during respiration attach to other inorganic acceptors, such as nitrate, sulfate or carbonate, or (in one form of such respiration - fermentation) to a specific organic molecule, in particular glucose. See also METABOLISM.

CLASSIFICATION

In most organisms, a species is considered to be a reproductively isolated group of individuals. In a broad sense, this means that representatives of a given species can produce fertile offspring by mating only with their own kind, but not with individuals of other species. Thus, the genes of a particular species, as a rule, do not extend beyond its boundaries. However, in bacteria, gene exchange can occur between individuals not only of different species, but also of different genera, so whether it is legitimate to apply the usual concepts of evolutionary origin and kinship here is not entirely clear. Due to this and other difficulties, there is no generally accepted classification of bacteria yet. Below is one of the widely used variants.
KINGDOM OF MONERA

Phylum Gracilicutes (thin-walled gram-negative bacteria)

Class Scotobacteria (non-photosynthetic forms, such as myxobacteria) Class Anoxyphotobacteria (non-oxygen-producing photosynthetic forms, such as purple sulfur bacteria) Class Oxyphotobacteria (oxygen-producing photosynthetic forms, such as cyanobacteria)

Phylum Firmicutes (thick-walled gram-positive bacteria)

Class Firmibacteria (hard-celled forms, such as clostridia)
Class Thallobacteria (branched forms, e.g. actinomycetes)

Phylum Tenericutes (Gram-negative bacteria without a cell wall)

Class Mollicutes (soft-celled forms, such as mycoplasmas)

Phylum Mendosicutes (bacteria with defective cell walls)

Class Archaebacteria (ancient forms, e.g. methane-forming)

Domains. Recent biochemical studies have shown that all prokaryotes are clearly divided into two categories: a small group of archaebacteria (Archaebacteria - "ancient bacteria") and all the rest, called eubacteria (Eubacteria - "true bacteria"). It is believed that archaebacteria, compared to eubacteria, are more primitive and closer to the common ancestor of prokaryotes and eukaryotes. They differ from other bacteria in several significant features, including the composition of ribosomal RNA (rRNA) molecules involved in protein synthesis, the chemical structure of lipids (fat-like substances) and the presence in the cell wall of some other substances instead of the protein-carbohydrate polymer murein. In the above classification system, archaebacteria are considered only one of the types of the same kingdom, which unites all eubacteria. However, according to some biologists, the differences between archaebacteria and eubacteria are so profound that it is more correct to consider archaebacteria within Monera as a special subkingdom. Recently, an even more radical proposal has appeared. Molecular analysis has revealed such significant differences in gene structure between these two groups of prokaryotes that some consider their presence within the same kingdom of organisms to be illogical. In this regard, it is proposed to create a taxonomic category (taxon) of an even higher rank, calling it a domain, and divide all living things into three domains - Eucarya (eukaryotes), Archaea (archaebacteria) and Bacteria (current eubacteria).

ECOLOGY

The two most important ecological functions of bacteria are nitrogen fixation and mineralization of organic residues.
Nitrogen fixation. The binding of molecular nitrogen (N2) to form ammonia (NH3) is called nitrogen fixation, and the oxidation of the latter to nitrite (NO-2) and nitrate (NO-3) is called nitrification. These are vital processes for the biosphere, since plants need nitrogen, but they can only absorb its bound forms. Currently, approximately 90% (approx. 90 million tons) of the annual amount of such “fixed” nitrogen is provided by bacteria. The rest is produced by chemical plants or occurs during lightning strikes. Nitrogen in the air, which is approx. 80% of the atmosphere is bound mainly by the gram-negative genus Rhizobium and cyanobacteria. Rhizobium species enter into symbiosis with approximately 14,000 species of leguminous plants (family Leguminosae), which include, for example, clover, alfalfa, soybeans and peas. These bacteria live in the so-called. nodules - swellings formed on the roots in their presence. Bacteria obtain organic substances (nutrition) from the plant, and in return supply the host with fixed nitrogen. Up to 225 kg of nitrogen per hectare is fixed in this way per year. Non-leguminous plants, such as alder, also enter into symbiosis with other nitrogen-fixing bacteria. Cyanobacteria photosynthesize, like green plants, releasing oxygen. Many of them are also capable of fixing atmospheric nitrogen, which is then consumed by plants and ultimately animals. These prokaryotes serve as an important source of fixed nitrogen in the soil in general and rice paddies in the East in particular, as well as its main supplier for ocean ecosystems.
Mineralization. This is the name given to the decomposition of organic residues into carbon dioxide (CO2), water (H2O) and mineral salts. From a chemical point of view, this process is equivalent to combustion, so it requires large amounts of oxygen. The top layer of soil contains from 100,000 to 1 billion bacteria per 1 g, i.e. approximately 2 tons per hectare. Typically, all organic residues, once in the ground, are quickly oxidized by bacteria and fungi. More resistant to decomposition is a brownish organic substance called humic acid, which is formed mainly from lignin contained in wood. It accumulates in the soil and improves its properties.

BACTERIA AND INDUSTRY

Given the variety of chemical reactions bacteria catalyze, it is not surprising that they have been widely used in manufacturing, in some cases since ancient times. Prokaryotes share the glory of such microscopic human assistants with fungi, primarily yeast, which provide most of the processes of alcoholic fermentation, for example, in the production of wine and beer. Now that it has become possible to introduce useful genes into bacteria, causing them to synthesize valuable substances such as insulin, the industrial application of these living laboratories has received a new powerful incentive. See also GENETIC ENGINEERING.
Food industry. Currently, bacteria are used by this industry mainly for the production of cheeses, other fermented milk products and vinegar. The main chemical reactions here are the formation of acids. Thus, when producing vinegar, bacteria of the genus Acetobacter oxidize the ethyl alcohol contained in cider or other liquids to acetic acid. Similar processes occur when cabbage is sauerkraut: anaerobic bacteria ferment the sugars contained in the leaves of this plant into lactic acid, as well as acetic acid and various alcohols.
Ore leaching. Bacteria are used for leaching of low-grade ores, i.e. converting them into a solution of salts of valuable metals, primarily copper (Cu) and uranium (U). An example is the processing of chalcopyrite, or copper pyrite (CuFeS2). Heaps of this ore are periodically watered with water, which contains chemolithotrophic bacteria of the genus Thiobacillus. During their life activity, they oxidize sulfur (S), forming soluble copper and iron sulfates: CuFeS2 + 4O2 in CuSO4 + FeSO4. Such technologies greatly simplify the extraction of valuable metals from ores; in principle, they are equivalent to the processes that occur in nature during the weathering of rocks.
Recycling. Bacteria also serve to convert waste materials, such as sewage, into less hazardous or even useful products. Wastewater is one of the most pressing problems of modern humanity. Their complete mineralization requires huge amounts of oxygen, and in ordinary reservoirs where it is customary to dump this waste, there is no longer enough oxygen to “neutralize” it. The solution lies in additional aeration of wastewater in special pools (aeration tanks): as a result, mineralizing bacteria have enough oxygen to completely decompose organic matter, and in the most favorable cases, drinking water becomes one of the final products of the process. The insoluble sediment remaining along the way can be subjected to anaerobic fermentation. To ensure that such water treatment plants take up as little space and money as possible, a good knowledge of bacteriology is necessary.
Other uses. Other important areas of industrial application of bacteria include, for example, flax lobe, i.e. separation of its spinning fibers from other parts of the plant, as well as the production of antibiotics, in particular streptomycin (bacteria of the genus Streptomyces).

COMBATING BACTERIA IN INDUSTRY

Bacteria are not only beneficial; The fight against their mass reproduction, for example in food products or in the water systems of pulp and paper mills, has become a whole area of ​​activity. Food spoils under the influence of bacteria, fungi and its own enzymes that cause autolysis ("self-digestion"), unless they are inactivated by heat or other means. Since bacteria are the main cause of spoilage, developing efficient food storage systems requires knowledge of the tolerance limits of these microorganisms. One of the most common technologies is pasteurization of milk, which kills bacteria that cause, for example, tuberculosis and brucellosis. The milk is kept at 61-63°C for 30 minutes or at 72-73°C for only 15 seconds. This does not impair the taste of the product, but inactivates pathogenic bacteria. Wine, beer and fruit juices can also be pasteurized. The benefits of storing food in the cold have long been known. Low temperatures do not kill bacteria, but they do prevent them from growing and reproducing. True, when frozen, for example, to -25° C, the number of bacteria decreases after a few months, but a large number of these microorganisms still survive. At temperatures just below zero, bacteria continue to multiply, but very slowly. Their viable cultures can be stored almost indefinitely after lyophilization (freeze-drying) in a protein-containing medium, such as blood serum. Other known methods of storing food include drying (drying and smoking), adding large amounts of salt or sugar, which is physiologically equivalent to dehydration, and pickling, i.e. placing in a concentrated acid solution. When the acidity of the environment corresponds to pH 4 and below, the vital activity of bacteria is usually greatly inhibited or stopped.

BACTERIA AND DISEASES

STUDYING BACTERIA

Many bacteria are easy to grow in so-called. culture medium, which may include meat broth, partially digested protein, salts, dextrose, whole blood, its serum and other components. The concentration of bacteria in such conditions usually reaches about a billion per cubic centimeter, causing the environment to become cloudy. To study bacteria, it is necessary to be able to obtain their pure cultures, or clones, which are the offspring of a single cell. This is necessary, for example, to determine what type of bacteria infected the patient and what antibiotic this type is sensitive to. Microbiological samples, such as throat or wound swabs, blood samples, water samples or other materials, are highly diluted and applied to the surface of a semi-solid medium: on it, round colonies develop from individual cells. The hardening agent for the culture medium is usually agar, a polysaccharide obtained from certain seaweeds and indigestible by almost any type of bacteria. Agar media is used in the form of “shoals”, i.e. inclined surfaces formed in test tubes standing at a large angle when the molten culture medium solidifies, or in the form of thin layers in glass Petri dishes - flat round vessels, closed with a lid of the same shape, but slightly larger in diameter. Usually, within a day, the bacterial cell manages to multiply so much that it forms a colony that is easily visible to the naked eye. It can be transferred to another environment for further study. All culture media must be sterile before starting to grow bacteria, and in the future measures should be taken to prevent the settlement of unwanted microorganisms on them. To examine bacteria grown in this way, heat a thin wire loop in a flame, touch it first to a colony or smear, and then to a drop of water applied to a glass slide. Having evenly distributed the taken material in this water, the glass is dried and quickly passed over the burner flame two or three times (the side with the bacteria should be facing up): as a result, the microorganisms, without being damaged, are firmly attached to the substrate. Dye is dripped onto the surface of the preparation, then the glass is washed in water and dried again. Now you can examine the sample under a microscope. Pure cultures of bacteria are identified mainly by their biochemical characteristics, i.e. determine whether they form gas or acids from certain sugars, whether they are able to digest protein (liquefy gelatin), whether they need oxygen for growth, etc. They also check whether they are stained with specific dyes. Sensitivity to certain medications, such as antibiotics, can be determined by placing small disks of filter paper soaked in these substances on a surface infested with bacteria. If any chemical compound kills bacteria, a bacteria-free zone is formed around the corresponding disk.

Collier's Encyclopedia. - Open Society. 2000 .

All bacteria have certain morphological properties (shape, size, the nature of their location in the smear) and tinctorial properties (ability to stain).

There are 4 main forms of bacteria (Fig. 1): spherical (spherical) or coccoid (from the Greek kokkos - grain); rod-shaped (cylindrical); crimped (spiral); threadlike. In addition, there are bacteria that have a triangular, star-shaped, plate-shaped shape. So-called square bacteria have been discovered, which form clusters of 8 or 16 cells in the form of a layer.

Rice. 1. Forms of unicellular bacteria: 1- micrococci; 2 – diplococci; 3 – streptococci; 4 – staphylococci; 5 – sarcins; 6 – rod-shaped bacteria; 7 – spirilla; 8 – vibrios (Schlegel G., 1987).

Coccoid bacteria usually have the shape of a regular ball, with a diameter of 1.0 - 1.5 microns; some are bean-shaped, lanceolate, ellipsoidal in shape. Based on the nature of the relative position of the cells formed after cell division, cocci are divided into the following groups:

Micrococci (from Latin micros - small). Cells divide in one plane and most often immediately separate from the mother. They are located singly, randomly. There are no saprophytes that are pathogenic for humans (Fig. 1.1).

Diplococci (from Latin diplos - double). Division occurs in one plane with the formation of pairs of cells that are either bean-shaped or lanceolate in shape. For example, the causative agent of gonorrhea is Neisseria gonorrhoeae, the causative agent of pneumonia is Streptococcus pneumoniae (Fig. 1.2).

Streptococci (from Latin streptos - chain). Cell division occurs in one plane, but the multiplying cells maintain connections with each other and form chains of varying lengths, reminiscent of strings of beads. Many streptococci are pathogenic for humans and cause various diseases: scarlet fever, sore throat, purulent inflammation and others. For example, Streptococcus pyogenes (Fig. 1.3).

Staphylococci (from Latin staphyle - bunch of grapes). Cells divide in several planes, and the resulting cells are arranged in clusters resembling bunches of grapes. Staphylococci cause more than 100 different human diseases. They are the most common causative agents of purulent inflammation. For example, Staphylococcus aureus (Fig. 1.4).

Tetracocci (from Latin tetra - four). Division occurs in two mutually perpendicular planes with the formation of tetrads. Species pathogenic to humans are very rare.

Sarcinas (from Latin sarcina – bundle, bale). Division occurs in three mutually perpendicular planes with the formation of packages (bales) of 8, 16, 32 or more individuals. They are especially common in the air. There are opportunistic representatives (Fig. 1.5).

Rod-shaped (cylindrical shapes) (Fig. 1.6).

Based on the location of the sticks, they are divided into:

Solitary or randomly located - monobacteria. For example, Escherihia coli.

Arranged in pairs (along one line) – diplobacillus, diplobacteria. For example, Pseudomonas.

Arranged in a chain - streptobacilli, streptobacteria. For example, Bacillus anthracis is the causative agent of anthrax.

By lenght:

Very short, less than 1.0 microns - coccobacteria. For example, Francisella tularensis is the causative agent of tularemia.

Short 1.5 - 3.0 microns. These include most pathogens of intestinal infections.

Long, more than 3.0 microns. For example, the causative agent of gas gangrene is Clostridium novyi.

The ends of the sticks can be:

Rounded. For example, Escherihia coli, etc.

Pointed. For example, Fusobacterium.

Thickened. For example, in the causative agent of diphtheria due to volutin grains (reserve nutrients).

Circumcised. For example, Bacillus anthracis is the causative agent of anthrax.

Based on the diameter of the sticks, they are divided into:

Thin (causative agent of tuberculosis - Mycobacterium tuberculosis).

Thick (causative agent of gas gangrene – Clostridium perfringens).

The rods that form the spore are divided into:

Bacilli are aerobic spore-forming bacteria. The spore of such rods is usually located centrally and its diameter does not exceed the width of the bacterium (Fig. 10).

Clostridia are anaerobic spore-forming bacteria. Their spores are located terminally or subterminally. It is large, which stretches the membrane of the bacteria, and they look like a spindle or a tennis racket (Fig. 10).

Twisted (spiral) shapes.

Based on the number and nature of the curls, as well as the diameter of the cells, they are divided into three groups:

Vibrios (from the Greek vibrio - I wriggle, bend) have one bend, not exceeding a quarter turn of the spiral. For example, Vibrio cholerae is the causative agent of cholera (Fig. 1.8).

Spirilla (from the Greek speira - curl) are cells with a large diameter and a small (2 - 3) number of curls. An example is Spirillium minor (Fig. 1.7).

Spirochetes (from the Greek speira - curl, chaita - hair) are spiral-shaped, motile bacteria. Among those pathogenic for humans are:

1. Treponema is a bacterium with 8-14 curls of equal amplitude. Treponema pallidum is the causative agent of syphilis.

   Borrelia are irregularly curved spirochetes, with 2–3 or more curls of uneven height. Borrelia recurretis – the causative agent of relapsing fever

   Leptospira - have a sigmoid or C-shape, about two dozen small curls, with hooks at the ends. Leptospira interrogans is the causative agent of leptospirosis.

Thread-like forms.

There are two types of filamentous bacteria: those that form temporary filaments and permanent ones.

Temporary threads, sometimes with branches, form rod-shaped bacteria when the conditions for their growth or regulation of cell division are violated (mycobacteria, corynebacteria, as well as rickettsia, mycoplasmas, many gram-negative and gram-positive bacteria). When the division regulation mechanism and normal growth conditions are restored, these bacteria restore their usual size.

Permanent filamentous forms are formed from rod-shaped cells connected into long chains either with the help of mucus, or sheaths, or bridges (sulfur bacteria, iron bacteria).

To study the tinctorial properties of microorganisms and their morphology, aniline dyes (basic, acidic and neutral) are used.

Basic paints are most widely used: methylene blue, basic magenta, gentian violet, vesuvin, chrysoidin, etc. Neutral (neutral red) and acidic (eosin) paints are less commonly used. Alcohol, water-alcohol and aqueous solutions are prepared from these paints. In some cases, to increase the coloring power of the solution, mordants are added to it, for example, carbolic acid, alkali, etc.

To determine the shape of bacteria and their relative position in a smear, use simple painting methods, i.e. Staining is carried out with one dye and the smear is painted with one color. For example, methylene blue is used to identify gonococci in a smear. This staining makes it possible to better identify the bean-shaped shape and paired arrangement of cocci.

To study the structure of a bacterial cell and identify the features of its structure, they use complex painting methods, which include a range of dyes, mordants and differentiating agents. Complex staining methods include: Gram, Neisser, Ozheshko, etc. methods.

Bacteria- the most ancient organisms currently living on our planet. The most ancient and most simply structured, but unknown to man for the longest time of all other organisms. The science that studies bacteria and some other microscopic organisms is called microbiology. Scientists suggest that bacteria appeared on Earth more than 3.5 billion years ago and for more than a billion years they were the only living organisms on the planet. Over their long history, these organisms have adapted to almost all possible conditions of existence. Bacteria are the smallest organisms. They are measured not in centimeters or even millimeters, but in micrometers.

Structure of Bacteria

Vital activity of bacteria

	Saprotrophs (substances of dead organisms)	Aerobic (breathe oxygen like plants and release carbon dioxide) Anaerobic (does not require oxygen)
Movement	With the help of flagella or due to wave-like contractions
Reproduction	Bacteria reproduce by division: the mother cell divides into two daughter cells. Within 20–30 minutes. young cells also begin to divide.
Meaning	Bacteria play an important role in the cycle of substances in nature. Soil bacteria decompose dead organisms, converting organic matter into mineral salts needed by plants. Pathogenic bacteria cause dangerous diseases in humans, animals, and plants. Rotting and fermentation bacteria can cause food spoilage, but man has learned to use fermentation bacteria to produce food and prepare feed. Fermentation bacteria that promote digestion also live in the human and animal bodies.

The importance of bacteria in nature

Bacterial cell shapes

(air, water, soil, buildings, products, living organisms)

	Bacterial cell shapes
	(spherical)		(sticks)		Vibrios

Bacteria are very small, incredibly ancient and to some extent quite simple microorganisms. According to the modern classification, they are classified into a separate domain of organisms, which indicates a significant difference between bacteria and other forms of life.

Bacteria are the most common and, accordingly, the most numerous living organisms; they are, without exaggeration, omnipresent and thrive in any environment: water, air, earth, as well as inside other organisms. So in one drop of water their number can reach several million, and in the human body there are about ten more of them than all our cells.

What are bacteria?

These are microscopic, predominantly unicellular organisms, the main difference of which is the absence of a cell nucleus. The basis of the cell, the cytoplasm contains ribosomes and a nucleoid, which serves as the genetic material of bacteria. All this is separated from the outside world by a cytoplasmic membrane or plasmalemma, which in turn is covered by a cell wall and a denser capsule. Some types of bacteria have external flagella; their number and size can vary greatly, but their purpose is always the same - they help bacteria move.

Structure and contents of a bacterial cell

What are bacteria?

Shapes and sizes

The shapes of different types of bacteria vary greatly: they can be round, rod-shaped, convoluted, stellate, tetrahedral, cubic, C- or O-shaped, or irregular.

Bacteria vary in size even more. Thus, Mycoplasma mycoides - the smallest species in the entire kingdom - has a length of 0.1 - 0.25 micrometers, and the largest bacterium Thiomargarita namibiensis reaches 0.75 mm - it can be seen even with the naked eye. On average, sizes range from 0.5 to 5 microns.

Metabolism or metabolism

When it comes to obtaining energy and nutrients, bacteria exhibit extreme diversity. But at the same time, it is quite easy to generalize them by dividing them into several groups.

According to the method of obtaining nutrients (carbons), bacteria are divided into:

• autotrophs- organisms that are capable of independently synthesizing all the organic substances they need for life;
• heterotrophs- organisms that are capable of transforming only ready-made organic compounds, and therefore require the help of other organisms to produce these substances for them.

By method of obtaining energy:

• phototrophs- organisms that produce the necessary energy as a result of photosynthesis
• chemotrophs- organisms that produce energy by carrying out various chemical reactions.

How do bacteria reproduce?

Growth and reproduction in bacteria are closely related. Having reached a certain size, they begin to reproduce. In most types of bacteria this process can occur extremely quickly. Cell division, for example, can occur in less than 10 minutes, and the number of new bacteria will grow exponentially as each new organism divides into two.

There are 3 different types of reproduction:

• division- one bacterium divides into two absolutely genetically identical ones.
• budding- one or more buds (up to 4) are formed at the poles of the mother bacterium, while the mother cell ages and dies.
• primitive sexual process- part of the DNA of the parent cells is transferred to the daughter, and a bacterium appears with a fundamentally new set of genes.

The first type is the most common and fastest, the latter is incredibly important, not only for bacteria, but for all life in general.

Bacteria(actually bacteria, actinomycetes, rickettsia and chlamydia, mycoplasmas and, possibly, viruses) - heterotrophs or autotrophs. During photosynthesis, oxygen is not released.

Bacteria are very small single-celled organisms. Bacteria were first observed under a microscope by Anthony van Leeuwenhoek in the 17th century.

Bacteria cell has a membrane (cell wall) like a plant cell. But the bacterium is elastic, non-cellulose. Under the shell there is a cell membrane, which ensures the selective flow of substances into the cell. It protrudes into the cytoplasm, increasing the surface of membrane formations on which many metabolic reactions take place. A significant difference between a bacterial cell and the cells of other organisms is absence formed core. Of the other organelles in bacterial cells, only ribosomes are present, on which protein synthesis occurs. Prokaryotes lack all other organelles.

Form bacteria are very diverse, they can be spherical - cocci, rod-shaped - bacilli, curved - vibrios, twisted - spirilla And spirochetes (Fig.).

Movement. Some bacteria have flagella with which they moving. Bacteria reproduce by simply dividing a cell into two. Under favorable conditions, a bacterial cell divides every 20 minutes.

Sporulation. If conditions are unfavorable, further proliferation of the bacterial colony is stopped or slowed down. Bacteria do not tolerate low and high temperatures well: when heated to 80 0 C, many die, and some, under unfavorable conditions, form disputes - resting stages covered with a dense shell. In this state they remain viable for quite a long time, sometimes several years. Spores of some bacteria can withstand freezing and temperatures up to 129 0 C. Sporulation is characteristic of bacilli, for example pathogens anthrax, tuberculosis.

Bacteria live everywhere - in soil, water, air, in plant organisms.

Method of nutrition. Many bacteria according to the way they feed are heterotrophic organisms, i.e. they use ready-made organic substances. Some of them, being saprophytes, destroys the remains of dead plants and animals, participates in the decomposition of manure, and promotes soil mineralization.

Bacterial processes alcohol, lactic acid fermentation used by humans (kefir). There are species that can live in the human body without causing harm. For example, in the human intestine lives coli.

Certain types of bacteria, settling on food products, cause their spoilage. Saprophytes include bacteria rotting and fermentation.

In addition to heterotrophs, there are also autotrophic bacteria, capable of oxidizing inorganic substances and using the released energy for the synthesis of organic substances. For example, soil azotobacteria enrich it with nitrogen, increasing fertility (nodule bacteria); they are located on the roots of leguminous plants - clover, lupine, peas. Autotrophs include sulfur bacteria And iron bacteria(they live in the depths of the ocean).

Prokaryotes include another group of microorganisms - cyanobacteria. (blue-green algae) these are autotrophs, have photosynthetic system and chlorophyll pigment. That's why they are green or blue-green in color. Cyanobacteria can be solitary, colonial, or filamentous (multicellular). They are similar in appearance to algae. Cyanobacteria are common in water, soil, hot springs, and are part of lichens.

Using the topic “Microorganisms” in environmental education of preschool children.

In which section of the program “Our Home is Nature” is the concept of microorganisms, including bacteria, given? How?

In the blocks “Soil - living earth” and “Forest”. “Waste-free production” in nature is shown, the role of bacteria as destroyers of plant residues (the fairy tale “How the Bear Lost the Stump”)

Mushrooms

Sub-kingdom Lower mushrooms. The vegetative phase consists of plasmodium - a multinucleate naked mobile protoplasmic mass devoid of cell walls (slime fungi, for example, mucor)

Sub-kingdom Higher mushrooms. There is no Plasmodium, the vegetative phase consists of threads (hyphae) or cells with a pronounced cell wall. (Real mushrooms).

Mushrooms is a group of living organisms that has characteristics similar to plants and animals. Mushrooms are currently classified as a separate kingdom of living beings. Why?

Like plants, mushrooms have:

tough cell membrane

unlimited growth,

they are motionless

reproduce by spores

feed by absorbing nutrients dissolved in water.

But they are not green, there are no flowers or seeds.

Like animals, mushrooms:

are not able to synthesize organic substances from inorganic ones,

do not have plastids and photosynthetic pigments,

accumulate glycogen rather than starch as a reserve nutrient,

the cell membrane contains chitin (like in insects), and not cellulose,

can synthesize uric acid.

But they do not move or swallow food.

Most often, traditionally, mushrooms are considered in botany courses, but in all new textbooks, mushrooms are no longer classified as plants.

Number of species. There are 100 thousand species known in the mushroom kingdom (according to some, the true number of mushroom species is at least 1.5 million). There are about 60 thousand species in our country.

Origin. Recently, the most justified assumption is that fungi originated from colorless primitive unicellular flagellated organisms, one of the first abodes of water bodies on our planet, and among them it was not yet possible to distinguish typical animals and plants. Appeared about 1 billion years ago. Mushrooms reached their heyday during the Carboniferous period - approximately 265 years ago. Probably, cap mushrooms arose simultaneously with higher plants and underwent joint evolution with them.

Mushroom structure. Let's look at the structure of a mushroom. Mushroom body - thallus- consists of thin threads - gifs . A collection of hyphae is called mycelium or mycelium (rice.) .

Only in the 19th century it was established that the mushroom consists of two parts. The first one is mycelium, which permeates the soil, rotting wood, even the trunks of living trees. It is often microscopic, and only when there is a lot of it, we distinguish it in the form of a whitish coating or in the form of strands or cords consisting of tiny intertwined threads. The smell of the mycelium is often much stronger than the smell of the mushrooms themselves.

The mycelium develops on the substrate (this is the base - for example, soil, tree trunk, etc.), while the hyphae penetrate into the substrate and grow, branching repeatedly. Mushrooms reproduce vegetatively - by parts of mycelium and spores.

The second part of the mushroom - what we usually call the mushroom - is its fruiting body. It is connected to the mycelium by the base of the stalk. During the development of fruiting bodies, fungal hyphae are tightly intertwined and form false tissue. Researchers have always been amazed by the sudden appearance of cap mushrooms. The mushroom grows 1-2 cm per day, the life of the fruiting body of the cap mushroom is only about 10 days.

The fruiting bodies consist of a stem and a cap. In some mushrooms, the lower layer of the cap is formed by radially arranged plates - this is lamellar mushrooms. These include russula, chanterelles, champignons, toadstool, fly agarics, etc. Other mushrooms have numerous tubes on the underside of the cap - these are tubular mushrooms. These include porcini mushroom, boletus, boletus, etc. Fungal spores ripen in tubes and on plates.

Dimensions. Most mushrooms are microscopic in size. At the same time, the largest living creature on Earth is considered to be a mushroom of the genus Armillaria (honey mushroom), discovered in the north of the state. Michigan, the mass of its mycelium is about 100 tons, area - 15 hectares, age 1500 years. Its hyphae interact with the root systems of the entire forest.

Classification and representatives. Mushrooms are divided into two subkingdoms: lower and higher mushrooms

Sub-kingdom lower: body - one multinucleate or uninucleate cell. Sexual reproduction is rare.

Representatives of lower fungi are moldy mushroom mỳkor (often found on bread) and late blight on nightshades. Molds develop in the soil, on wet foods, fruits, and vegetables. One part of the fungal hyphae penetrates into the substrate, and the other part rises above the surface. Spores mature at the ends of vertical hyphae.

Sub-kingdom higher: have multicellular hyphae.

Class Basidiomycetes, These include cap mushrooms (tubular and platinum and smut in an ear of cereal. They are characterized by multicellular mycelium, which develops in the soil and forms on the surface. fruiting bodies.

Cap mushrooms grow best where there is a sufficiently nutritious environment, optimal humidity and air temperature (i.e. in cool and moderately damp forests, the most favorable environment is in mixed forests), and for some species also the degree of illumination.

Predatory mushrooms: have adaptations for capturing small animals. For example, oyster mushroom secretes a substance that immobilizes nematodes, after which the hyphae penetrate their body.

Reproduction. Vegetative, sexual and asexual means.

Vegetative - areas of mycelium.

Asexual – one cell – budding (yeast), spores (penicillium).

Sexual . In primitive ones - the fusion of motile zoospores, in higher ones - the threads of the mycelium.

The fruiting body carries microscopic spores. Mushrooms produce a simply fantastic amount of spores - millions, billions and trillions (for example, the giant puffball). Most mushrooms have spores on the underside of the cap, on the surface of the tubes or plates, and come in different colors and shapes.

Meaning in nature

1. Fungi, along with bacteria, play an important role in the cycle of substances in nature. With the help of enzymes, they actively decompose the remains of animals and plants and organic substances that fall into the soil, mineralize them, and participate in the formation of a fertile layer of soil - humus.

Specialized ecological groups: keratinophiles, coprophiles, xylotrophs, carbophiles, herbophiles, carnivores, mycophiles, phytopathogens.

2. Most mushrooms grow in the forest, in close cooperation with the roots of green plants, especially trees. The mycelium entwines their roots and even often penetrates inside. The mushroom and the tree exchange nutrients, and this is beneficial for both of them (the phenomenon of mutually beneficial cooperation - symbiosis). And under the tree, fruiting bodies appear - the mushrooms themselves: boletus, boletus. Mushrooms are closely related to their tree species. Some (ceps, russula) grow with many species. The porcini mushroom forms mycorrhiza with trees of about 50 species. Champignons, honey mushrooms, and umbrellas grow without the participation of trees, but there are fewer of them.

Herbaceous plants also have the phenomenon of mycorrhiza (especially orchids), but in them symbiosis exists with microscopic fungi that do not form large fruiting bodies.

The fungus gives the plant nitrogenous substances and vitamins, and the plant gives the fungus carbohydrates. Sometimes the fungus supplies water and minerals and “works” as root hairs.

Many aspects of the activity of fungi are not yet known to us.

For man. Mushrooms, like plants and animals, are constant companions of man, obligatory participants in his life and activities. In addition to being used as food, medicines are obtained from mushrooms - antibiotics (penicillin), vitamins, plant growth substances (gibberellin), enzymes.

They are assistants in baking and winemaking. Yeast causes alcoholic fermentation: it breaks down sugar into ethyl alcohol and carbon dioxide.

Mushrooms played a big role in the spiritual life of people (hallucinogenic properties). The red fly agaric is considered a “divine mushroom” in the countries of South America, India, and the peoples of the Far North. An aqueous solution of another mushroom, the panther fly agaric (brownish cap), has insecticidal properties. The fly agaric is poured with hot water and sugar is poured into a saucer. The flies arrive and then die.

Caesar mushroom get sick from the genus of fly agarics - the first among edibles.

Food product: Have been used as food for a long time. 20-30% pure protein. The digestibility of mushroom protein is 8 times lower than that of milk protein. There is more protein in the caps. Fats, min. ingredients, microelements (iron, calcium, phosphorus, iodine, potassium).

In our country, about 300 species of edible mushrooms are known, in the middle zone - about 200 species. Most edible mushrooms are little known (for example, the umbrella mushroom). The best edible ones are white, boletus, boletus, boletus, milk mushrooms, saffron milk caps, and autumn honey fungus.

Collection . Twisting, if this is impossible (the leg is fragile), then cut it off.

Poisonous mushrooms relatively little. Some poisonous ones are difficult to distinguish from edible ones. Some believe that poisonous mushrooms do not produce worms, but substances that are poisonous to humans may be harmless to insects.

There are about 80 species of mushrooms, the consumption of which can cause unpleasant phenomena, of which approximately 20 species are poisonous. Such mushrooms are divided into

inedible(bile mushroom, pepper, some types of russula),

conditionally edible(morels, strings, volushnik, black milk mushrooms, pigs; they need to be boiled for 15-20 minutes);

poisonous(20-25 species, pale toadstool and stinking fly agaric, they are deadly poisonous, false chanterelle, satanic mushroom, row mushrooms, some champignons). Even one mushroom can cause death. White pale toadstool, fly agarics “disguise” as champignons, greenfinch, and russula.

Help in case of poisoning: you need to lie down, drink cold liquid, put heating pads on your legs and stomach, and urgently provide medical assistance. Often symptoms of poisoning occur after a day or two or 2 weeks, when help can no longer be provided.

Some mushrooms - white dung beetle, gray dung beetle, etc. should never be consumed with alcoholic beverages, because their toxins dissolve not in water, but in alcohol; You should also not eat overgrown and wormy mushrooms, canned fried mushrooms, mushrooms near highways, fields and gardens, industrial enterprises - emissions and pesticides).

Medicinal properties. Penicillin and citric acid are obtained from mushrooms; substances obtained from mushrooms are used to treat mental illness, cancer, stomach ulcers, and tuberculosis.

From chaga- medicine befungin. Black growth on birch trunks. Its infusion is used instead of tea. Used as an antitumor and for the treatment of gastritis.

Veselka ordinary - for ointment in the treatment of polyarthritis.

White– for the treatment of gastrointestinal tract. diseases, there are antibiotics, cancer prevention. Especially strong in the spruce form.

Larch oiler relieves headaches.

Ryzhik– inhibits the growth of tuberculosis bacillus.

Shiitake mushroom(Japan, artificially grown) – prevention of high blood pressure, atherosclerosis, antitumor, and antiviral.

Oyster mushroom– has antitumor and antiviral properties.

Mushrooms in the city. Sidewalk champignon breaks through concrete and asphalt (in Moscow in the city center), common champignon, white dung beetle (edible, but lives only a few hours, cannot even be stored in the refrigerator), sulfur-yellow tinder fungus (up to half a meter and weighing 6-8 kg, annual ). You can’t pick mushrooms in the city, but in the forest - only no closer than 500 m from the road.

“Mushroom patch” – raincoat. There is a false raincoat (inedible) - its flesh is not white, it is dark.

Interesting shaped mushrooms. Many mushrooms have a bizarre shape: Judas ear, horned hare ears, donkey ears (all ears are edible), star mushrooms, ram mushroom, true tinder fungus, or “hoof mushroom”, “flower mushrooms”.

Breeding.Champignon- a child of darkness, he is bred in dark rooms. Oyster mushroom began to be cultivated in the last 20-30 years, it grows on wood or a substrate of sunflower cake. In general, about 10 types of different mushrooms are bred. Artificially grown mushrooms are an environmentally friendly product.