Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.
Bacteria
Bacteria belong to prokaryotic organisms that do not have nuclear membranes, plastids, mitochondria and other membrane organelles. They are characterized by the presence of one circular DNA. The size of bacteria is quite small, 0.15-10 microns. Based on the shape of the cells, they can be divided into three main groups: spherical , or cocci , rod-shaped And crimped . Bacteria, although they belong to prokaryotes, have a rather complex structure.
Structure of bacteria
The bacterial cell is covered with several outer layers. The cell wall is essential for all bacteria and is the main component of the bacterial cell. The bacterial cell wall gives shape and rigidity and, in addition, performs a number of important functions:
- protects the cell from damage
- participates in metabolism
- many pathogenic bacteria toxic
- participates in the transport of exotoxins
Main component cell wall bacteria is a polysaccharide murein . Depending on the structure of the cell wall, bacteria are divided into two groups: gram-positive (stained by Gram when preparing preparations for microscopy) and gram-negative (not stained by this method) bacteria.
Forms of bacteria: 1 - micrococci; 2 - diplococci and tetracocci; 3 - sarcins; 4 - streptococci; 5 - staphylococci; 6, 7 - rods, or bacilli; 8 - vibrios; 9 - spirilla; 10 - spirochetes
Structure of a bacterial cell: I - capsule; 2 - cell wall; 3 - cytoplasmic membrane;4 - nucleoid; 5 - cytoplasm; 6 - chromatophores; 7 - thylakoids; 8 - mesosoma; 9 - ribosomes; 10 - flagella; II - basal body; 12 - drank; 13 - drops of fat
Cell walls of gram-positive (a) and gram-negative (b) bacteria: 1 - membrane; 2 - mucopeptides (murein); 3 - lipoproteins and proteins
Scheme of the structure of the bacterial cell membrane: 1 - cytoplasmic membrane; 2 - cell wall; 3 - microcapsule; 4 - capsule; 5 - mucous layer
Mandatory cellular structures bacteria - three:
- nucleoid
- ribosomes
- cytoplasmic membrane (CPM)
The organs of movement of bacteria are flagella, of which there can be from 1 to 50 or more. Cocci are characterized by the absence of flagella. Bacteria have the ability to directed forms of movement - taxis.
Taxis are positive if the movement is directed towards the source of the stimulus, and negative when the movement is directed away from it. The following types of taxis can be distinguished.
Chemotaxis- movement based on differences in concentration chemical substances in the environment.
Aerotaxis- on the difference in oxygen concentrations.
When reacting to light and a magnetic field, they arise respectively phototaxis And magnetotaxis.
An important component in the structure of bacteria are derivatives plasma membrane- drank (villi). Pili take part in the fusion of bacteria into large complexes, attachment of bacteria to the substrate, and transport of substances.
Nutrition of bacteria
Based on the type of nutrition, bacteria are divided into two groups: autotrophic and heterotrophic. Autotrophic bacteria synthesize organic substances from inorganic ones. Depending on what energy autotrophs use for synthesis organic matter, there are photo- (green and purple sulfur bacteria) and chemosynthetic bacteria (nitrifying bacteria, iron bacteria, colorless sulfur bacteria, etc.). Heterotrophic bacteria feed on ready-made organic substances of dead remains (saprotrophs) or living plants, animals and humans (symbionts).
Saprotrophs include rotting and fermentation bacteria. The former break down nitrogen-containing compounds, the latter - carbon-containing compounds. In both cases, the energy necessary for their life is released.
Need to mark great value bacteria in the nitrogen cycle. Only bacteria and cyanobacteria are capable of assimilating atmospheric nitrogen. Subsequently, bacteria carry out the reactions of ammonification (decomposition of proteins from dead organic matter to amino acids, which are then deaminated to ammonia and other simple nitrogen-containing compounds), nitrification (ammonia is oxidized into nitrites, and nitrites into nitrates), denitrification (nitrates are reduced into nitrogen gas).
Respiration of bacteria
Based on the type of respiration, bacteria can be divided into several groups:
- obligate aerobes: grow with free access to oxygen
- facultative anaerobes: develop both with access to atmospheric oxygen and in its absence
- obligate anaerobes: develop in the complete absence of oxygen in the environment
Bacteria reproduction
Bacteria reproduce by simple binary cell division. This is preceded by self-duplication (replication) of DNA. Budding occurs as an exception.
In some bacteria, simplified forms of the sexual process have been found. For example, in E. coli, the sexual process resembles conjugation, in which part of the genetic material is transferred from one cell to another upon their direct contact. After this, the cells are separated. The number of individuals as a result of the sexual process remains the same, but an exchange of hereditary material occurs, i.e., genetic recombination occurs.
Sporulation is characteristic only of a small group of bacteria in which two types of spores are known: endogenous, formed inside the cell, and microcysts, formed from the whole cell. When spores (microcysts) form in the bacterial cell, the amount of free water decreases, enzymatic activity, the protoplast is compressed and covered with a very dense shell. Spores provide the ability to transfer unfavourable conditions. They can withstand prolonged drying, heating above 100°C and cooling to almost absolute zero. In their normal state, bacteria are unstable when dried, exposed to direct sun rays, increasing the temperature to 65-80°C, etc. Under favorable conditions, the spores swell and germinate, forming a new vegetative bacterial cell.
Despite the constant death of bacteria (eating them by protozoa, the action of high and low temperatures and other unfavorable factors), these primitive organisms have been preserved since ancient times due to the ability to reproduce quickly (a cell can divide every 20-30 minutes), the formation of spores that are extremely resistant to factors external environment, and their widespread distribution.
Reproduction of bacteria by fission is the most common method of increasing the size of a microbial population. After division, bacteria grow to their original size, which requires certain substances (growth factors).
The methods of reproduction of bacteria are different, but most of their species have a form of asexual reproduction by fission. Bacteria rarely reproduce by budding. Sexual reproduction of bacteria is present in a primitive form.
Rice. 1. The photo shows a bacterial cell at the stage of division.
Genetic apparatus of bacteria
The genetic apparatus of bacteria is represented by a single DNA - chromosome. The DNA is closed in a circle. The chromosome is localized in a nucleotide that does not have a membrane. A bacterial cell contains plasmids.
Nucleoid
A nucleoid is an analogue of a nucleus. It is located in the center of the cell. It contains DNA, the carrier of hereditary information in a folded form. Unwound DNA reaches a length of 1 mm. The nuclear substance of a bacterial cell does not have a membrane, a nucleolus or a set of chromosomes, and does not divide by mitosis. Before dividing, the nucleotide is doubled. During division, the number of nucleotides increases to 4.
Rice. 2. The photo shows a bacterial cell in a section. A nucleotide is visible in the central part.
Plasmids
Plasmids are autonomous molecules folded into a ring of double-stranded DNA. Their mass is significantly less than the mass of a nucleotide. Despite the fact that hereditary information is encoded in the DNA of plasmids, they are not vital and necessary for the bacterial cell.
Rice. 3. The photo shows a bacterial plasmid.
Stages of division
After reaching a certain size characteristic of an adult cell, division mechanisms are launched.
DNA replication
DNA replication precedes cell division. Mesosomes (folds of the cytoplasmic membrane) hold DNA until the division (replication) process is completed.
DNA replication is carried out with the help of enzymes DNA polymerases. During replication, the hydrogen bonds in double-stranded DNA are broken, resulting in two single-stranded daughter DNAs being formed from one DNA. Subsequently, when the daughter DNAs have taken their place in the separated daughter cells, they are restored.
As soon as DNA replication is complete, a constriction appears as a result of synthesis, dividing the cell in half. First, the nucleotide undergoes division, then the cytoplasm. Cell wall synthesis completes division.
Rice. 4. Scheme of bacterial cell division.
Exchange of DNA sections
In Bacillus subtilis, the process of DNA replication ends with the exchange of two DNA sections.
After cell division, a bridge is formed through which the DNA of one cell passes into another. Next, both DNAs are intertwined. Some sections of both DNA stick together. At the sites of adhesion, DNA segments are exchanged. One of the DNA goes along the jumper back into the first cell.
Rice. 5. Variant of DNA exchange in Bacillus subtilis.
Types of bacterial cell divisions
If cell division is ahead of the separation process, then multicellular rods and cocci are formed.
With synchronous cell division, two full-fledged daughter cells are formed.
If the nucleotide divides faster than the cell itself, then multinucleotide bacteria are formed.
Methods for separating bacteria
Division by breaking
Division by breaking is characteristic of anthrax bacilli. As a result of this division, the cells break at the junction points, breaking the cytoplasmic bridges. Then they repel each other, forming chains.
Sliding division
With sliding separation, after division the cell becomes detached and, as it were, slides along the surface of another cell. This method separation is characteristic of some forms of Escherichia.
Split split
With secant division, one of the divided cells with its free end describes an arc of a circle, the center of which is the point of its contact with another cell, forming a Roman quinque or cuneiform (Corynebacterium diphtheria, Listeria).
Rice. 6. The photo shows rod-shaped bacteria forming chains (anthrax bacilli).
Rice. 7. The photo shows a sliding method of separation coli.
Rice. 8. The splitting method of separating corynebacteria.
Type of bacterial clusters after division
Clusters of dividing cells have a variety of shapes, which depend on the direction of the division plane.
Globular bacteria arranged one by one, two by two (diplococci), in packets, in chains, or like bunches of grapes. Rod-shaped bacteria - in chains.
Spiral shaped bacteria- chaotic.
Rice. 9. The photo shows micrococci. They are round, smooth, and white, yellow and red in color. In nature, micrococci are ubiquitous. They live in different cavities human body.
Rice. 10. In the photo there are diplococcus bacteria - Streptococcus pneumoniae.
Rice. 11. The photo shows Sarcina bacteria. Coccoid bacteria cluster together in packets.
Rice. 12. The photo shows streptococcus bacteria (from the Greek “streptos” - chain). Arranged in chains. They are causative agents of a number of diseases.
Rice. 13. In the photo, the bacteria are “golden” staphylococci. Arranged like “bunches of grapes”. The clusters are golden in color. They are causative agents of a number of diseases.
Rice. 14. In the photo, the coiled Leptospira bacteria are the causative agents of many diseases.
Rice. 15. The photo shows rod-shaped bacteria of the genus Vibrio.
Bacterial division rate
The rate of bacterial division is extremely high. On average, one bacterial cell divides every 20 minutes. Within just one day, one cell forms 72 generations of offspring. Mycobacterium tuberculosis divides slowly. The entire division process takes them about 14 hours.
Rice. 16. The photo shows the process of streptococcus cell division.
Sexual reproduction of bacteria
In 1946, scientists discovered sexual reproduction in a primitive form. In this case, gametes (male and female reproductive cells) are not formed, but some cells exchange genetic material ( genetic recombination).
Gene transfer occurs as a result conjugation- unidirectional transfer of part of the genetic information in the form plasmids upon contact of bacterial cells.
Plasmids are small DNA molecules. They are not associated with the chromosome genome and are capable of doubling autonomously. Plasmids contain genes that increase the resistance of bacterial cells to unfavorable environmental conditions. Bacteria often pass these genes on to each other. Transfer of genetic information to bacteria of another species is also noted.
In the absence of a true sexual process, it is conjugation that plays a huge role in the exchange of useful characteristics. This is how the ability of bacteria to exhibit drug resistance is transmitted. The transfer of antibiotic resistance between disease-causing populations is particularly dangerous for humanity.
Rice. 17. The photo shows the moment of conjugation of two E. coli.
Phases of bacterial population development
When inoculated on a nutrient medium, the development of the bacterial population goes through several phases.
Initial phase
The initial phase is the period from the moment of sowing to their growth. On average, the initial phase lasts 1 - 2 hours.
Breeding delay phase
This is the phase of intensive bacterial growth. Its duration is about 2 hours. It depends on the age of the crop, the adaptation period, the quality of the nutrient medium, etc.
Logarithmic phase
During this phase, there is a peak in the rate of reproduction and increase in the bacterial population. Its duration is 5 - 6 hours.
Negative acceleration phase
During this phase, there is a decline in the reproduction rate, the number of dividing bacteria decreases, and the number of dead bacteria increases. The reason for the negative acceleration is the depletion of the nutrient medium. Its duration is about 2 hours.
Stationary maximum phase
During the stationary phase, an equal number of dead and newly formed individuals is noted. Its duration is about 2 hours.
Death Acceleration Phase
During this phase, the number of dead cells progressively increases. Its duration is about 3 hours.
Logarithmic death phase
During this phase, bacterial cells die off constant speed. Its duration is about 5 hours.
Decrease rate phase
During this phase, the remaining living bacterial cells enter a dormant state.
Rice. 18. The figure shows the growth curve of a bacterial population.
Rice. 19. In the photo, a colony of Pseudomonas aeruginosa is blue-green, a colony of micrococci yellow color, Bacterium prodigiosum colonies are blood red in color and Bacteroides niger colonies are black in color.
Rice. 20. The photo shows a colony of bacteria. Each colony is the offspring of a single cell. In a colony, the number of cells is in the millions. The colony grows in 1 - 3 days.
Division of magnetically sensitive bacteria
In the 1970s, bacteria living in the seas were discovered that had a sense of magnetism. Magnetism allows these amazing creatures to navigate along lines magnetic field Earth and find sulfur, oxygen and other substances it needs so much. Their “compass” is represented by magnetosomes, which consist of a magnet. When dividing, magnetically sensitive bacteria divide their compass. In this case, the constriction during division becomes clearly insufficient, so the bacterial cell bends and makes a sharp fracture.
Rice. 21. The photo shows the moment of division of a magnetically sensitive bacterium.
Bacterial growth
When a bacterial cell begins to divide, two DNA molecules separate into different ends cells. Next, the cell is divided into two equal parts, which are separated from each other and increase to their original size. The division speed of many bacteria averages 20 - 30 minutes. Within just one day, one cell forms 72 generations of offspring.
The mass of cells in the process of growth and development quickly absorbs nutrients from environment. This is facilitated by favorable environmental factors - temperature regime, a sufficient amount of nutrients, the required pH of the environment. Aerobic cells require oxygen. It is dangerous for anaerobes. However, unlimited proliferation of bacteria does not occur in nature. Sunlight, dry air, lack of food, heat environmental and other factors have a detrimental effect on the bacterial cell.
Rice. 22. The photo shows the moment of cell division.
Growth factors
For the growth of bacteria, certain substances (growth factors) are necessary, some of which are synthesized by the cell itself, some of which come from the environment. The need for growth factors is different for all bacteria.
The need for growth factors is constant sign, which makes it possible to use it for identifying bacteria, preparing culture media, and using it in biotechnology.
Bacterial growth factors (bacterial vitamins) - chemical elements, most of which are water soluble vitamins group B. This group also includes hemin, choline, purine and pyrimidine bases and other amino acids. In the absence of growth factors, bacteriostasis occurs.
Bacteria use growth factors in minimal quantities and unchanged. A number of chemicals in this group are part of cellular enzymes.
Rice. 23. The photo shows the moment of division of a rod-shaped bacterium.
The most important bacterial growth factors
- Vitamin B1 (thiamine). Takes part in carbohydrate metabolism.
- Vitamin B2" (riboflavin). Takes part in redox reactions.
- Pantothenic acid is a component of coenzyme A.
- Vitamin B6 (pyridoxine). Takes part in amino acid metabolism.
- Vitamins B12(cobalamins are substances containing cobalt). They take an active part in the synthesis of nucleotides.
- Folic acid. Some of its derivatives are part of enzymes that catalyze the synthesis of purine and pyrimidine bases, as well as some amino acids.
- Biotin. Participates in nitrogen metabolism and also catalyzes the synthesis of unsaturated fatty acids.
- Vitamin PP(a nicotinic acid). Participates in redox reactions, the formation of enzymes and the metabolism of lipids and carbohydrates.
- Vitamin H(para-aminobenzoic acid). It is a growth factor for many bacteria, including those inhabiting the human intestines. Folic acid is synthesized from para-aminobenzoic acid.
- Gemin. It is a component of some enzymes that take part in oxidation reactions.
- Kholin. Takes part in the reactions of cell wall lipid synthesis. It is a supplier of methyl group in the synthesis of amino acids.
- Purine and pyrimidine bases(adenine, guanine, xanthine, hypoxanthine, cytosine, thymine and uracil). The substances are needed mainly as components of nucleic acids.
- Amino acids. These substances are components of cell proteins.
Requirement for growth factors of certain bacteria
Auxotrophs To ensure life, they require the supply of chemicals from the outside. For example, clostridia are not able to synthesize lecithin and tyrosine. Staphylococci require the supply of lecithin and arginine. Streptococci require the supply of fatty acids - components of phospholipids. Corynebacteria and Shigella need to be supplied nicotinic acid. Staphylococcus aureus, pneumococci and brucella require vitamin B1. Streptococci and tetanus bacilli - in pantothenic acid.
Prototrophs independently synthesize the necessary substances.
Rice. 24. Different environmental conditions have different effects on the growth of bacterial colonies. On the left is steady growth in the form of a slowly expanding circle. On right - fast growth in the form of "escapes".
Studying the need of bacteria for growth factors allows scientists to obtain a large microbial mass, so necessary in the manufacture of antimicrobial drugs, serums and vaccines.
Read more about bacteria in the articles:
Bacterial proliferation is a mechanism for increasing the number of microbial populations. Bacterial division is the main method of reproduction. After dividing, the bacteria must reach adult size. Bacteria grow by quickly absorbing nutrients from their environment. Growth requires certain substances (growth factors), some of which are synthesized by the bacterial cell itself, and some of which come from the environment.
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 sore throat or gums, despite the fact that only small part bacteria causes 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 mouth. 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 volcanic vents, deep in the oceans where sunlight does not penetrate. Even in the coldest regions (Antarctica) and on the highest mountain peaks, bacteria live.
IN different places Various numbers of bacteria are found. 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, rods 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 ( 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, from one mother cell two daughter cells are formed, similar to the mother one. Under 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 certain types have characteristic outlines and coloring (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).
The kingdom "Bacteria" consists of bacteria and blue-green algae, general characteristics which lies in the small size and absence of a nucleus separated by a membrane from the cytoplasm.
Who are bacteria
Translated from Greek “bakterion” means stick. For the most part, microbes are invisible to the naked eye single-celled organisms, reproducing by division.
Who discovered them
For the first time see the smallest single-celled organisms in homemade microscope An explorer from Holland who lived in the 17th century, Anthony Van Leeuwenhoek, was able to do this. Study the world through the magnifying glass of a magnifying glass he began while working in a haberdashery store.
Anthony Van Leeuwenhoek (1632 - 1723)
Leeuwenhoek subsequently focused on making lenses capable of magnification up to 300 times. In them he examined the smallest microorganisms, describing the information received and transferring what he saw to paper.
In 1676, Leeuwenhoek discovered and presented information about microscopic creatures, to which he gave the name “animalcules.”
What do they eat?
The smallest microorganisms existed on Earth long before the appearance of humans. They have a ubiquitous distribution, feeding on organic food and inorganic substances.
Based on the methods of assimilation of nutrients, bacteria are usually divided into autotrophic and heterotrophic. For existence and development, heterotrophs use waste products from the organic decomposition of living organisms.
Representatives of bacteria
Biologists have identified about 2,500 groups of different bacteria.
According to their form they are divided into:
- cocci having spherical outlines;
- bacilli - rod-shaped;
- vibrios that have curves;
- spirilla – spiral shape;
- streptococci, consisting of chains;
- staphylococci that form grape-like clusters.
According to the degree of influence on the human body, prokaryotes can be divided into:
- useful;
- harmful.
Microbes dangerous to humans include staphylococci and streptococci, which cause purulent diseases.
The bacteria bifido and acidophilus are considered beneficial, stimulating the immune system and protecting gastrointestinal tract.
How do real bacteria reproduce?
Reproduction of all types of prokaryotes occurs mainly by division, followed by growth to the original size. Having reached a certain size, an adult microorganism splits into two parts.
Less commonly, reproduction of similar unicellular organisms is performed by budding and conjugation. When budding on the mother microorganism, up to four new cells grow, followed by the death of the adult part.
Conjugation is considered the simplest sexual process in unicellular organisms. Most often, bacteria that live in animal organisms reproduce in this way.
Bacteria symbionts
Microorganisms involved in digestion in the human intestine are shining example bacteria symbionts. Symbiosis was first discovered by the Dutch microbiologist Martin Willem Beijerinck. In 1888, he proved the mutually beneficial close coexistence of unicellular and legume plants.
Living in the root system, symbionts, feeding on carbohydrates, supply the plant with atmospheric nitrogen. Thus, legumes increase fertility without depleting the soil.
There are many successful symbiotic examples involving bacteria and:
- person;
- algae;
- arthropods;
- sea animals.
Microscopic single-celled organisms assist the systems of the human body, help purify wastewater, participate in the cycle of elements and work to achieve common goals.
Why are bacteria classified into a special kingdom?
These organisms are characterized by their small size, lack of a formed nucleus, and exceptional structure. Therefore, despite their external similarity, they cannot be classified as eukaryotes, which have a formed cell nucleus limited from the cytoplasm by a membrane.
Thanks to all their features, in the 20th century scientists identified them as a separate kingdom.
The most ancient bacteria
The smallest single-celled organisms are considered the first life to emerge on Earth. Researchers in 2016 discovered buried cyanobacteria in Greenland that were about 3.7 billion years old.
In Canada, traces of microorganisms that lived approximately 4 billion years ago in the ocean have been found.
Functions of bacteria
In biology, between living organisms and their environment, bacteria perform the following functions:
- processing of organic substances into minerals;
- nitrogen fixation.
In human life, single-celled microorganisms play an important role from the first minutes of birth. They provide a balanced intestinal microflora, influence the immune system, and maintain water-salt balance.
Bacterial reserve substance
In prokaryotes, reserve nutrients accumulate in the cytoplasm. They accumulate under favorable conditions and are consumed during periods of fasting.
Bacterial reserve substances include:
- polysaccharides;
- lipids;
- polypeptides;
- polyphosphates;
- sulfur deposits.
The main sign of bacteria
The function of the nucleus in prokaryotes is performed by the nucleoid.
Therefore, the main characteristic of bacteria is the concentration of hereditary material in one chromosome.
Why are representatives of the kingdom of bacteria classified as prokaryotes?
The absence of a formed nucleus was the reason for classifying bacteria as prokaryotic organisms.
How bacteria survive unfavorable conditions
Microscopic prokaryotes are capable of long time endure unfavorable conditions, turning into disputes. There is a loss of water from the cell, a significant decrease in volume and a change in shape.
Spores become insensitive to mechanical, temperature and chemical influences. In this way, the property of viability is preserved and effective resettlement is carried out.
Conclusion
Bacteria are the oldest form of life on Earth, known long before the appearance of humans. They are present everywhere: in the surrounding air, water, in the surface layer earth's crust. Habitats include plants, animals and humans.
Active study of single-celled organisms began in the 19th century and continues to this day. These organisms are the main part Everyday life people and have a direct impact on human existence.
The beneficial bacteria that inhabit the human body are called microbiota. They are quite vast in number - one person has millions of them. Moreover, they all regulate the health and normal functioning of each individual. Scientists say: without beneficial bacteria, or, as they are also called, mutualists, the gastrointestinal tract, skin, and respiratory tract would instantly be attacked by pathogenic microbes and would be destroyed.
What should be the balance of microbiota in the body and how can it be adjusted to avoid the development serious illnesses, AiF.ru asked general director biomedical holding of Sergei Musienko.
Intestinal Workers
One of important departments The location of beneficial bacteria is the intestines. It is not without reason that it is believed that this is where the entire human immune system is founded. And if the bacterial environment is disturbed, then the body’s defenses are significantly reduced.
Beneficial intestinal bacteria create literally unbearable living conditions for pathogenic microbes - an acidic environment. In addition, beneficial microorganisms help digest plant foods, since bacteria feed on plant cells containing cellulose, but intestinal enzymes cannot cope with this alone. Also, intestinal bacteria contribute to the production of vitamins B and K, which ensure metabolism in bones and connective tissues, and also release energy from carbohydrates and promote the synthesis of antibodies and regulation of the nervous system.
Most often, when talking about beneficial intestinal bacteria, they mean the 2 most popular types: bifidobacteria and lactobacilli. At the same time, they cannot be called the main ones, as many people think - their number is only 5-15% of total number. However, they are very important, since their positive effect on other bacteria has been proven, when such bacteria can be important factors well-being of an entire community: if they are fed or introduced into the body with the help fermented milk products- kefir or yoghurt, they help other important bacteria survive and reproduce. For example, it is very important to restore their population during dysbacteriosis or after a course of antibiotics. Otherwise, it will be problematic to increase the body’s defenses.
Biological shield
The bacteria that inhabit the skin and respiratory tract of humans, in fact, stand guard and reliably protect their area of responsibility from the penetration of pathogenic organisms. The main ones are micrococci, streptococci and staphylococci.
The skin microbiome has undergone changes over the past hundreds of years, as humans have moved from a natural life in contact with nature to regular washing. by special means. It is believed that human skin is now inhabited by completely different bacteria that lived before. The body with immune system can distinguish dangerous from non-hazardous. But, on the other hand, any streptococcus can become pathogenic for a person, for example, if it gets into a cut or any other open wound on the skin. Excess of bacteria or their pathological activity on the skin and in respiratory tract can lead to development various diseases, and to the appearance unpleasant odor. Today there are developments based on bacteria that oxidize ammonium. Their use makes it possible to seed the skin microbiome with completely new organisms, as a result of which not only the smell disappears (the result of the metabolism of urban flora), but also the structure of the skin changes - pores open, etc.
Saving the microworld
The microcosm of each person changes quite quickly. And this has undoubted advantages, since the number of bacteria can be updated independently.
Different bacteria feed on different substances - the more varied a person’s food is and the more it matches the season, the more choice beneficial microorganisms have. However, if food is heavily loaded with antibiotics or preservatives, bacteria will not survive, because these substances are precisely designed to destroy them. Moreover, it does not matter at all that most of the bacteria are not pathogenic. The result is diversity inner world man is destroyed. And after this they begin various diseases- problems with stool, skin rashes, metabolic disorders, allergic reactions etc.
But the microbiota can be helped. Moreover, it will take only a few days for a slight correction.
Exists a large number of probiotics (with live bacteria) and prebiotics (substances that support bacteria). But the main problem is that they work differently for everyone. Analysis shows that their effectiveness against dysbacteriosis is up to 70-80%, that is, one or another drug may work, or it may not. And here you should carefully monitor the progress of treatment and administration - if the remedies work, you will immediately notice improvements. If the situation remains unchanged, it is worth changing the treatment program.
Alternatively, you can undergo special testing that studies the genomes of bacteria, determines their composition and ratio. This allows you to quickly and competently select the necessary nutrition option and complementary therapy, which will restore the fragile balance. Although a person does not feel slight disturbances in the balance of bacteria, they still affect health - in this case, one can note frequent illnesses, drowsiness, allergic manifestations. Every city resident, to one degree or another, has an imbalance in the body, and if he does not do anything specifically to restore it, then he will probably have health problems from a certain age.
Fasting, fasting, more vegetables, porridge from natural cereals in the morning - these are just a few options eating behavior which is loved beneficial bacteria. But for each person, the diet should be individual in accordance with the state of his body and his lifestyle - only then can he maintain an optimal balance and always feel good.
