An electron microscope photograph shows the attachment of bacteriophages (T1 coliphages) to the surface of an E. coli bacterium.
At the end of the twentieth century, it became clear that bacteria undoubtedly dominate the Earth's biosphere, accounting for more than 90% of its biomass. Each species has many specialized types of viruses. According to preliminary estimates, the number of species of bacteriophages is about 1015. To understand the scale of this figure, we can say that if every person on Earth discovers one new bacteriophage every day, it will take 30 years to describe all of them. Thus, bacteriophages are the least studied creatures in our biosphere. Most of the bacteriophages known today belong to the order Caudovirales - tailed viruses. Their particles have sizes from 50 to 200 nm. The tail of different lengths and shapes ensures that the virus attaches to the surface of the host bacterium; the head (capsid) serves as a storage for the genome. Genomic DNA encodes structural proteins that form the “body” of the bacteriophage, and proteins that ensure the reproduction of the phage inside the cell during infection. We can say that a bacteriophage is a natural high-tech nanoobject. For example, phage tails are a “molecular syringe” that pierces the wall of a bacterium and, contracting, injects its DNA into the cell.
Bacteriophages use the apparatus of the bacterial cell to reproduce, “reprogramming” it to produce new copies of viruses. The last stage of this process is lysis, the destruction of the bacterium and the release of new bacteriophages.
An electron microscope photograph shows the attachment of bacteriophages (T1 coliphages) to the surface of an E. coli bacterium.
All these molecular subtleties were not known in the second decade of the twentieth century, when “invisible infectious agents that destroy bacteria” were discovered. But even without an electron microscope, with the help of which in the late 1940s it was possible to obtain images of bacteriophages for the first time, it was clear that they were capable of destroying bacteria, including pathogenic ones. This property was immediately in demand by medicine. The first attempts to treat dysentery, wound infections, cholera, typhus and even plague with phages were carried out quite carefully, and the success looked quite convincing. But after the start of mass production and use of phage drugs, euphoria gave way to disappointment. Very little was still known about what bacteriophages are, how to produce, purify and use their dosage forms. Suffice it to say that, according to the results of a test undertaken in the United States at the end of the 1920s, many industrial phage preparations did not contain bacteriophages at all.
The problem with antibiotics
The second half of the twentieth century in medicine can be called the “era of antibiotics.” However, even the discoverer of penicillin, Alexander Fleming, warned in his Nobel lecture that microbial resistance to penicillin occurs quite quickly. For the time being, antibiotic resistance was compensated by the development of new types of antimicrobial drugs. But since the 1990s, it has become clear that humanity is losing the “arms race” against microbes. The uncontrolled use of antibiotics, not only for therapeutic but also for preventive purposes, is primarily to blame, not only in medicine, but also in agriculture, the food industry and everyday life. As a result, resistance to these drugs began to develop not only in pathogenic bacteria, but also in the most common microorganisms living in soil and water, making them “conditional pathogens.” Such bacteria exist comfortably in medical institutions, colonizing plumbing fixtures, furniture, medical equipment, and sometimes even disinfectant solutions. In people with weakened immune systems, who are the majority in hospitals, they cause severe complications.
A bacteriophage is not a living creature, but a molecular nanomechanism created by nature. The bacteriophage tail is a syringe that pierces the wall of the bacterium and injects viral DNA, which is stored in the head (capsid), into the cell.
It's no surprise that the medical community is sounding the alarm. Last year, in 2012, WHO Director General Margaret Chan made a statement predicting the end of the era of antibiotics and the defenselessness of humanity against infectious diseases. However, the practical possibilities of combinatorial chemistry—the basis of pharmacological science—are far from exhausted. Another thing is that the development of antimicrobial agents is a very expensive process that does not bring such profits as many other drugs. So horror stories about “superbugs” are more of a warning, encouraging people to look for alternative solutions.
On medical service
It seems quite logical to see a revival of interest in the use of bacteriophages—the natural enemies of bacteria—to treat infections. Indeed, during the decades of the “antibiotic era,” bacteriophages actively served science, but not medicine, but fundamental molecular biology. It is enough to mention the deciphering of the “triplets” of the genetic code and the process of DNA recombination. Enough is now known about bacteriophages to inform the selection of phages suitable for therapeutic purposes.
Bacteriophages have many advantages as potential drugs. First of all, there are a myriad of them. Although changing the genetic apparatus of a bacteriophage is also much easier than that of a bacterium, and even more so of higher organisms, this is not necessary. You can always find something suitable in nature. We are talking rather about selection, consolidation of sought-after properties and reproduction of the necessary bacteriophages. This can be compared to the breeding of dog breeds - sled dogs, guard dogs, hunting dogs, hounds, fighting dogs, decorative dogs... All of them remain dogs, but are optimized for a certain type of action needed by a person. Secondly, bacteriophages are strictly specific, that is, they destroy only a certain type of microbes without inhibiting the normal human microflora. Thirdly, when a bacteriophage finds a bacterium that it must destroy, it begins to multiply during its life cycle. Thus, the issue of dosage becomes less acute. Fourth, bacteriophages do not cause side effects. All cases of allergic reactions when using therapeutic bacteriophages were caused either by impurities from which the drug was not sufficiently purified, or by toxins released during the massive death of bacteria. The latter phenomenon, the “Herxheimer effect,” is often observed with the use of antibiotics.
Two sides of the coin
Unfortunately, medical bacteriophages also have many disadvantages. The most important problem stems from the advantage of high specificity of phages. Each bacteriophage infects a strictly defined type of bacteria, not even a taxonomic species, but a number of narrower varieties, strains. Relatively speaking, it’s as if a guard dog started barking only at two-meter-tall thugs dressed in black raincoats, and did not react in any way to a teenager in shorts climbing into the house. Therefore, cases of ineffective use are not uncommon for current phage preparations. A drug made against a certain set of strains and perfectly treating streptococcal sore throat in Smolensk may be powerless against all signs of the same sore throat in Kemerovo. The disease is the same, caused by the same microbe, and the strains of streptococcus in different regions are different.
From the author
Since there are countless numbers of bacteriophages in nature and they constantly enter the human body with water, air, and food, the immune system simply ignores them. Moreover, there is a hypothesis about the symbiosis of bacteriophages in the intestine, regulating the intestinal microflora. It is possible to achieve some kind of immune response only with long-term introduction of large doses of phages into the body. But in this way you can achieve allergies to almost any substance. Finally, it is very important that bacteriophages are inexpensive. The development and production of a drug consisting of precisely selected bacteriophages with fully deciphered genomes, cultivated according to modern biotechnological standards on certain strains of bacteria in chemically clean environments and highly purified, is orders of magnitude cheaper than modern complex antibiotics. This makes it possible to quickly adapt phage therapeutic drugs to changing sets of pathogenic bacteria, as well as to use bacteriophages in veterinary medicine, where expensive drugs are not economically justified.
For the most effective use of bacteriophage, accurate diagnosis of the pathogenic microbe, down to the strain, is necessary. The most common diagnostic method now, culture culture, takes a lot of time and does not provide the required accuracy. Fast methods - typing using polymerase chain reaction or mass spectrometry - are being implemented slowly due to the high cost of equipment and higher requirements for the qualifications of laboratory technicians. Ideally, the selection of phage components of a drug could be done against the infection of each individual patient, but this is expensive and unacceptable in practice.
Another important disadvantage of phages is their biological nature. In addition to the fact that bacteriophages require special storage and transportation conditions to maintain infectivity, this method of treatment opens up scope for a lot of speculation on the topic of “foreign DNA in humans.” And although it is known that a bacteriophage, in principle, cannot infect a human cell and introduce its DNA into it, it is not easy to change public opinion. The biological nature and rather large size, compared to low-molecular drugs (the same antibiotics), leads to a third limitation - the problem of delivering the bacteriophage into the body. If a microbial infection develops where the bacteriophage can be applied directly in the form of drops, spray or enema - on the skin, open wounds, burns, mucous membranes of the nasopharynx, ears, eyes, large intestine - then no problems arise.
But if infection occurs in internal organs, the situation is more complicated. Cases of successful treatment of kidney or spleen infections with the usual oral administration of a bacteriophage drug are known. But the mechanism of penetration of relatively large (100 nm) phage particles from the stomach into the bloodstream and internal organs is poorly understood and varies greatly from patient to patient. Bacteriophages are also powerless against those microbes that develop inside cells, for example, the causative agents of tuberculosis and leprosy. A bacteriophage cannot penetrate the wall of a human cell.
It should be noted that the use of bacteriophages and antibiotics for medical purposes should not be opposed. When they act together, a mutual enhancement of the antibacterial effect is observed. This allows, for example, to reduce the dose of antibiotics to values that do not cause significant side effects. Accordingly, the mechanism for bacteria to develop resistance to both components of the combined drug is almost impossible. Expanding the arsenal of antimicrobial drugs gives more degrees of freedom in choosing treatment methods. Thus, the scientifically based development of the concept of using bacteriophages in antimicrobial therapy is a promising direction. Bacteriophages serve not so much as an alternative, but as an addition and enhancement in the fight against infections.
And. O. Head of the Laboratory of Molecular Bioengineering, Institute of Bioorganic Chemistry named after. Shemyakin and Ovchinnikov RAS“Popular Mechanics” No. 10, 2013
At the end of the twentieth century, it became clear that bacteria undoubtedly dominate the Earth's biosphere, accounting for more than 90% of its biomass. Each species has many specialized types of viruses. According to preliminary estimates, the number of bacteriophage species is about 10 15 . To understand the scale of this figure, we can say that if every person on Earth discovers one new bacteriophage every day, it will take 30 years to describe all of them.
Thus, bacteriophages are the least studied creatures in our biosphere. Most of the bacteriophages known today belong to the order Caudovirales - tailed viruses. Their particles have sizes from 50 to 200 nm. The tail of different lengths and shapes ensures that the virus attaches to the surface of the host bacterium; the head (capsid) serves as a storage for the genome. Genomic DNA encodes structural proteins that form the “body” of the bacteriophage, and proteins that ensure the reproduction of the phage inside the cell during infection.
We can say that a bacteriophage is a natural high-tech nanoobject. For example, phage tails are a “molecular syringe” that pierces the wall of a bacterium and, contracting, injects its DNA into the cell. From this moment the infectious cycle begins. Its further stages consist of switching the mechanisms of the life activity of the bacterium to servicing the bacteriophage, propagating its genome, constructing many copies of viral shells, packaging viral DNA in them and, finally, destruction (lysis) of the host cell.
In addition to the constant evolutionary competition between defense mechanisms in bacteria and attack in viruses, the reason for the current balance can be considered the fact that bacteriophages specialized in their infectious action. If there is a large colony of bacteria, where the next generations of phages will find their victims, then the destruction of bacteria by lytic (killing, literally dissolving) phages occurs quickly and continuously.
If there are few potential victims or the external conditions are not very suitable for the effective reproduction of phages, then phages with a lysogenic development cycle gain an advantage. In this case, after penetration into the bacterium, the phage DNA does not immediately trigger the infection mechanism, but for the time being exists inside the cell in a passive state, often introducing itself into the bacterial genome.
In this prophage state, the virus can exist for a long time, going through cell division cycles together with the bacterial chromosome. And only when the bacterium enters an environment favorable for reproduction, the lytic cycle of infection is activated. Moreover, when phage DNA is released from a bacterial chromosome, neighboring sections of the bacterial genome are often captured, and their contents can subsequently be transferred to the next bacterium that the bacteriophage infects. This process (gene transduction) is considered the most important means of transferring information between prokaryotes - organisms without cell nuclei.
All these molecular subtleties were not known in the second decade of the twentieth century, when “invisible infectious agents that destroy bacteria” were discovered. But even without an electron microscope, with the help of which in the late 1940s it was possible to obtain images of bacteriophages for the first time, it was clear that they were capable of destroying bacteria, including pathogenic ones. This property was immediately in demand by medicine.
The first attempts to treat dysentery, wound infections, cholera, typhus and even plague with phages were carried out quite carefully, and the success looked quite convincing. But after the start of mass production and use of phage drugs, euphoria gave way to disappointment. Very little was still known about what bacteriophages are, how to produce, purify and use their dosage forms. Suffice it to say that, according to the results of a test undertaken in the United States at the end of the 1920s, many industrial phage preparations did not contain bacteriophages at all.
The problem with antibiotics
The second half of the twentieth century in medicine can be called the “era of antibiotics.” However, even the discoverer of penicillin, Alexander Fleming, warned in his Nobel lecture that resistance of microbes to penicillin occurs quite quickly. For the time being, antibiotic resistance was compensated by the development of new types of antimicrobial drugs. But since the 1990s, it has become clear that humanity is losing the “arms race” against microbes.
First of all, the uncontrolled use of antibiotics is to blame, not only for therapeutic but also for preventive purposes, not only in medicine, but also in agriculture, the food industry and everyday life. As a result, resistance to these drugs began to develop not only in pathogenic bacteria, but also in the most common microorganisms living in soil and water, making them “conditional pathogens.”
Such bacteria exist comfortably in medical institutions, colonizing plumbing fixtures, furniture, medical equipment, and sometimes even disinfectant solutions. In people with weakened immune systems, who are the majority in hospitals, they cause severe complications.
It's no surprise that the medical community is sounding the alarm. Last year, in 2012, WHO Director General Margaret Chan made a statement predicting the end of the era of antibiotics and the defenselessness of humanity against infectious diseases. However, the practical possibilities of combinatorial chemistry - the basis of pharmacological science - are far from exhausted. Another thing is that the development of antimicrobial agents is a very expensive process that does not bring such profits as many other drugs. So horror stories about “superbugs” are more of a warning, encouraging people to look for alternative solutions.
On medical service
The revival of interest in the use of bacteriophages - natural enemies of bacteria - to treat infections seems quite logical. Indeed, during the decades of the “era of antibiotics,” bacteriophages actively served science, but not medicine, but fundamental molecular biology. It is enough to mention the deciphering of the “triplets” of the genetic code and the process of DNA recombination. Enough is now known about bacteriophages to inform the selection of phages suitable for therapeutic purposes.
Bacteriophages have many advantages as potential drugs. First of all, there are a myriad of them. Although changing the genetic apparatus of a bacteriophage is also much easier than that of a bacterium, and even more so of higher organisms, this is not necessary. You can always find something suitable in nature. We are talking rather about selection, consolidation of sought-after properties and reproduction of the necessary bacteriophages.
This can be compared with the breeding of dog breeds - sled dogs, guard dogs, hunting dogs, hounds, fighting dogs, decorative dogs... All of them remain dogs, but are optimized for a certain type of action needed by a person. Secondly, bacteriophages are strictly specific, that is, they destroy only a certain type of microbes without inhibiting the normal human microflora.
Thirdly, when a bacteriophage finds a bacterium that it must destroy, it begins to multiply during its life cycle. Thus, the issue of dosage becomes less acute. Fourth, bacteriophages do not cause side effects. All cases of allergic reactions when using therapeutic bacteriophages were caused either by impurities from which the drug was not sufficiently purified, or by toxins released during the massive death of bacteria. The latter phenomenon, the “Herxheimer effect,” is often observed with the use of antibiotics.
Two sides of the coin
Unfortunately, medical bacteriophages also have many disadvantages. The most important problem stems from the advantage of high specificity of phages. Each bacteriophage infects a strictly defined type of bacteria, not even a taxonomic species, but a number of narrower varieties, strains. Relatively speaking, it’s as if a guard dog started barking only at two-meter-tall thugs dressed in black raincoats, and did not react in any way to a teenager in shorts climbing into the house.
Therefore, cases of ineffective use are not uncommon for current phage preparations. A drug made against a certain set of strains and perfectly treating streptococcal sore throat in Smolensk may be powerless against all signs of the same sore throat in Kemerovo. The disease is the same, caused by the same microbe, and the strains of streptococcus in different regions are different.
For the most effective use of bacteriophage, accurate diagnosis of the pathogenic microbe, down to the strain, is necessary. The most common diagnostic method now - cultural sowing - takes a lot of time and does not provide the required accuracy. Fast methods - typing using polymerase chain reaction or mass spectrometry - are being implemented slowly due to the high cost of equipment and higher requirements for the qualifications of laboratory technicians. Ideally, the selection of phage components of a drug could be done against the infection of each individual patient, but this is expensive and unacceptable in practice.
Another important disadvantage of phages is their biological nature. In addition to the fact that bacteriophages require special storage and transportation conditions to maintain infectivity, this method of treatment opens up scope for a lot of speculation on the topic of “foreign DNA in humans.” And although it is known that a bacteriophage, in principle, cannot infect a human cell and introduce its DNA into it, it is not easy to change public opinion.
The biological nature and rather large size, compared to low-molecular drugs (the same antibiotics), leads to a third limitation - the problem of delivering the bacteriophage into the body. If a microbial infection develops where the bacteriophage can be applied directly in the form of drops, spray or enema - on the skin, open wounds, burns, mucous membranes of the nasopharynx, ears, eyes, large intestine - then no problems arise.
But if infection occurs in internal organs, the situation is more complicated. Cases of successful treatment of kidney or spleen infections with the usual oral administration of a bacteriophage drug are known. But the mechanism of penetration of relatively large (100 nm) phage particles from the stomach into the bloodstream and internal organs is poorly understood and varies greatly from patient to patient. Bacteriophages are also powerless against those microbes that develop inside cells, for example, the causative agents of tuberculosis and leprosy. A bacteriophage cannot penetrate the wall of a human cell.
It should be noted that the use of bacteriophages and antibiotics for medical purposes should not be opposed. When they act together, a mutual enhancement of the antibacterial effect is observed. This allows, for example, to reduce the dose of antibiotics to values that do not cause significant side effects. Accordingly, the mechanism for bacteria to develop resistance to both components of the combined drug is almost impossible.
Expanding the arsenal of antimicrobial drugs gives more degrees of freedom in choosing treatment methods. Thus, the scientifically based development of the concept of using bacteriophages in antimicrobial therapy is a promising direction. Bacteriophages serve not so much as an alternative, but as an addition and enhancement in the fight against infections.
Final test for the academic year
Option 1
A1. What is the name of the science of the structure of man and his organs?
1) anatomy
2) physiology
3)biology
4)hygiene
A2. What part of the brain is called the small brain?
1) midbrain
2) spinal cord
3) medulla oblongata
4) cerebellum
A3. What muscle group do the temporal muscles belong to?
1) to mimic
2) to chewable
3) to the respiratory
4) to motor
A4. What is the process of destroying microbes by eater cells called?
1) immunity
2) brucellosis
3) phagocytosis
4) immunodeficiency
A5. What is the name of the enzyme in gastric juice that can act only in an acidic environment and breaks down protein into simpler compounds?
1) hemoglobin
2) pituitary gland
3) cerebellum
A6. What are the names of the nerve structures that convert perceived stimuli into nerve impulses?
1) sensory neurons
2) receptors
3) interneurons
4) synapses
B1. Establish the sequence of sections of the human digestive canal.
A) small intestine
B) oral cavity
B) large intestine
D) stomach
E) esophagus
Answer: ________________________
B2. Select the correct answer: What are the characteristics of medicinal serums?
1) 1) used for the prevention of infectious diseases
4) 4)antibodies do not last long in the body
5) 5) used to treat infectious diseases
Q 3. Choose the correct answer: What is the internal environment of the human body formed by?
6) tissue fluid
Q4. Select the correct answer: How does the human skeleton differ from the skeleton of mammals?
1) spine without bends
2) arched foot
C1. What is the function of the respiratory organs?
C2. What is removed from the body through the kidneys?
Final for the academic year
Option 2
A1. What is the name of the warm salty liquid that connects all human organs with each other, providing them with oxygen and nutrition?
1) tissue fluid
4) intercellular substance
A2. Where does the brain begin to divide into right and left halves?
1) at the level of the cerebellum
2) at the level of the medulla oblongata
3) at the level of the midbrain
4) at the level of the spinal cord
A3. What type of tissue is bone tissue?
1) connective tissue
2) epithelial tissue
3) muscle tissue
4) nervous tissue
A4. What makes up the bulk of plasma?
3) red blood cells
4) shaped elements
A5. What is the name of the largest gland in our body, located in the abdominal cavity under the diaphragm?
1) thyroid gland
2) spleen
3) pancreas
A6. What is the means of contact between neurons and cells of working organs?
1) using synapses
2) with the help of alveoli
3) using the vagus nerve
4) using receptors
B1. What are the characteristics of medicinal serums?
1) used for the prevention of infectious diseases
4) antibodies do not last long in the body
5)used to treat infectious diseases
6) after administration they cause mild illness
B2 Establish the sequence of sections of the human digestive canal.
A) small intestine
B) oral cavity
B) large intestine
D) stomach
E) esophagus
Answer: |________________________
2. VZ. How does the human skeleton differ from the skeleton of mammals?
1) spine without bends
2) arched foot
3) the spine is S-shaped curved
4) the facial part of the skull prevails over the brain
5) the chest is compressed in the dorso-abdominal direction
6) the ore cell is compressed from the sides
Q4. How is the internal environment of the human body formed?
2) organs of the chest and abdominal cavities
3) the contents of the stomach and intestines
4) cytoplasm, nucleus and organelles
6) tissue fluid
C1. Name the main criterion that allows us to classify a person as a mammal.
C2. How is the brain connected to the spinal cord?
Before we begin discussing methods of combating microorganisms, I would like to note that many of them are very useful for the human body. The destruction of bacteria that normally live in the large intestine usually leads to the rapid proliferation of various pathogens. Therefore, differential methods are becoming increasingly popular, allowing targeted destruction of harmful bacteria without affecting or timely restoring the normal microflora to which a person owes his health.
Methods for controlling bacterial populations are divided into chemical, biological and physical, as well as aseptic and antiseptic methods. Asepsis is the complete destruction of bacteria and viruses, antiseptics are measures aimed at reducing the growth activity of harmful microorganisms as much as possible. Physical methods include the following:
- Steaming and autoclaving. Allows you to significantly reduce the number of bacteria in food. This method is also successfully used in crop production, making it possible to reduce the content of unwanted microorganisms in the soil. Surviving bacteria and viruses may be present as spores.
- Pasteurization is prolonged heating at temperatures below the boiling point of water. Allows you to preserve some vitamins and organic compounds and the taste of food products. Invented by Louis Pasteur and named after him.
- Treatment with ultraviolet radiation. It involves the use of a special lamp that emits light in the short-wave (ultraviolet) range. It allows you not only to get rid of bacteria living on surfaces, but also from harmful microorganisms in the air. Recently, lamps have been created that can operate indoors without causing harm to humans, plants and animals in them.
- Exposure to high temperatures. Allows you to effectively get rid of heat-sensitive microbes, as well as destroy bacterial spores.
- Exposure to low temperatures. Effective against thermophilic bacteria and viruses. Preference is given to quick freezing methods, the use of which does not give microbes time to form spores. Rapid freezing is also used to study the native (living) structure of fungi, bacteria and viruses.
Chemical destruction of bacteria is also divided into asepsis and antiseptics. The range of substances used is very wide and is annually replenished with new, increasingly safe means for people and animals. Their creation is based on knowledge about the structure of bacteria and viruses and their interaction with various chemicals. Methods for distributing chemical disinfectants are also constantly improving. So, it can be used:
- soaking (sanitation),
- fogging (a great way to destroy germs in the air),
- washing dishes and surfaces,
- combination with physical methods of combating bacteria, fungi, viruses and spores (using hot solutions, boiling, turning on a bactericidal lamp, etc.).
Operating rooms and laboratories. Asepsis
In this case, the most stringent methods are used to get rid of almost all bacteria in the room. Treatment of premises with disinfectants is combined with the use of quartz treatment. Lamps with hard ultraviolet radiation are turned on in the room, which is harmful to all living cells, including those in the air.
Considering the aggressiveness and toxicity of the methods used for humans, the treatment is carried out using special clothing, and turning on the lamps assumes the absence of people and animals in the room.
Selective destruction of microorganisms. Food industry
The production of many healthy food products is impossible without microorganisms. Cultures of beneficial microbes maintained for the production of fermented milk products, hard cheeses, kvass, beer, wine, baking, tea and coffee fermentation and other purposes tend to become contaminated with third-party microflora. This leads to disruption of production technology and a decrease in the quality of food products. To combat polluting microflora, special media are used, control of the composition of which is the key to the purity of the crops grown. At the same time, dishes and equipment in the intervals between technological cycles are subjected to the same treatment as laboratories and operating rooms (disinfectants and quartz lamps). Control of the content of microbes and spores on surfaces and in the air of work areas can be carried out using inoculation on nutrient media.
Destruction of microorganisms with drugs. Infections and dysbiosis
The advent of antibiotics allowed doctors to make a significant breakthrough in the treatment of severe infectious diseases of humans and animals. However, it soon became clear that the destruction of antibiotic-sensitive bacteria in the human large intestine is fraught with the occurrence of digestive disorders and its symptoms may be similar to intestinal infections. Moreover, some conditions that were not treatable with antibiotics were easily cured by using bacterial cultures living in the human large intestine. 
On the other hand, the discovery of bacteria in the stomach responsible for the development of gastritis destroyed the myth that bacterial microflora cannot exist in the acidic environment of gastric juice. The study of the mechanisms that protect these pathogens from destruction and digestion in the stomach has opened a new page in the study of microbes. The advent of tests for the sensitivity of pathogenic microflora to antibiotics has made it possible to select those that are most effective and cause minimal damage to the beneficial inhabitants of the large intestine. Preparations consisting of spores of beneficial microbes and live fermented milk products that restore the microflora of the large intestine have become the final stage in the treatment of all infections. A separate area is the development of synthetic materials for capsules that can withstand high acidity in the stomach and dissolve in the alkaline environment of the intestine.
In the crosshairs of viruses
The task of preserving the microflora of the large intestine is perfectly accomplished by treating bacterial infections with the help of bacteriophages. These are viruses that are very specific in their structure and have a high degree of selectivity in destroying target bacteria. Phage preparations are especially effective for children during the neonatal period, when antibiotics can cause more harm than good, destroying the young and not yet formed microflora of the baby’s large intestine.
What about our body?
Studying the ways in which the human body protects itself from infections is very useful for understanding the processes of interaction between the bacterial ecosystem of the large intestine and the immune system. As is known, microorganisms and their spores living in the large intestine are able to protect themselves from destruction by neutrophils, since there are no receptors on the surface of these cells to which they respond. 
Having the ability for chemotaxis (directed movement towards certain chemicals) and phagocytosis, neutrophils carry out the body’s main defense against bacteria and their spores, making their way through the walls of blood vessels into the site of inflammation. The details of the relationship between the immune system and the inhabitants of the large intestine are still being studied. It is known that healthy microflora in the colon improves the body's immunity, and also competitively displaces pathogenic invaders and their spores, keeping their numbers under strict control.
Organic waste recycling and farming
Microbes living in the large intestine work quite effectively outside it, being forced out of composts as their nutritional base disappears. A certain amount of them is preserved in the form of spores that can survive unfavorable conditions and form a new generation of bacteria when the composition of the nutrient medium changes. All of the above methods are used to obtain pure cultures of microorganisms and spores that can improve soil fertility, both free-living and symbionts. Control of organic and fecal contamination of soils is most often carried out by the presence of Proteus in them, which readily settle in the large intestine and are considered its conditionally pathogenic microflora.
I work as a veterinary medicine doctor. I am interested in ballroom dancing, sports and yoga. I prioritize personal development and mastering spiritual practices. Favorite topics: veterinary medicine, biology, construction, repairs, travel. Taboos: law, politics, IT technologies and computer games.