Symbiont bacteria that decompose wood for termites also fix atmospheric nitrogen for them. Symbiotic relationships of microorganisms with plants, animals, humans. Symbiont bacteria are necessary for humans to

1. Cyanobacteria can be part of lichens.

• The bacteria give the fungus some of the glucose produced during photosynthesis.
• The fungus provides water with mineral salts to the bacteria.

2. Nodule bacteria live in special thickenings (nodules) on the roots of plants of the legume family (peas, beans, soybeans).

• Bacteria provide the plant with mineral salts (nitrogen).
• The plant gives bacteria some of the glucose produced by photosynthesis.

3. Bacteria live in the human intestines.

• Bacteria secrete some vitamins and also displace other, more dangerous bacteria from the intestines.
• Man gives bacteria a place to live and food.

Tests

1. Bactria receive glucose
a) from a lichen fungus
b) from legumes
c) from a person

2. Bactria receive mineral salts
a) from a lichen fungus
b) from legumes
c) from a person
d) from lichen fungus and legumes

3. Bacteria
a) they receive glucose in the lichen and release it in the nodules
b) in the lichen they give up glucose, in the nodules they receive
c) they obtain glucose both in the lichen and in the nodules
d) release glucose both in the lichen and in the nodules

4. Bacteria in lichen
a) give glucose to the plant
b) give glucose to the mushroom

5. Bacteria in nodules
a) give glucose to the plant
b) give glucose to the mushroom
c) receive glucose from the plant
d) receive glucose from the fungus

The word “symbiont” comes from the ancient Greek “living together, cohabitation” and refers to various living organisms that support each other’s existence. The process of close and long-term cohabitation of different types of living organisms is called symbiosis. Such relationships between symbionts are successful if they benefit all participants in the process and increase their chances of survival. A striking example is symbiont bacteria living in the human intestine, without which the digestion process, and, consequently, our life would be impossible.

• two animals (a hippopotamus and a bird that brushes his teeth);
• plants and insects (flowers pollinated by only one type of insect);
• microorganisms and plants (nodule bacteria involved in the process of obtaining food from legumes);
• humans and bacteria (microorganisms that live in our intestines help us survive and enjoy life themselves);
• even individual cells with each other (the symbiosis of prenuclear prokaryotic cells gave birth to a full-fledged eukaryotic cell with a clearly defined nucleus, which marked the beginning of the process of evolution on our planet).

And there are also lichens as a result of the symbiosis of a fungus and algae, which survive where neither fungi nor algae can live separately. There is coexistence between the crab and the sea anemone, where the former is a means of transportation and the latter a defensive weapon. And there are countless such examples.

Let's consider two examples of symbiosis of microorganisms with humans and plants - human symbiont bacteria and nodule bacteria involved in the nutrition of legumes.

Macroorganism + microorganism = human

Symbiont bacteria live in our intestines, on mucous membranes, on the skin and constitute the so-called normal microflora. Our native microorganisms:

1. They provide protection to the entire body by killing or depriving “invading” bacteria of food. They do not allow dangerous microbes or viruses coming from outside to settle on the skin or mucous membranes, thereby creating the body’s immune system.
2. Participate in digestion. Bacteria living in the human intestines produce digestive enzymes, without which it is impossible to digest certain types of food.

About 500 species of different bacteria take part in the formation of normal human microflora. Thus, the presence of E. coli in the human body (in certain quantities) is an indispensable condition for the digestion of lactose. In turn, lactobacilli convert the resulting lactose and other carbohydrates into lactic acid, participating in the process of obtaining energy.

Where and how do our little friends live?

Bacteria are found along almost the entire length of the gastrointestinal tract, from the mouth to the rectum. But the most important ones live in the intestines. Here they produce enzymes and vitamins, without which the digestion process is simply impossible.

In each part of the intestine live exactly those microorganisms that are adapted to certain living conditions and nutrient content. For example, in the cecum, the most numerous group is bacteria that break down cellulose, which makes fiber processing possible.

Small intestinal bacteria have to survive in rather harsh conditions. This is where aggressive substances are found that are fatal to many microorganisms. For example, hydrochloric acid, necessary for digestion, kills a significant number of microbes. Only a few species of bacteria and yeast are able to survive in such an environment.

In addition, it is in the small intestine that the process of absorption of nutrients is in full swing. This means that bacteria have to fight for food with the body itself. In addition, incompletely processed substances, which are not always suitable for feeding bacteria, end up here.

The small intestine is connected to the circulatory and lymphatic systems that transport received nutrients. And the nervous system, based on a signal from the small intestine, regulates the composition and amount of hormones needed by the body. That is, the small intestine, thanks to its symbionts, is an energy station and supplier of nutrients.

In the large intestine, bacteria live much more freely, so their number and species diversity are much greater. The body sends undigested food debris and other waste (fragments down to the size of molecules) into the large intestine for further removal.

Enemies of our friends

Antibiotics are a relatively recent invention of mankind. It is difficult to estimate how many lives were saved thanks to this discovery. However, as you know, you have to pay for everything. Antibiotics destroy all bacteria, without distinguishing between good and bad.

That is why, after taking antibiotics, the intestinal microflora looks very sad. This immediately affects not only our digestion, but also greatly reduces our immunity. That is, it turns out that the danger of contracting the next disease becomes greater after taking medications designed to protect our health.

Scientists are trying to break this vicious circle by developing new, highly targeted drugs. But many years of widespread use of antibiotics have led to the fact that the human microflora is becoming increasingly weaker. And the absence or insufficient number of symbiont bacteria entails a whole bunch of chronic diseases: diabetes, cancer, obesity, etc.

Symbionts in the plant kingdom

Plants, in their desire to survive, also do not hesitate to use symbionts. For example, the well-known lichen is not, in fact, a separate plant. It is a symbiotic system of green algae and fungi.

As you know, algae cannot survive without water, and fungi are not able to synthesize nutrients on their own (they use what other microorganisms have produced). But these shortcomings are mutually destroyed in a symbiotic group. Algae, through photosynthesis, create nutrients for fungi, and in return receive a comfortable living environment: the necessary humidity, soil acidity, and protection from ultraviolet radiation. As a result, lichens manage not only to survive, but to feel very confident in rather harsh conditions, where they have no competitors for a place in the sun.

Another example of symbiosis is orchids, in the root system of which fungi and microorganisms live. In this triple alliance, bacteria are responsible for the close relationship between the host plant and the symbiont fungus. The most amazing thing is that not only fungi and microorganisms cannot exist without a plant, but the orchid also dies if its symbionts are destroyed.

But perhaps the most striking example of a plant symbiotic system is nodule bacteria in alliance with plants of the legume family.

How to grow a good crop of legumes

The air we breathe contains nitrogen (as much as 78% of the total volume). This chemical element is necessarily included in the composition of proteins and nucleic acids, which means it is vitally necessary for all living organisms on Earth.

Humans and animals obtain nitrogen through food, mainly from animal and plant proteins. But where do plants get nitrogen from?

Plants cannot obtain nitrogen directly from the atmospheric air on their own. The soil also contains nitrogen, but, firstly, there is very little of it, and secondly, a significant part of it is contained in organic compounds, which plants are not able to absorb.

This is where nitrogen-fixing bacteria come into play. They are able to convert organic compounds containing nitrogen into mineral compounds (nitrates) available for plant nutrition.

A special place among nitrogen-fixing bacteria is occupied by the so-called nodule bacteria. These symbiont microorganisms form nodules on the roots of leguminous plants (clover, lupine, peas, vetch). Nodule bacteria bind free atmospheric nitrogen and deliver it directly to the table of their plant host.

Thus, with the help of symbiont nodules, plants are able to obtain nitrogen, and microorganisms, in turn, take nutrients from plants (products of carbohydrate metabolism and mineral salts) for their own growth and development.

For the successful development of a symbiont system (plant + microorganism), certain conditions are necessary:

• temperature;
• humidity;
• soil reaction;
• strain of bacteria.

Under natural conditions, nodule bacteria of various types are found, and not all of them are quite effective. Therefore, in agriculture, bred strains of microorganisms are used, infecting legume plants with them, which leads to an increase in yield.

However, in the case of legumes, symbiosis is a necessary necessity. If there is enough nitrogen in the soil (for example, nitrogen fertilizers), then nodule bacteria will lose their importance for the host, and their colonies will be destroyed by the plant itself.

So, symbiosis is an important, necessary and sometimes vital thing. Symbiont systems exist in higher animals, plants, fungi, bacteria, algae... In a word, almost everywhere. And we would not have been able to not only survive, but even be born, if nature had not created such a powerful tool for survival as the system of symbionts.

When viruses appear in the body, commensal bacteria send special signals to the immune system that trigger an antiviral immune response.

Previous studies have shown that people lacking these bacteria are susceptible to developing diabetes, obesity, cancer, inflammatory bowel disease and other pathologies.

Date: 06/21/2012

As you know, the human intestine is populated by a wide variety of bacteria that bring invaluable benefits: some of them help digest food, others are an important part of the immune system. In a new study, American scientists discovered another important role of symbiont bacteria - they take part in the destruction of viruses. The study results were published in the journal Immunity.

“In experiments in mice, we found that commensal bacteria send specific signals to the immune system when viruses appear in the body,” explains Dr. David Artis, professor of microbiology at the Perelman School of Medicine, University of Pennsylvania. Pennsylvania). “Under the influence of these signals, the maturation of immune system cells accelerates and their sensitivity to viruses increases. Without these signals, a full-fledged immune response cannot develop.”

Researchers gave laboratory mice a course of antibiotics to reduce the amount of intestinal flora, and then infected them with the influenza virus. Such mice developed an extremely weak immune response to the introduction of the virus, serious damage to the respiratory system was noted, and the disease was often fatal. Next, the scientists analyzed the genes of the immune cells-macrophages of mice that were treated with antibiotics. They noted a noticeable decrease in the activity of genes responsible for antiviral immunity and the production of interferons in macrophages.

Commensal bacteria include not only intestinal flora, but also colonies of symbiotic microorganisms that live on the surface of the skin, in the upper respiratory tract and in the vagina. Previous studies have shown that people suffering from a lack of symbiotic flora are susceptible to developing diabetes mellitus, obesity, cancer, inflammatory bowel diseases and other pathologies.

Source: http://www.ria-ami.ru/news/35070

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Nutrition of bacteria. Autotrophs and heterotrophs.

Respiration of bacteria

Based on the method of obtaining energy, bacteria can be divided into two groups: aerobes and anaerobes. Aerobic bacteria use oxygen to break down organic matter. During splitting, energy is released, which is spent on vital processes. Therefore, aerobic bacteria can only live in an oxygen environment necessary for their respiration.

Anaerobic bacteria obtain energy as a result of the oxygen-free breakdown of organic substances - fermentation or decay.

Anaerobic bacteria were discovered by French biologist Louis Pasteur in 1861. This discovery stunned biologists, since everyone believed that life was necessarily associated with respiration, that is, the use of oxygen. The first anaerobic bacterium discovered by L. Pasteur was Clostridium butyricum, a bacillus that causes fermentation of carbohydrates.

Fermentation is the oxygen-free enzymatic breakdown of carbohydrates.

Lactic acid bacteria, for example, break down a glucose molecule into two lactic acid molecules. They use the energy released in this process for vital processes. This reaction can be written using chemical symbols as follows:

C 6 H 12 0 6 2 C 3 H 6 0 3 + ENERGY

Such reactions occur during souring of milk, making kefir, sauerkraut, soaking apples, and ensiling. Sugars contained in milk, vegetables, and fruits are broken down into lactic acid, and bacteria receive the energy they need. But at the same time, the acidity of the environment gradually increases, and it becomes unsuitable for bacteria to live. Therefore, after fermentation, food products can be stored for a long time.

Anaerobic bacteria are divided into obligate bacteria, which cannot live in the presence of oxygen, and facultative bacteria, which live in both oxygen and oxygen-free environments.

Based on their feeding method, bacteria can be divided into two large groups: autotrophs and heterotrophs.

Autotrophs are bacteria that are capable of synthesizing organic substances from inorganic ones.

If solar energy is used for synthesis, then the bacteria are called photosynthetics, and if the energy released during various chemical reactions is called chemosynthetics.

All autotrophs have two large groups of enzymes. Some provide the synthesis of simple organic substances from inorganic ones, while others, using these substances (glucose, etc.), synthesize complex organic compounds (starch, murein, proteins, etc.).

Photosynthetic bacteria include Purple and Green bacteria. Unlike plants, they obtain hydrogen (H) not from water (H 2 0), but from hydrogen sulfide (H 2 S). Using chemical symbols, the reaction of bacterial photosynthesis can be written as follows:

CO 2 + H 2 S C n H 2 n O n + H 2 0 + S

In this form of photosynthesis, oxygen is not released, and sulfur accumulates in the bacterial cells. This type of photosynthesis is called anaerobic.

Photosynthetic bacteria most often live in bodies of water on the surface of silt, and some species live in hot springs.

The nature of photosynthesis is different (aerobic) in cyanobacteria. These are the oldest organisms that appeared on our planet about 3 billion years ago. They live mainly in fresh water bodies, sometimes causing “water blooms”. Some species live in the seas and oceans, as well as on land, forming green coatings on the soil, stones and tree bark.

Photosynthesis in cyanobacteria is similar to that in plants, and using chemical symbols it can be expressed by the following equation:

CO 2 + H 2 O C n H 2 n O n + O 2

It was cyanobacteria that were the only suppliers of oxygen to the atmosphere for 800 million years.

Chemosynthetic bacteria were first discovered by the Russian scientist S. N. Vinogradsky in 1890. These bacteria use the energy released during the oxidation of ammonia, nitrogen, iron, and sulfur compounds.

Heterotrophic bacteria use ready-made organic substances produced by organisms or the remains of dead bodies for nutrition.

These bacteria have two ways to obtain the necessary energy: fermentation and rotting.

Rotting is the anaerobic enzymatic breakdown of proteins and fats.

If bacteria use the remains of dead bodies for life, they are called saprotrophs. The famous French microbiologist Louis Pasteur pointed out the extremely important role of saprotrophic bacteria in nature at the end of the 19th century. These bacteria, together with mold fungi, are decomposers (from the Latin Reduce - to return). By breaking down organic residues into mineral salts, they cleanse our planet of animal corpses and plant remains, providing living organisms with mineral salts, and closing the cycle of substances in nature.

At the same time, putrefaction bacteria, when they get on food products, cause them to spoil. To protect food products from decomposers, they are subjected to drying, pickling, smoking, salting, freezing, fermentation, or special preservation methods - pasteurization or sterilization.

Louis Pasteur developed a method for preserving liquid foods (milk, wine, beer, etc.), which was called pasteurization. To destroy bacteria, the liquid is heated to a temperature of 65 - 70 ° C and kept for 15 - 30 minutes.

Complete destruction of bacteria is achieved through sterilization. In this case, the products are kept at 140°C for about 3 hours, or they are treated with gases, hard radiation, etc.

Pathogenic bacteria cause diseases such as cholera, plague, tuberculosis, pneumonia, salmonellosis, relapsing fever, tonsillitis, diphtheria, tetanus and many other human diseases, as well as various diseases of animals and plants.

The study of pathogenic bacteria was started by L. Pasteur and was developed in the works of Robert Koch, E. Smith, Danila Samoilovich, Sh. Kitasato.

It has long been known that leguminous plants increase soil fertility. Theophrastus and the Roman scientist Gaius Pliny the Elder wrote about this.

In 1866, the famous Russian botanist and soil scientist M. S. Voronin noticed that the roots of leguminous plants have ha
Characteristic swellings are nodules that are formed as a result of the activity of bacteria.

Only 20 years later, the Dutch microbiologist Martin Beijerinck was able to prove that bacteria settle on the roots of legume plants, receiving ready-made organic substances from them, and in return give the plant much-needed nitrogen, which they absorb from the air.

This is how the symbiosis of bacteria with plants was discovered. Further research showed that not only with plants, but also with animals and even with humans. Several types of bacteria settle in the human intestine and feed on the remains of undigested food, giving in return vitamins and some other substances necessary for human life.

Symbiosis, or mutually beneficial cohabitation of two or more organisms, has been known for a long time. But this does not in any way negate the fact that many of the nuances of this phenomenon have not yet been studied or have been poorly studied.

This amazing natural phenomenon was first discovered by the Swiss scientist Schwendener in 1877. At that time he was just researching lichens. To his deepest amazement, it turned out that these organisms were composite, formed by colonies of fungi and single-celled simple algae. The term “symbiosis” itself appeared in the scientific literature somewhat later. More precisely, it was proposed in 1879 by de Paris.

People figured out the concept itself relatively quickly, but the question of trophism remained. What do some types of symbiotic organisms actually eat? In the case of the same lichens, it was clear that algae live through photosynthesis, but where does the fungal component get its nutrients? If you also don’t know the answer to this question, we suggest reading our article.

General information

Modern scientists have found that symbionts are organisms that feed (most often) on the same thing that the dominant organism consumes. However, this is a very rough and not very correct definition, and therefore several of the most interesting cases should be described in more detail.

You can probably give some examples yourself. Thus, beneficial bacteria for humans are found in large quantities in acidophilic yogurts. People provide these protozoa with an excellent habitat, and bacteria ensure the ideal functioning of our gastrointestinal tract.

By the way, the well-known Kutushov took advantage of this. The symbionts, the cultures of which he sells, provide a significant improvement in the functioning of the gastrointestinal tract even in older people, who often have great problems with this.

Algae as the main symbionts

Biologists have long found out that not a single symbiotic pair of organisms can survive without the participation of algae. Moreover, we are talking not only about aquatic, but also about purely land organisms. They manage to enter into mutually beneficial relationships both with each other and with bacteria and fungi. You should know that the list of algae that are capable of symbiosis is quite limited.

Unusual forms of relationships between algae and other organisms

Lichens and sloths are an example of a long-term stable relationship between two life forms. But symbionts-bacteria and algae do not always form such strong and long-lasting alliances with other organisms. So, they often simply settle on the surface. Of course, in this case there is no talk of a full-fledged symbiosis. This phenomenon is called epiphytosis. A tiny film of simple algae often covers not only the shells of mollusks, but also the surface of the body of some waterfowl and sea animals. Thus, epiphytic algae settle in large quantities even on giant whales.

Scientists still cannot agree on from what point of view the relationship between an epiphyte and a multicellular organism should be viewed. Some believe that this phenomenon is better understood as a primitive, primary version of a symbiotic relationship.

To be fair, it is difficult to agree with this point of view. Epiphytes indeed do not cause direct harm to the organisms on the surface of which they settle, but there is no benefit (visible in any case) from them either.

Damage from epiphytes

But! The phenomenon of epiphytism has been studied very, very poorly. It's possible that this relationship actually benefits not only algae, but also multicellular organisms. The mystery is still waiting for its researcher. What do symbionts eat if they live inside the cell of a higher animal or plant?

Intracellular symbionts

It is not so rare that symbionts can live inside the cells of their “host”. If we talk about the same algae, they are called endophytes. They form endosymbioses, which are much more complex than the phenomena described above. In this case, close, strong and long-term ties are already formed between the partners. Their main difference is that such protozoan symbionts are identified only as a result of fairly detailed and complex cytological studies.

Important! Scientists have proven relatively long ago that the most important cellular organelles - mitochondria in animals and chloroplasts in plants - were formed in ancient times precisely thanks to symbiotic relationships. They were once independent organisms.

At some point, these intracellular symbionts moved to a completely “sedentary” existence inside a living cell, and then became completely dependent on it, transferring control of their genome to its nucleus (partially). So we can safely say that all currently known forms of life that strive for a mutually beneficial existence have every chance of one day becoming one with those organisms with which they have partnerships today.

How do symbionts get inside the cell?

How do microorganisms end up in the cells of higher animals and plants? Some species have mechanisms specially designed for this. Moreover, they are often found not in the symbiont itself, but in the “receiving party.” There is such a small aquatic fern - Azolla. On the lower cavity of its leaves there are narrow passages that lead into cavities that specialize in secreting mucus. It is into these cavities that the blue-green algae Anahaena azollae fall into the caverns along with the flow of water.

The ferns grow, the canals become overgrown, and the algae remain completely isolated. Scientists have long tried to create colonies of other species on the basis of Azolla, but they have not achieved any success. We can say with confidence that the formation of a symbiotic relationship is possible only if a number of parameters completely coincide. In addition, such a union is distinguished by pronounced species specificity.

Thus, symbionts are organisms that feed thanks to processes specific to their species (nitrogen-fixing microorganisms), share valuable substances with a partner, but at the same time require certain conditions that only he can provide.

What are the benefits of such coexistence?

Note that inside the cavities of Azolla there are many nitrogenous compounds. which enter the fern body, not only actively absorb them, but also completely lose the ability to independently fix atmospheric nitrogen. Symbiont organisms reciprocate by supplying the fern with oxygen and some organic substances.

It should be noted that these symbionts do not undergo virtually any changes in their internal organization. However, this is not the case in all cases of intracellular symbiosis. Most often, those algae that enter into mutually beneficial cooperation with other organisms are characterized by a complete reduction of the cell membrane. For example, this happens in blue-green algae, which form a symbiotic relationship with certain species

Termites and intracellular symbionts

For a relatively long time, all scientists were perplexed, reflecting on the digestive processes of termites. How does this species manage to thrive on nothing but wood? Relatively recently, it was found out that the smallest symbionts-bacteria, which are symbionts of protozoa that live in the intestines of termites themselves, are responsible for the direct processing of wood cellulose. This is a complex, but very effective scheme.

But the researchers still didn’t understand where insects get enough energy: after all, cellulose is not particularly nutritious in any case. In addition, they require huge amounts of nitrogen. There is simply no such volume in the digested wood of trees by definition. Recently, scientists from Japan came to a phenomenal result, which they obtained from a careful study of the genome of flagellate symbionts living in the gastrointestinal tract of termites.

What turned out to be in their genome?

There's a lot of interesting stuff there. In particular, scientists were able to detect not only those genes that are responsible for the production of an enzyme for the destruction of cellulose, but also those that are responsible for nitrogen fixation. The latter is a complex process of binding atmospheric nitrogen with the formation of those forms that can be assimilated by plant or animal organisms. This is extremely important, since the nitrogen obtained in this way is used by termites and their flagellates for protein synthesis.

Simply put, in this case, symbionts are organisms that feed on the wood consumed by termites. Symbionts of symbionts of flagellates) are responsible for nitrogen fixation, without which neither the termite itself nor its “guests” can live.

Leguminous plants and symbionts

Since we remembered nitrogen-fixing bacteria, we can’t help but talk about legumes. They, as anyone who has studied botany remembers, are distinguished by an amazingly high content of plant protein. This circumstance has also been extremely surprising to scientists for a long time. The beans managed to produce a sufficient amount of protein even in conditions where there was practically no nitrogen in the soil!

It turned out that its supply was provided by symbiont organisms. Yes, yes, these were the same nitrogen-fixing bacteria that conveniently live in nodules on the roots of all leguminous plants. They extract precious nitrogen from the air, converting it into a highly digestible form.

Commercial use of symbionts

It is not surprising that doctors have been cultivating beneficial bacteria for humans for a long time. At first this happened in the form of the production of yoghurts and other lactic acid products, but today research has reached a completely new level.

Kutushov's symbionts have become especially famous today. What it is? Currently, cultures of fermented milk organisms that improve digestion processes are sold under this brand name.

All Kutushov’s symbionts (more precisely, their cultures) are based exclusively on ancient Mongolian recipes for dishes made from fermented milk products. So they can really improve your overall health and even your appearance.

They were developed by the scientist Kutushov. The symbionts in the cultures are carefully selected; they provide the human body with valuable amino acids and microelements. It is through this that a positive effect is achieved.