Bacteria arises. Positive effects of bacteria on the body

Which do not have a core. Most bacteria are heterotrophs, but there are also autotrophs. They reproduce by division. When unfavorable conditions occur, some bacteria form spores.

Bacteria can only be seen through a microscope, which is why they are called microorganisms. Microorganisms are studied by the science of microbiology. The branch of microbiology that studies bacteria is called bacteriology.

The first to see and describe bacteria was the Dutch naturalist Anthony van Leeuwen Hoek (1632-1723). He learned to grind glass and make lenses. Leeuwenhoek made more than 400 microscopes and discovered the world of microscopic organisms - bacteria and protists.

When we hear about bacteria, we most often imagine a sore throat or gums, despite the fact that only a small part of bacteria cause disease. Most of these organisms perform other important functions.

We begin to come into contact with bacteria from the first hours of life. Many of them constantly live on the surface of human skin. There are even more of them on the teeth, gums, tongue and walls of the oral cavity. There are more bacteria in your mouth than there are people on Earth! But the largest number of them lives in the intestines - up to 5 kg in an adult.

Bacteria are found everywhere: in water, soil, air, in plant tissues, in the bodies of animals and humans. They live where they find enough food, moisture and favorable temperatures (10-40 ° C). Most of them require oxygen. There are also bacteria that live in hot springs (with a temperature of 60-90 ° C), extremely salty bodies of water, in volcanoes, deep in the oceans, where it does not penetrate sunlight. Even in the coldest regions (Antarctica) and high mountains Bacteria live on the tops.

Found in different places different quantity bacteria. There are fewer of them in the air, especially in natural conditions. And in crowded places, such as cinemas, train stations, and classrooms, there are much more of them. Therefore, it is necessary to ventilate the premises frequently.

In river waters, especially near large cities, there can be a lot of bacteria - up to several hundred thousand per 1 mm3. Therefore, you should not drink raw water from open reservoirs. There are a lot of bacteria in the water of the seas and oceans.

There are even more bacteria in the soil - up to 100 million per 1 g of humus (fertile soil layer).

Bacteria are very small organisms. The largest bacteria can be seen under a light microscope.

To get acquainted with the smallest ones, an electron microscope is required (Fig. 7).

Most of the bacteria that inhabit our home and our body are in the form of balls, sticks and spirals. Spherical bacteria are called cocci, rod-shaped bacteria are called bacilli, and spiral-shaped bacteria are called spirilla (Fig. 9). Some bacteria form chains, located close to each other.

Consider the structure of a bacterial cell in Figure 10. It includes cytoplasm, surrounded by a cytoplasmic membrane and a cell membrane (cell wall). The shell gives the bacterium a certain shape and serves as protection from unfavorable conditions.

Additional protection for many bacteria will be provided by the mucus layer located on the outside of the shell. The surface of the bacterial cell is covered with numerous villi, which are hollow outgrowths of the cytoplasmic membrane. Some bacteria have one or more filamentous flagella.

The main difference between bacteria is the absence of a nucleus, i.e. they are prokaryotes.

It is on this basis that they are separated into a separate kingdom. The nuclear material of bacteria is the bacterial chromosome: it carries hereditary information.

Most bacteria are heterotrophs. They consume ready-made organic substances. Their food consists of living and dead organisms, human food products, wastewater, etc.

Saprotrophs

Some heterotrophic bacteria use organic substances from dead bodies or secretions of living organisms. These are saprotrophs (from the Greek sapros - rotten and trophos - nutrition).

There are also autotrophic bacteria. They are capable of forming organic substances from inorganic ones (carbon dioxide, water, hydrogen sulfide, etc.). Autotrophic photosynthetic bacteria have bacterial chlorophyll in their cells, with which they form organic substances under the influence of solar energy.

Cyanobacteria

An example of autotrophic bacteria is cyanobacteria. They make their own food from carbon dioxide and water when exposed to sunlight. At the same time, they release oxygen, enriching their habitat.

Bacteria reproduce by division. In this case, two mother cells are formed from one mother cell daughter cells, similar to the mother's. At favorable conditions(sufficient nutrition, humidity and temperature from 10 to 30 ° C) bacteria can divide every 20-30 minutes, so their number increases very quickly. Material from the site

If bacteria are cultivated (grown) on a nutrient medium under favorable conditions, they multiply very quickly and form colonies of up to 4 billion cells. Colonies of bacteria of certain species have characteristic outlines and colors (Fig. 8). By the type of colonies, you can determine the presence of certain bacteria in a particular material.

Some bacteria move using flagella. The base of the flagellum rotates, and it seems to be screwed into the medium, ensuring the movement of the bacterium. Most bacteria move passively: some with the help of air currents, others with the flow of water. This is how they are distributed.

Under unfavorable conditions (lack of food, moisture, sudden temperature fluctuations), bacteria can turn into spores. The cytoplasm near the bacterial chromosome becomes denser. A very strong shell is formed around it. Spores formed in this way can exist for hundreds of years (Fig. 11).

Everyone knows that bacteria are the most ancient look living creatures that inhabit our planet. The first bacteria were the most primitive, but as our earth changed, so did the bacteria. They are present everywhere, in water, on land, in the air we breathe, in food, in plants. Just like people, bacteria can be good and bad.

Beneficial bacteria are:

• Lactic acid or lactobacilli. One of these good bacteria is lactic acid bacteria. This is a rod-shaped type of bacteria that lives in dairy and fermented milk products. These bacteria also inhabit the human oral cavity, intestines, and vagina. The main benefit of these bacteria is that they produce lactic acid as a fermentation, thanks to which we get yogurt, kefir, fermented baked milk from milk, in addition, these products are very useful for humans. In the intestines, they play the role of cleansing the intestinal environment from bad bacteria.
• Bifidobacteria. Bifidobacteria are found mainly in the gastrointestinal tract, just like lactic acid bacteria are capable of producing lactic acid and acetic acid, due to which these bacteria control the growth of pathogenic bacteria, thereby regulating the pH level in our intestines. Various varieties of bifidobacteria help get rid of constipation, diarrhea, and fungal infections.
• Escherichia coli. The human intestinal microflora consists of most microbes of the Escherichia coli group. They promote good digestion and are also involved in certain cellular processes. But some varieties of this stick can cause poisoning, diarrhea, and kidney failure.
• Streptomycetes. The habitat of streptomycetes is water, decomposing compounds, soil. Therefore, they are especially useful for the environment, because... Many processes of decomposition and combinations are carried out with them. In addition, some of these bacteria are used in the production of antibiotics and antifungal drugs.

Harmful bacteria are:

• Streptococci. Chain-shaped bacteria, which, when entering the body, are the causative agents of many diseases, such as tonsillitis, bronchitis, otitis media and others.
• Plague stick. A rod-shaped bacterium that lives in small rodents causes terrible diseases such as plague or pneumonia. Plague is a terrible disease that can destroy entire countries, and it has been compared to biological weapons.
• Helicobacter pylori. The habitat of Helicobacter pylori is the human stomach, but in some people the presence of these bacteria causes gastritis and ulcers.
• Staphylococcus. The name staphylococcus comes from the fact that the shape of the cells resembles a bunch of grapes. For humans, these bacteria cause severe diseases with intoxication and purulent formations. No matter how terrible bacteria are, humanity has learned to survive among them thanks to vaccination.

True, bacteria), microorganisms with a prokaryotic type of cell structure: their genetic apparatus is not enclosed in a cell nucleus isolated by a membrane.

Sizes and shapes of cells. Most bacteria are single-celled organisms with a size of 0.2-10.0 microns. Among the bacteria, there are also “dwarfs”, the so-called nanobacteria (about 0.05 microns), and “giants”, for example, bacteria of the genera Achromatium and Macromonas (length up to 100 microns), an inhabitant of the intestines of the surgeon fish Epulopiscium fishelsoni (length up to 600 microns) and Thiomargarita namibiensis isolated from coastal sea waters of Namibia and Chile (up to 800 µm). Most often, the bacterial cell has a rod-shaped, spherical (cocci) or convoluted (vibrios, spirilla and spirochetes) shape. Species with triangular, square, stellate and flat (plate-shaped) cells have been found. Some bacteria contain cytoplasmic projections called prosteks. Bacteria can be single, form pairs, short and long chains, clusters, form packets of 4, 8 or more cells (sarcinae), rosettes, networks and mycelium (actinomycetes). Multicellular forms are also known, forming straight and branching trichomes (microcolonies). Both motile and nonmotile bacteria are found. The former most often move with the help of flagella, sometimes by sliding cells (myxobacteria, cyanobacteria, spirochetes, etc.). A “jumping” movement is also known, the nature of which is not clear. For mobile forms, the phenomena of active movement in response to the action of physical or chemical factors are described.

Chemical composition and structure of cells. A bacterial cell is usually 70-80% water. In the dry residue, protein accounts for 50%, cell wall components 10-20%, RNA 10-20%, DNA 3-4% and lipids 10%. On average, the amount of carbon is 50%, oxygen 20%, nitrogen 14%, hydrogen 8%, phosphorus 3%, sulfur and potassium 1% each, calcium and magnesium 0.5% each and iron 0.2%.

With few exceptions (mycoplasmas), bacterial cells are surrounded by a cell wall, which determines the shape of the bacterium and performs mechanical and important functions. physiological functions. Its main component is the complex biopolymer murein (peptidoglycan). Depending on the characteristics of the composition and structure of the cell wall, bacteria behave differently when stained according to the method of H. C. Gram (the Danish scientist who proposed the staining method), which served as the basis for dividing bacteria into gram-positive, gram-negative and those lacking a cell wall (for example , mycoplasma). The former are distinguished by a high (up to 40 times) murein content and a thick wall; in gram-negatives it is significantly thinner and covered on the outside with an outer membrane consisting of proteins, phospholipids and lipopolysaccharides and, apparently, involved in the transport of substances. Many bacteria have villi (fimbriae, pili) and flagella on their surface that enable their movement. Often the cell walls of bacteria are surrounded by mucous capsules of varying thickness, formed mainly by polysaccharides (sometimes glycoproteins or polypeptides). In a number of bacteria, so-called S-layers (from English surface) were also found, lining the outer surface of the cell membrane with evenly packed protein structures of regular shape.

The cytoplasmic membrane, which separates the cytoplasm from the cell wall, serves as the osmotic barrier of the cell and regulates the transport of substances; the processes of respiration, nitrogen fixation, chemosynthesis, etc. are carried out in it. It often forms invaginations - mesosomes. The biosynthesis of the cell wall, sporulation, etc. are also associated with the cytoplasmic membrane and its derivatives. Flagella and genomic DNA are attached to it.

The bacterial cell is organized quite simply. In the cytoplasm of many bacteria there are inclusions represented by various kinds bubbles (vesicles) formed as a result of invagination of the cytoplasmic membrane. Phototrophic, nitrifying and methane-oxidizing bacteria are characterized by a developed network of cytoplasmic membranes in the form of undivided vesicles, reminiscent of the grana of eukaryotic chloroplasts. The cells of some water-dwelling bacteria contain gas vacuoles (aerosomes) that act as density regulators; In many bacteria, inclusions of reserve substances are found - polysaccharides, poly-β-hydroxybutyrate, polyphosphates, sulfur, etc. Ribosomes are also present in the cytoplasm (from 5 to 50 thousand). Some bacteria (for example, many cyanobacteria) have carboxysomes - bodies that contain an enzyme involved in CO 2 fixation. The so-called parasporal bodies of some spore-forming bacteria contain a toxin that kills insect larvae.

The bacterial genome (nucleoid) is represented by a circular DNA molecule, which is often called the bacterial chromosome. The bacterial genome is characterized by the combination of many functionally related genes into so-called operons. In addition, the cell may contain extrachromosomal genetic elements - DNA plasmids, which carry several genes useful for bacteria (including antibiotic resistance genes). It can exist autonomously or be temporarily included in the chromosome. But sometimes, as a result of mutations, this DNA loses its ability to leave the chromosome and becomes a permanent component of the genome. The appearance of new genes can also be due to genetic transfer as a result of unidirectional transfer of DNA from a donor cell to a recipient cell (an analogue of the sexual process). Such transfer can occur through direct contact of two cells (conjugation), with the participation of bacteriophages (transduction), or by the entry of genes into the cell from the external environment without intercellular contact. All this is of great importance for the microevolution of bacteria and their acquisition of new properties.

Reproduction. Most bacteria reproduce by fission in two, less often by budding, and some (for example, actinomycetes) - with the help of exospores or fragments of mycelium. There is a known method of multiple division (with the formation of small reproductive cells-baeocytes in a number of cyanobacteria). Multicellular prokaryotes can reproduce by detaching one or more cells from the trichomes. Some bacteria are characterized by a complex development cycle, during which the morphology of cells can change and resting forms can form: cysts, endospores, akinetes. Myxobacteria are capable of forming fruiting bodies, often of bizarre configurations and colors.

A distinctive feature of bacteria is their ability to reproduce quickly. For example, the doubling time of Escherichia coli cells is 20 minutes. It is estimated that the progeny of one cell, in the case of unlimited growth, in just 48 hours would exceed the mass of the Earth by 150 times.

Living conditions. Bacteria have adapted to different living conditions. They can develop in a temperature range from -5 (and below) to 113 °C. Among them are: psychrophiles, growing at temperatures below 20 °C (for Bacillus psichrophilus, for example, the maximum growth temperature is -10 °C), mesophiles (growth optimum at 20-40 °C), thermophiles (50-60 °C), extreme thermophiles (70 °C) and hyperthermophiles (80 °C and above). Spores of certain types of bacteria can withstand short-term heating to 160-180 ° C and long-term cooling to -196 ° C and below. Some bacteria are extremely resistant to ionizing radiation and even live in the cooling water of nuclear reactors (Deinococcus radiodurans). A number of bacteria (barophiles, or piezophiles) tolerate hydrostatic pressure up to 101 thousand kPa, and certain species do not grow at pressures below 50 thousand kPa. At the same time, there are bacteria that cannot withstand even a slight increase atmospheric pressure. Most types of bacteria do not develop if the concentration of salts (NaCl) in the medium exceeds 0.5 mol/l. Optimal conditions for the development of moderate and extreme halophiles are observed in environments with NaCl concentrations of 10 and 30%, respectively; they can grow even in saturated salt solutions.

As a rule, bacteria prefer neutral environmental conditions (pH about 7.0), although there are both extreme acidiphiles, capable of growth at pH 0.1-0.5, and alkaliphiles, developing at pH up to 13.0.

The vast majority of bacteria studied are aerobes. Some of them can grow only at low concentrations of O 2 - up to 1.0-5.0% (microaerophiles). Facultative anaerobes grow both in the presence of O 2 and in its absence; they are able to switch metabolism from aerobic respiration to fermentation or anaerobic respiration (enterobacteria). The growth of aerotolerant anaerobes is not inhibited in the presence small quantity O 2, because they do not use it in the process of life (for example, lactic acid bacteria). For strict anaerobes, even traces of O 2 in the habitat are destructive.

Many bacteria survive unfavorable environmental conditions, forming dormant forms.

Most bacteria that utilize nitrogen compounds, as a rule, use its reduced forms (most often ammonium salts), some require ready-made amino acids, while others also assimilate its oxidized forms (mainly nitrates). A significant number of free-living and symbiotic bacteria are capable of fixing molecular nitrogen (see the article Nitrogen fixation). Phosphorus, which is part of nucleic acids and other cell compounds, is obtained by bacteria mainly from phosphates. The source of sulfur necessary for the biosynthesis of amino acids and some enzyme cofactors is most often sulfates; Some types of bacteria require reduced sulfur compounds.

Taxonomy. There is no officially accepted classification of bacteria. Initially used for these purposes artificial classification, based on the similarity of their morphological and physiological characteristics. A more advanced phylogenetic (natural) classification unites related forms based on their common origin. This approach became possible after the choice of the 16S rRNA gene as a universal marker and the advent of methods for determining and comparing nucleotide sequences. The gene encoding 16S rRNA (part of the small subunit of the prokaryotic ribosome) is present in all prokaryotes and is characterized by a high degree of conservation of the nucleotide sequence and functional stability.

The most commonly used is the classification published in the periodical publication of the determinant Bergi (Bergi); see also the website on the Internet - http://141. 150.157.117:8080/prokPUB/index.htm. According to one of existing systems organisms, bacteria together with archaea constitute the kingdom of prokaryotes. Many researchers consider them as a domain (or superkingdom), along with the domains (or superkingdoms) of archaea and eukaryotes. Within the domain, the largest taxa of bacteria are the phyla: Proteobacteria, including 5 classes and 28 orders; Actinobacteria (5 classes and 14 orders) and Firmicutes (3 classes and 9 orders). In addition, taxonomic categories of lower rank are distinguished: families, genera, species and subspecies.

According to modern concepts, one species includes strains of bacteria in which the nucleotide sequences in the genes encoding 16S rRNA coincide by more than 97%, and the level of homology of nucleotide sequences in the genome exceeds 70%. No more than 5,000 species of bacteria have been described, which represent only a small part of those inhabiting our planet.

Bacteria actively participate in biogeochemical cycles on our planet (including the cycle of most chemical elements). The modern geochemical activity of bacteria is also global in nature. For example, out of 4.3 10 10 tons (gigatons) of organic carbon fixed during photosynthesis in the World Ocean, about 4.0 10 10 tons are mineralized in the water column, and 70-75% of them are bacteria and some other microorganisms , and the total production of reduced sulfur in ocean sediments reaches 4.92·10 8 tons per year, which is almost three times the total annual production of all types of sulfur-containing raw materials used by humanity. The bulk of the greenhouse gas methane entering the atmosphere is produced by bacteria (methanogens). Bacteria are a key factor in soil formation, oxidation zones of sulfide and sulfur deposits, the formation of iron and manganese sedimentary rocks, etc.

Some bacteria cause serious diseases in humans, animals and plants. They often cause damage to agricultural products, destruction of underground parts of buildings, pipelines, metal structures of mines, underwater structures, etc. Studying the characteristics of the life activity of these bacteria makes it possible to develop effective ways to protect against the damage they cause. At the same time, the positive role of bacteria for humans cannot be overestimated. With the help of bacteria, wine, dairy products, starter cultures and other products, acetone and butanol, acetic and citric acid, some vitamins, a number of enzymes, antibiotics and carotenoids; bacteria are involved in the transformation of steroid hormones and other compounds. They are used to produce protein (including enzymes) and a number of amino acids. The use of bacteria to process agricultural waste into biogas or ethanol makes it possible to create fundamentally new renewable energy resources. Bacteria are used to extract metals (including gold), increase oil recovery (see articles Bacterial leaching, Biogeotechnology). Thanks to bacteria and plasmids, the development of genetic engineering. The study of bacteria played a huge role in the development of many areas of biology, medicine, agronomy, etc. Their importance in the development of genetics is great, because they have become a classic object for studying the nature of genes and the mechanisms of their action. The establishment of metabolic pathways for various compounds, etc., is associated with bacteria.

The potential of bacteria is practically inexhaustible. Deepening knowledge about their life activities opens up new directions for the effective use of bacteria in biotechnology and other industries.

Lit.: Schlegel G. General microbiology. M., 1987; The Prokaryotes: Electronic release 3.0-3.17-. N. Y., 1999-2004-; Zavarzin G. A., Kolotilova N. N. Introduction to natural history microbiology. M., 2001; Madigan M. T., Martinko J., Parker J. Brock biology of microorganisms. 10th ed. Upper Saddle River, 2003; Ecology of microorganisms. M., 2004.

At this very moment, man, when you are reading these lines, you are benefiting from the work of bacteria. From the oxygen we breathe in to the nutrients our stomachs extract from our food, we have bacteria to thank for thriving on this planet. In our body there are about ten times more microorganisms, including bacteria, than our own cells. Essentially, we are more microbes than people.

It's only recently that we've begun to understand a little about microscopic organisms and their impact on our planet and health, but history shows that centuries ago our ancestors were already harnessing the power of bacteria to ferment foods and drinks (whoever heard of bread and beer?).

In the 17th century, we began to study bacteria directly in our bodies in close connection with us - in the mouth. Antoni van Leeuwenhoek's curiosity led to the discovery of bacteria when he examined a plaque between his own teeth. Van Leeuwenhoek waxed poetic about the bacteria, describing the bacterial colony on his teeth as “a little white substance, like hardened dough.” Placing the sample under a microscope, van Leeuwenhoek saw that the microorganisms were moving. So they are alive!

You should know that bacteria have played a critical role on Earth, being key to the creation of breathable air and the biological richness of the planet we call home.

In this article, we will provide you with an overview of these tiny but very influential microorganisms. We'll look at the good, the bad, and the downright bizarre ways that bacteria shape human and environmental history. First, let's look at how bacteria differ from other types of life.

Bacteria Basics

Well, if bacteria are invisible to the naked eye, how can we know so much about them?

Scientists have developed powerful microscopes to look at bacteria - which range in size from one to a few microns (millionths of a meter) - and figure out how they relate to other life forms, plants, animals, viruses and fungi.

As you may know, cells are the building blocks of life, from the tissues of our body to the tree that grows outside our window. Humans, animals and plants have cells with genetic information contained in a membrane called the nucleus. These types of cells, called eukaryotic cells, have special organelles, each of which performs unique work, helping the cell work.

Bacteria, however, do not have a nucleus, and their genetic material (DNA) floats freely inside the cell. These microscopic cells have no organelles and have other methods of reproduction and transfer of genetic material. Bacteria are considered prokaryotic cells.

Do bacteria survive in an environment with or without oxygen?

Their shape: rods (bacillus), circles (cocci) or spirals (spirillum)

Are the bacteria gram-negative or gram-positive, that is, do they have an outer protective membrane that prevents staining of the cell interior?

How bacteria move around and explore their environment (many bacteria have flagella, tiny whip-like structures that allow them to move around in their environment)

Microbiology - the study of all types of microbes, including bacteria, archaea, fungi, viruses and protozoa - distinguishes bacteria from their microbial cousins.

Bacteria-like prokaryotes, now classified as archaea, were once together with bacteria, but as scientists learned more about them, they gave bacteria and archaea their own categories.

Microbial nutrition (and miasma)

Like people, animals and plants, bacteria need food to survive.

Some bacteria - autotrophs - use basic resources such as sunlight, water and chemical substances from the environment to create food (think of cyanobacteria, which have been converting sunlight into oxygen for 2.5 million years). Other bacteria are called heterotrophs by scientists because they get their energy from existing organic matter as food (for example, dead leaves on forest floors).

The truth is that what may be tasty to bacteria will be disgusting to us. They have evolved to absorb all types of products, from oil spills and nuclear byproducts to human waste and decomposition products.

But a bacteria's affinity for a particular food source could benefit society. For example, art experts from Italy turned to bacteria that can eat excess layers of salt and glue, reducing the durability of priceless works of art. The ability of bacteria to process organic matter is also very beneficial for the Earth, both in soil and in water.

From daily experience, you are well aware of the odor caused by bacteria consuming the contents of your trash can, processing leftover food and emitting its own gaseous by-products. However, this is not all. You can also blame bacteria for causing those awkward moments when you pass gas yourself.

One big family

Bacteria grow and form colonies when given the chance. If food and environmental conditions are favorable, they multiply and form sticky clumps called biofilms to survive on different surfaces- from rocks to the teeth of your mouth.

Biofilms have their pros and cons. On the one hand, they are mutually beneficial to natural objects (mutualism). On the other hand, they can be a serious threat. For example, doctors who treat patients with medical implants and devices have serious concerns about biofilms because they provide real estate for bacteria. Once colonized, biofilms can produce byproducts that are toxic—and sometimes fatal—to humans.

Like people in cities, cells in a biofilm communicate with each other, exchanging information about food and potential danger. But instead of calling neighbors on the phone, bacteria send notes using chemicals.

Also, bacteria are not afraid to live on their own. Some species have developed interesting ways to survive in harsh conditions. When there is no more food and conditions become unbearable, bacteria preserve themselves by creating a hard shell, an endospore, which puts the cell into a state of dormancy and preserves the genetic material of the bacterium.

Scientists find bacteria in such time capsules that were stored for 100 or even 250 million years. This suggests that the bacteria can self-store for a long time.

Now that we know what opportunities colonies provide to bacteria, let's figure out how they get there - through division and reproduction.

Bacteria reproduction

How do bacteria create colonies? Like other life forms on Earth, bacteria need to replicate themselves in order to survive. Other organisms do this through sexual reproduction, but not bacteria. But first, let's discuss why diversity is good.

Life undergoes natural selection, or the selective forces of a certain environment allow one type to flourish and reproduce more than another. You may remember that genes are the machinery that instructs a cell what to do and determines what color your hair and eyes will be. You get genes from your parents. Sexual reproduction leads to mutations, or random changes in DNA, which creates diversity. The more genetic diversity there is, the greater the chance that an organism will be able to adapt to environmental constraints.

For bacteria, reproduction does not depend on meeting the right microbe; they simply copy their own DNA and divide into two identical cells. This process, called binary fission, occurs when one bacterium divides into two, copying DNA and passing it on to both parts of the divided cell.

Since the resulting cell will ultimately be identical to the one from which it was born, this method of propagation is not the best for creating a diverse gene pool. How do bacteria acquire new genes?

It turns out that bacteria use a clever trick: horizontal gene transfer, or the exchange of genetic material without reproducing. There are several ways that bacteria use to do this. One method involves collecting genetic material from the environment outside the cell - from other microbes and bacteria (through molecules called plasmids). Another way is viruses, which use bacteria as a home. When viruses infect a new bacterium, they leave the genetic material of the previous bacterium in the new one.

The exchange of genetic material gives bacteria the flexibility to adapt, and they adapt if they sense stressful changes in the environment, such as food shortages or chemical changes.

Understanding how bacteria adapt is extremely important for fighting them and creating antibiotics for medicine. Bacteria can exchange genetic material so frequently that sometimes treatments that worked before no longer work.

No high mountains, no great depths

If you ask the question “where are the bacteria?”, it is easier to ask “where are there no bacteria?”

Bacteria are found almost everywhere on Earth. It is impossible to imagine the number of bacteria on the planet at any one time, but some estimates put their number (bacteria and archaea together) at 5 octillion - a number with 27 zeros.

Classifying bacterial species is extremely difficult for obvious reasons. There are now approximately 30,000 officially identified species, but the knowledge base is constantly growing, and there are opinions that we are just the tip of the iceberg of all types of bacteria.

The truth is that bacteria have been around for a very long time. They produced some of the oldest fossils, dating back 3.5 billion years. Scientific research suggests that cyanobacteria began creating oxygen approximately 2.3-2.5 billion years ago in the world's oceans, saturating the Earth's atmosphere with the oxygen we breathe to this day.

Bacteria can survive in the air, water, soil, ice, heat, on plants, in the intestines, on the skin - everywhere.

Some bacteria are extremophiles, meaning they can withstand extreme conditions where it is either very hot or cold, or there is no nutrients and the chemicals we commonly associate with life. Researchers have discovered such bacteria in Mariana Trench, the deepest point on Earth at the bottom of the Pacific Ocean, near hydrothermal vents in water and ice. There are also bacteria that love high temperature- such, for example, paint the opalescent pool in Yellowstone National Park.

Bad (for us)

While bacteria make important contributions to human and planetary health, they also have a dark side. Some bacteria can be pathogenic, meaning they cause illness and disease.

Throughout human history, certain bacteria have (understandably) gotten a bad rap, causing panic and hysteria. Take the plague, for example. The bacterium that causes the plague, Yersinia pestis, not only killed more than 100 million people, but may have contributed to the collapse of the Roman Empire. Before the advent of antibiotics, drugs that help fight bacterial infections, they were very difficult to stop.

Even today, these pathogenic bacteria seriously scare us. Thanks to the development of resistance to antibiotics, bacteria that cause anthrax, pneumonia, meningitis, cholera, salmonellosis, tonsillitis and other diseases that still remain close to us always pose a danger to us.

This is especially true for Staphylococcus aureus, the bacterium responsible for staphylococcal infections. This “superbug” causes numerous problems in clinics, since patients often contract this infection when implanting medical implants and catheters.

We've already talked about natural selection and how some bacteria produce a variety of genes that help them cope with environmental conditions. If you have an infection and some of the bacteria in your body are different from others, antibiotics may affect most of the bacterial population. But those bacteria that survive will develop resistance to the drug and remain, waiting for the next chance. Therefore, doctors recommend completing the course of antibiotics to the end, and in general using them as rarely as possible, only as a last resort.

Biological weapons are another frightening aspect of this conversation. Bacteria can be used as a weapon in some cases, notably anthrax was used at one time. In addition, not only people suffer from bacteria. A separate species, Halomonas titanicae, has shown an appetite for the sunken ocean liner Titanic, eating away at the metal of the historic ship.

Of course, bacteria can cause more than just harm.

Heroic bacteria

Let's explore the good side of bacteria. After all, these microbes gave us delicious foods like cheese, beer, sourdough and other fermented elements. They also improve human health and are used in medicine.

Individual bacteria can be thanked for shaping human evolution. Science is collecting more and more data about microflora - microorganisms that live in our bodies, especially in digestive system and intestines. Research shows that bacteria, new genetic materials, and the diversity they bring into our bodies allow humans to adapt to new food sources that have not been exploited before.

Let's look at it this way: by lining the surface of your stomach and intestines, bacteria “work” for you. When you eat, bacteria and other microbes help you break down and extract nutrients from your food, especially carbohydrates. The more diverse the bacteria we consume, the more diversity our bodies gain.

Although our knowledge of our own microbes is very limited, there is reason to believe that the absence of certain microbes and bacteria in the body may be associated with human health, metabolism and susceptibility to allergens. Preliminary studies in mice suggest that metabolic diseases like obesity are associated with a diverse and healthy microbiota, rather than our prevailing “calories in, calories out” mentality.

The possibilities of introducing certain microbes and bacteria into the human body, which can provide certain benefits, are now being actively explored, but at the time of writing general recommendations on their use have not yet been established.

In addition, bacteria played an important role in the development of scientific thought and human medicine. Bacteria played a leading role in the development of Koch's 1884 postulates, which led to the general understanding that disease is caused by a specific type of microbe.

Researchers studying bacteria accidentally discovered penicillin, an antibiotic that saved many lives. Also, quite recently, in connection with this, an easy way to edit the genome of organisms was discovered, which could revolutionize medicine.

In fact, we are just beginning to understand how to benefit from our cohabitation with these little friends. In addition, it is not clear who is the true owner of the Earth: people or microbes.