Representatives of the microcosm inhabit all surfaces in contact with the environment: skin, mucous membranes of the urinary tract, genital tract, respiratory tract — however, the maximum number of them is found in the large intestine. The composition of the microflora depends on the organ in which it lives. Just as the vegetation and wildlife of a desert or rainforest differs from the flora and fauna of the ocean, so the microbiome of the skin will bear little resemblance to the microbial landscape of the vagina or large intestine. A mutually beneficial alliance with microorganisms has developed in the course of evolution, ensuring human survival among hordes of invisible aggressors. Among the microorganisms inhabiting the human body are bacteria, viruses, fungi, archaea – it is their totality that is called the microbiota or microbiome. Also, the word “microbiome” often refers to the totality of the genetic material of microbes inhabiting a particular ecological niche. The microbiome of the gastrointestinal tract, the microbiome of the nasal cavity, skin, genital, urinary and respiratory tract are isolated in the human body. All microbes that make up the human microbiome can be divided into two groups: symbiont microorganisms that make a huge contribution to maintaining our health, and the so-called opportunistic microbes. The latter begin to multiply when there are insufficient symbiont bacteria and can lead to inflammation. At the same time, the presence of a certain range of opportunistic pathogens is necessary, as they keep the immune system toned. It is possible that further studies of the microbiome will help to understand the hidden role of many microorganisms in the microbiota.

In 2007, the National Institutes of Health of the USA launched a large-scale project “Human Microbiome”, which involved about two hundred scientists from eighty research centers. His tasks include compiling a detailed microbiological “map” of our body, as well as studying the role of evolutionary micro—alliances in maintaining health. At the first stage of the project (from 2007 to 2014), it was possible to establish that the human microecological system includes more than ten thousand varieties of microbes. About 4.5 million genes are involved in the coding of proteins synthesized by microorganisms, while the DNA of human body cells includes, on average, 22 thousand genes. Thus, if we look at the ecosystem of “humans and microbes” from the point of view of the genome, it turns out that 99.5% of the genetic material in this system is the DNA of microorganisms, and only 0.5% is human. Scientists believe that by influencing microbial genes, we can influence many processes, and possibly find the key to the treatment and prevention of various diseases. Studies conducted as part of the second phase of the project (from 2014 to 2017) have shown that there is a close relationship between changes in the microbiome and diseases. Thus, patients with autoimmune intestinal inflammation have been found to have an increased content of E. coli. Women who survived premature birth had fewer lactobacilli and more opportunistic microbes in their vaginal swabs than those who gave birth on time. Thus, a change in the microbiota in the future can be used as a marker to detect the problem in time and prevent its development.

The importance of the microbiota for the body is particularly evident in young children. Passing through the birth canal, contacting the mother and the hospital staff, receiving the first portion of colostrum, the child meets with the first microbes in his life.: they colonize its skin and mucous membranes, exchange genetic information with body cells and form a microbiome. The child’s health depends on which bacteria the body “makes an alliance” with. Thus, colonization of the intestine with symbiont bacteria and the exchange of genetic material with cells of the mucous membrane and the immune system help to form food tolerance — the ability of the immune system to calmly respond to various foods. If, from the first days, foreign microbes predominate in the intestines, rather than symbiont bacteria, immunity often becomes intolerant to many components of food, that is, food allergies. In animals raised in sterile conditions, lymphoid structures responsible for immunity do not form in the intestines, but normally up to 80% of immune cells “live” in the colon. Representatives of the intestinal microbiota “compensate” for many of the disadvantages of our digestion: for example, it is microbial enzymes that help us digest plant fiber. Symbiont bacteria synthesize B vitamins and vitamin K, promote the absorption of nutrients from food, neutralize toxins, displace foreign microbes from the intestine, and produce volatile fatty acids that supply energy to the cells of the mucous membrane. The role of microbiota in the prevention of allergies, cardiovascular diseases, metabolic disorders, mutations leading to cancer, etc. has been proven. Some studies make it possible to trace the relationship between the microbiome and life expectancy. Microbial landscape in the intestines of centenarians (105-109 years old) It is more diverse than the microbiota of middle-aged people: there is an increase in the number of bacteria that promote healthy digestion and strengthen the immune system. At the same time, the total number of microbes in the intestines of people who have overcome the centennial milestone is decreasing.

The nervous and digestive systems are in constant “communication”, using several languages at once: neural, biochemical, immune. In addition, the intestinal microbiome plays an important role in communication between the brain and the digestive tract, whose representatives synthesize a wide range of neuroactive substances: serotonin, gamma-aminobutyric acid, acetylcholine, histamine, dopamine, norepinephrine. The microbiome is also closely related to the hypothalamus—pituitary—adrenal axis, participating in the formation of stress reactions. Mice raised in sterile conditions and deprived of the intestinal microbiome have an overreaction to stress. Scientists suggest that one of the reasons is irritation of nerve cell receptors in the intestinal wall: in antimicrobial mice, their sensitivity is reduced. In turn, prolonged stress leads to adverse changes in the microbiome: the number of protective microorganisms decreases and opportunistic pathogens multiply. It has been established that the gut microbiota affects food preferences and appetite. There is a link between changes in the microbiome and depression: mice react with anxiety and anxiety to the introduction of pathogenic bacteria into the digestive tract, while they do not show any signs of intestinal inflammation. Also, a study conducted in 2014 showed that microbial imbalance is one of the risk factors for developing autism in children.

Millions of microbial genes can work for the benefit of our body, creating the foundation for health and long life, or provoke various disorders and diseases. How to direct this process in the right direction?

• Food. The food substrate for representatives of the intestinal microbiota is fiber. Therefore, for the prosperity of symbiont bacteria, so-called prebiotic foods rich in coarse dietary fiber are necessary: these are vegetables, fruits, unpeeled cereals, and products with bran.
• Probiotics. These are foods and preparations containing strains of symbiont bacteria (as a rule, these are bifidobacteria, lactobacilli, propionic acid bacteria, etc.). The microorganisms in probiotics are not intended for colonization of the intestine, their task is to create conditions for the revival of their own microbiota. The effectiveness of probiotics in the prevention of allergic diseases, especially in children of the first year of life, with diarrhea (intestinal infections, taking antibiotics), in the concomitant treatment of cancer patients, irritable bowel syndrome, in the complex treatment of immunodeficiency, depressive states, etc.
• Microbiota transplantation. Today, the procedure for correcting microbial disorders that have arisen after long-term treatment with antibiotics, chemotherapy, etc., is being introduced by “colonizing” their own beneficial microbes isolated from the patient’s feces before starting treatment. Research shows that this approach makes it possible to deal with intestinal dysfunction and other manifestations of dysbiosis much faster. It was also found that along with the microbiome, some properties of the body can be “transplanted”: when intestinal bacteria were transplanted from obese to thin mice, the latter began to gain weight. Another study showed that the body of elderly mice that eat the feces of their young relatives is significantly rejuvenated.
• Stress relief. Stressful situations, especially long—term ones, gradually lead to the collapse of many body systems, and the microbiome is no exception. This is one of the reasons why constant worries negatively affect the work of the intestines: stool, digestion suffer, and the risk of inflammation increases. In turn, microbial imbalance contributes to excessive stress reactions, forming a vicious circle. Therefore, any methods aimed at relaxation and stress relief: meditation and breathing practices, swimming, yoga, and others — harmonize not only the body and mind, but also the microbiome.