A message about bacteria in the human body. Beneficial bacteria. Where do bacteria in urine come from?

The totality of bacteria inhabiting the human body has a common name - microbiota. In the normal, healthy human microflora there are several million bacteria. Each of them plays an important role for the normal functioning of the human body.

In the absence of any type of beneficial bacteria, a person begins to get sick, the functioning of the gastrointestinal tract and respiratory tract is disrupted. Beneficial bacteria for humans are concentrated on the skin, in the intestines, and on the mucous membranes of the body. The number of microorganisms is regulated by the immune system.

Normally, the human body contains both beneficial and pathogenic microflora. Bacteria can be beneficial or pathogenic.

There are many more beneficial bacteria. They make up 99% of the total number of microorganisms.

In this situation, the necessary balance is maintained.

Among the different types of bacteria that live on the human body are:

• bifidobacteria;
• lactobacilli;
• enterococci;
• coli.

Bifidobacteria

This type of microorganism is the most common and is involved in the production of lactic acid and acetate. It creates an acidic environment, thereby neutralizing most pathogenic microbes. Pathogenic flora ceases to develop and cause processes of rotting and fermentation.

Bifidobacteria play an important role in a child’s life, since they are responsible for the presence of an allergic reaction to any food product. In addition, they have an antioxidant effect and prevent the development of tumors.

The synthesis of vitamin C is not complete without the participation of bifidobacteria. In addition, there is information that bifidobacteria help to absorb vitamins D and B, which are necessary for a person to function normally. If there is a deficiency of bifidobacteria, even taking synthetic vitamins of this group will not bring any results.

Lactobacilli

This group of microorganisms is also important for human health. Thanks to their interaction with other inhabitants of the intestine, the growth and development of pathogenic microorganisms is blocked and pathogens of intestinal infections are suppressed.

Lactobacilli are involved in the formation of lactic acid, lysocine, and bacteriocins. This is a great help for the immune system. If there is a deficiency of these bacteria in the intestines, then dysbiosis develops very quickly.

Lactobacilli populate not only the intestines, but also the mucous membranes. So these microorganisms are important for women's health. They maintain the acidity of the vaginal environment and prevent the development of bacterial vaginosis.

Escherichia coli

Not all types of E. coli are pathogenic. Most of them, on the contrary, perform a protective function. The usefulness of the genus E. coli lies in the synthesis of cocilin, which actively resists the bulk of pathogenic microflora.

These bacteria are useful for the synthesis of various groups of vitamins, folic and nicotinic acid. Their role in health should not be underestimated. For example, folic acid is essential for the production of red blood cells and maintaining normal hemoglobin levels.

Enterococci

This type of microorganism colonizes the human intestine immediately after birth.

They help absorb sucrose. Living mainly in the small intestine, they, like other beneficial non-pathogenic bacteria, provide protection against excessive proliferation of harmful elements. At the same time, enterococci are considered to be relatively safe bacteria.

If they begin to exceed permissible limits, various bacterial diseases develop. The list of diseases is very long. Starting from intestinal infections, ending with meningococcal.

Positive effects of bacteria on the body

The beneficial properties of non-pathogenic bacteria are very diverse. As long as there is a balance between the inhabitants of the intestines and mucous membranes, the human body functions normally.

Most bacteria are involved in the synthesis and breakdown of vitamins. Without their presence, B vitamins are not absorbed by the intestines, which leads to disorders of the nervous system, skin diseases, and decreased hemoglobin.

The bulk of undigested food components that reach the large intestine are broken down precisely by bacteria. In addition, microorganisms ensure the constancy of water-salt metabolism. More than half of all microflora is involved in the regulation of the absorption of fatty acids and hormones.

The intestinal microflora forms local immunity. It is here that the bulk of pathogenic organisms are destroyed and the harmful microbe is blocked.

Accordingly, people do not feel bloating and flatulence. An increase in lymphocytes provokes active phagocytes to fight the enemy and stimulate the production of immunoglobulin A.

Beneficial non-pathogenic microorganisms have a positive effect on the walls of the small and large intestines. They maintain a constant level of acidity there, stimulate the lymphoid apparatus, the epithelium becomes resistant to various carcinogens.

Intestinal peristalsis also largely depends on what microorganisms are in it. Suppressing the processes of decay and fermentation is one of the main tasks of bifidobacteria. Many microorganisms develop for many years in symbiosis with pathogenic bacteria, thereby controlling them.

Biochemical reactions that constantly occur with bacteria release a lot of thermal energy, maintaining the overall thermal balance of the body. Microorganisms feed on undigested residues.

Dysbacteriosis

Dysbacteriosis is a change in the quantitative and qualitative composition of bacteria in the human body . In this case, beneficial organisms die, and harmful ones actively reproduce.

Dysbacteriosis affects not only the intestines, but also the mucous membranes (there may be dysbacteriosis of the oral cavity, vagina). The names that will prevail in the analyzes are: streptococcus, staphylococcus, micrococcus.

In normal conditions, beneficial bacteria regulate the development of pathogenic microflora. The skin and respiratory organs are usually under reliable protection. When the balance is disturbed, a person experiences the following symptoms: intestinal flatulence, bloating, abdominal pain, frustration.

Later, weight loss, anemia, and vitamin deficiency may begin. From the reproductive system there is abundant discharge, often accompanied by an unpleasant odor. Irritation, roughness, and cracks appear on the skin. Dysbacteriosis is a side effect after taking antibiotics.

If you notice such symptoms, you should definitely consult a doctor, who will prescribe a set of measures to restore normal microflora. This often requires taking probiotics.

The microbiome, or microbiota, or microflora of a person consists of the entire set of microorganisms that live in the body and on the body. In fact, there are 10 times more bacteria inside our bodies than on our skin. The study of the human microbiome covers the totality of all microbes and the genomes of microbial communities in the human body.

These microbes are found in different places in the human body's ecosystem and perform important functions necessary for our health. For example, gut bacteria allow us to properly digest and absorb nutrients from the foods we eat.

The gene activity of beneficial microbes that colonize the body affects human physiology and protects against. Impaired microbiome activity is associated with the development of a number of autoimmune diseases, including diabetes and fibromyalgia.

Human microbiome

Microscopic organisms that live in the body include archaea, bacteria, fungi, protists and viruses. Microbes begin to colonize our body from the moment we are born. The human microbiota changes in the number and type of microorganisms throughout life, with the number of species increasing from birth to adulthood and decreasing in old age. These germs are unique from person to person and can be affected by certain activities such as hand washing or taking antibiotics. Bacteria are the most numerous microorganisms in the human microbiome.

The human microbiome also includes microscopic animals such as mites. These tiny arthropods commonly colonize the skin.

Skin microbiome

Human skin is inhabited by a number of different microorganisms that live on the surface of the skin, as well as in the glands and hair. Our skin is in constant contact with the external environment and serves as the body's first line of defense against potential infections. Skin microbiota helps prevent pathogens from colonizing the skin. It also helps train our immune system by alerting immune cells to the presence of pathogens and initiating an immune response.

The human skin ecosystem is very diverse, with varying skin layers, acidity levels, temperature, thickness, and exposure to sunlight. Thus, the microbes that live in a particular place on or in the skin are different from the microbes in other parts of the body. For example, the microorganisms that colonize the moist, hot parts of the body (under the arms) are different from those that colonize the dry, cooler surfaces of the skin on the arms and legs. Commensal microorganisms that commonly inhabit our skin include bacteria, viruses, fungi, and microscopic animals such as mites.

Skin-colonizing bacteria thrive in one of three skin types: oily, moist, and dry. The three main types of bacteria inhabiting these skin types include: propionic acid bacteria ( Propionibacterium) - found mainly in fatty areas; corynebacteria ( Corynebacterium) - found in humid areas; staphylococci ( Staphylococcus) - inhabiting dry areas.

Although most of these types of bacteria are not dangerous, they can become harmful to humans under certain conditions. For example, propionibacterium acne ( Propionibacterium acnes) live on oily skin surfaces such as the face, neck and back. When the body produces excess fat, these bacteria multiply at a high rate, which can lead to the development of acne. Other types of bacteria, such as Staphylococcus aureus ( Staphylococcus aureus) and Streptococcus pyogenes ( Streptococcus pyogenes), can cause more serious problems such as septicemia and sore throat.

Not much is known about commensal skin viruses, as research in this area is still limited. Viruses have been found to be found on skin surfaces, sebaceous glands, and within skin bacteria.

Types of fungi that colonize human skin include candidiasis ( Candida), Malassezia ( Malassezia), cryptococcus ( Cryptocoocus), debaryomyces ( Debaryomyces) and microsporia ( Microsporum). As with bacteria, fungi reproduce at an unusually high rate and can cause problematic conditions and diseases. Malassezia fungi can cause dandruff and atopic eczema.

Microscopic animals that inhabit the skin include mites. For example, demodex mites ( Demodex) colonize the face and live inside hair follicles. They feed on sebum, dead cells and even some bacteria.

Gut microbiome

The human gut microbiome is diverse and abundant. It includes trillions of bacteria with thousands of different species. These microbes thrive in the harsh environment of the gut and are actively involved in supporting digestion, normal metabolism, and proper immune function. They help in the digestion of indigestible carbohydrates, the metabolism of bile acids and drugs, and the synthesis of amino acids and many vitamins.

Several intestinal microorganisms produce antimicrobial substances that protect us from pathogenic bacteria. The composition of the gut microbiota is unique to each individual and is constantly changing. It changes with factors such as age, changes in diet, exposure to toxic substances (antibiotics) and changes in health status. Deviations in the composition of commensal microorganisms in the gut have been associated with the development of gastrointestinal diseases such as inflammatory bowel disease, celiac disease and irritable bowel syndrome.

The vast majority of bacteria (about 99%) that live in the intestines are mainly composed of two types: bacteroides ( Bacteroidetes) and Firmicutes ( Firmicutes). Examples of other types of bacteria found in the gut include Proteobacteria (such as Escherichia ( Escherichia), salmonella ( Salmonella) and vibrios ( Vibrio)), actinobacteria ( Actinobacteria) and melainabacteria ( Melainabacteria).

The gut microbiome also contains archaea, fungi and viruses. The most common archaea in the gut are methanogens Methanobrevibacter smithii And Methanosphaera stadtmanae. Types of fungi found in the human intestine include candidiasis ( Candida), Saccharomycetes ( Saccharomyces) and cladospory ( Cladosporium). Changes in the normal composition of intestinal fungi have been linked to the development of diseases such as Crohn's disease and ulcerative colitis. The most common viruses in the gut microbiome are bacteriophages, which infect gut bacteria.

Oral microbiome

The oral microbiome contains millions of microorganisms that usually exist in a mutually beneficial relationship with the host. While most microbes are beneficial, preventing the oral cavity from being colonized by harmful microorganisms, some can become pathogenic under certain conditions.

Bacteria are the most numerous of the oral microorganisms and include streptococci ( Streptococcus), actinomycetes ( Actinomyces), lactobacilli ( Lactobacterium), staphylococci ( Staphylococcus) and propionibacteria ( Propionibacterium). Bacteria protect themselves from stressful conditions in the mouth by producing a sticky substance called biofilm. Biofilm protects bacteria from antibiotics, other microorganisms, chemicals, tooth brushing, or substances harmful to germs. Biofilms of different types of bacteria form dental plaque, which adheres to tooth surfaces and can cause tooth decay.

Oral microbes often interact to benefit each other. For example, bacteria and fungi sometimes coexist in relationships that can be harmful to the host. The bacterium streptococcus mutans ( Streptococcus mutans) and the fungus candida albicans ( Candida albicans), working together, cause serious dental problems, most often found in preschoolers.

Archaea in the oral cavity, include methanogens Methanobrevibacter oralis And Methanobrevibacter smithii. Oral protists include the oral amoeba ( Entamoeba gingivalis) and oral Trichomonas ( Trichomonas lenax). These commensal microorganisms feed on bacteria or food particles and are found in much higher numbers in people with gum disease. Oral viruses are predominantly composed of bacteriophages.

Rice. 12. The photo shows streptoderma in a child.

Rice. 13. The photo shows erysipelas of the lower leg caused by streptococcal bacteria.

Rice. 14. In the photo there is a panaritium.

Rice. 15. The photo shows a carbuncle of the skin of the back.

Staphylococci on the skin

Fungi of the genus Microsporum cause the disease microsporia. The source of infection is cats with trichophytosis; less commonly, the disease is transmitted from dogs. Mushrooms are very stable in the external environment. They live on skin scales and hair for up to 10 years. Children get sick more often, as they are more likely to come into contact with sick stray animals. In 90% of cases, fungi affect vellus hair. Much less often, microsporum affects open areas of the skin.

Rice. 22. Photo of fungi of the genus Microsporum.

Rice. 23. The photo shows scalp fungus (microsporia). On the scalp, the lesion is covered with asbestos scales and crusts.

The disease is highly contagious (infectious). The person himself and his things are the source of infection. With this form of trichophytosis, open areas of the body are also affected, but with a prolonged course, the skin of the buttocks and knees can be affected.

Rice. 24. The photo shows scalp fungus (trichophytia).

Tinea versicolor is a fairly common disease. The disease is more common in young and middle-aged people. It is believed that the cause of the disease is a change in the chemical composition of sweat due to excessive sweating. Diseases of the stomach and intestines, endocrine system, neurovegetative pathology and immunodeficiency are the trigger for the development of pityriasis versicolor.

Fungi infect the skin of the body. Lesions are often found on the skin of the chest and abdomen. The skin of the head, extremities and groin areas is much less frequently affected.

Rice. 25. The photo shows the skin of the back.

Rice. 26. The photo shows the fungi Malassezia furfur (growth of colonies on a nutrient medium).

Rice. 27. The photo shows seborrheic dermatitis. The scalp is affected.

Fungi Pityrosporum orbiculare (P. orbiculare) infect the skin of the body. Pathogens concentrate in places of greatest accumulation of sebum, which is produced by the sebaceous glands. The causative agents of seborrheic dermatitis use sebum in the process of their life. The rapid growth of fungi is provoked by neurogenic, hormonal and immune factors.

With candidiasis, changes appear primarily on the skin of large and small folds of the body. As the disease develops, the lesions spread to the skin of the body.

Somewhat less frequently, lesions are observed on the skin of the palms and soles. Fungi of the genus Candida affect the mucous membranes of external and internal organs. Capable of causing systemic mycoses.

The disease often affects infants. Patients with diabetes mellitus and severe somatic pathology are at risk for candidiasis.
The disease lasts a long time. Recurs often.

Rice. 28. Photo of fungi of the genus Candida (Candida albicans). View through a microscope.

Rice. 31. The photo shows a colony of mold fungi.

Bacteria in the intestines

The human body contains from 500 to 1000 different types of bacteria or trillions of these amazing residents, which amounts to up to 4 kg of total weight. Up to 3 kilograms of microbial bodies are found only in the intestines. The rest of them are found in the genitourinary tract, on the skin and other cavities of the human body.

The human body is inhabited by both beneficial and harmful pathogenic bacteria. The existing balance between the human body and bacteria has been refined over centuries. When immunity decreases, “bad” bacteria cause great harm to the human body. Some diseases make it difficult to replenish the body with “good” bacteria.

Microbes fill the body of a newborn from the first minutes of his life and finally form the composition of the intestinal microflora by the age of 10-13 years.

Up to 95% of the microbial population of the large intestine consists of bifidobacteria and bacteroides. Up to 5% are lactic acid bacilli, staphylococci, enterococci, fungi, etc. The composition of this group of bacteria is always constant and numerous. It carries out basic functions. 1% are opportunistic bacteria (pathogenic bacteria). Bifidobacteria, E. coli, acidophilus bacilli and enterococci suppress the growth of opportunistic flora.

In diseases that reduce the body's immunity, intestinal diseases, long-term use of antibacterial drugs and in the absence of lactose in the human body, when the sugar contained in milk is not digested and begins to ferment in the intestines, changing the acid balance of the intestines, a microbial imbalance occurs - dysbiosis (dysbiosis). , enterococci, clostridia, staphylococci, yeast-like fungi and proteus begin to multiply intensively. Pathological forms begin to appear among them.

Dysbacteriosis is characterized by the death of “good” bacteria and increased growth of pathogenic microorganisms and fungi. The processes of rotting and fermentation begin to prevail in the intestines. This is manifested by diarrhea and bloating, pain, loss of appetite, and then weight, children begin to lag behind in development, anemia and hypovitaminosis develop.

Food poisoning suddenly affects a person or group of people who have eaten food, often quite benign in appearance. And despite the unchanged taste, color and smell, the dish that caused the poisoning contains a huge number of microbes that have multiplied in it and their toxins (poisons). Such microbial poisonings account for 90 percent of all food poisonings. Some of them are easy, others end tragically. Bacterial food poisoning is especially difficult for children, the elderly, and those suffering from chronic diseases of the digestive system.

First place in prevalence among bacterial food Salmonella infections are currently the main cause of poisoning. They affect not only people, but also animals: cattle, pigs, sheep, goats, horses, ducks, chickens, geese, turkeys—the main source of this infection. Animals become infected from each other if they are kept in a common pen. It happens that sick ducks or geese contaminate the water in the pond, and cows and horses drink it and also get sick with salmonellosis. The meat of sick animals is literally contaminated with salmonella. They also end up in animal milk and poultry eggs. Moreover, waterfowl eggs (ducks, geese) are especially dangerous, since salmonella is found not only on the outside of the shell, but also inside.

In addition to the so-called intravital contamination of meat, eggs, milk of sick animals and birds, secondary contamination of these products sometimes occurs after the slaughter of livestock or poultry. This happens when cutting a carcass, its improper storage and transportation, when it comes into contact with the meat of sick animals and birds. Meat and meat products are frequent (75-85 percent) culprits of food poisoning of a sapmonella nature.

Salmonella at home fall on various products when the housewife uses dishes, a meat grinder, knives, and a cutting board, first for processing raw meat and then for cooked foods. Improper storage of prepared foods in the refrigerator can also lead to salmonella contamination: in unclosed containers next to raw meat and other raw foods.

Dishes made from minced meat, especially jelly, pose a great danger.
The most powerful of all known bacterial poisons secretes the microbe botulinus, which is widespread in nature. It is found in the soil, in the intestines of fish and animals, and forms spores. The transformation of botulinus spores into microbes, their reproduction and destruction, and therefore the release of toxin, is possible, only without access to oxygen. That is why canned food creates the most favorable conditions for the germination of spores and the proliferation of microbes. Botulinus is unstable in the external environment, it dies at boiling temperatures, its reproduction is delayed in an acidic environment, but its spores are very resistant to heat, the action of chemicals and bactericidal substances.

They tolerate boiling for several hours. Preparing canned food at home in hermetically sealed jars does not destroy the spores. The only way to destroy them— heating in an autoclave at a temperature of 120 degrees and a certain pressure, which is only possible in the industrial production of canned food.

Among homemade canned foods, the most dangerous are mushrooms in hermetically sealed jars. This is due to the fact that it is difficult to thoroughly wash mushrooms from soil particles, which can also include botulinus spores. The following homemade canned foods are also the culprits of severe poisoning: eggplant and squash caviar, stuffed peppers, cucumbers, purslane, dill and parsley, apricot compote, which contain a small amount of natural acid.

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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 such “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 to 2H2O), iron (Fe2+ to Fe3+) or sulfur (2S + 3O2 + 2H2O to 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-legume 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 use of these living laboratories has received a powerful new impetus. 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. In order for such water treatment plants to 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 require 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 .