Basic physiologic functions of the intestinal bacterial flora

According to the theory of balanced nutrition, the colonization of the bacterial flora of the digestive tract of higher organisms is an undesirable and to some extent harmful side effect. However, the bacterial flora of the gastrointestinal tract is not only not harmful, but is necessary for the normal development of the physiological functions of the macroorganism, and its phylogenetic and ontogenetic development is closely related to the biocenosis of microorganisms.

The microflora of the digestive system also affects its functional characteristics. In particular, bacterial enterotoxins significantly affect intestinal permeability. In most cases, the enzymatic activity of the small intestine in germ-free organisms is higher than in normal ones. However, there is evidence that the level of disaccharidase activity of the small intestine in germ-free and normal rats is the same. The data on pancreatic enzymes are equally contradictory. According to some data, their activity in germ-free animals is higher than in normal ones, while according to others, it is the same. Finally, it should be noted that dysbacteriosis leads to a decrease in the enzymatic activity of the small intestine and, accordingly, to disturbances in membrane digestion.

Intestinal microflora determines the attitude to the immune defense of the organism. Two mechanisms of local immunity are discussed. The first of them is the inhibition of bacterial adhesion to intestinal mucus mediated by local antibodies, including IgA. The second mechanism is the control of the number of a certain bacterial population localized on the surface of the intestinal mucosa due to the presence of antibacterial antibodies in this area. Compared with normal animals, germ-free organisms contain only 10% of cells producing IgA, which participates in local immunity. At the same time, it has been demonstrated that the content of total protein, alpha-, beta- and gamma-globulins in the blood plasma of germ-free animals is lower than in normal animals. In the absence of normal microflora during normal phagocytosis in micromacrophages, hydrolysis of antigens by them slows down.

It should be borne in mind, however, that during anaerobic fermentation formic, succinic and lactic acids and some amount of hydrogen are also formed (usually as individual products). Hydrogen determination is widely used for diagnostics of diseases of the small and especially large intestine.

Thus, the bacterial flora of the gastrointestinal tract is a kind of trophic homeostat, or trophostat, which ensures the destruction of excess food components and the formation of missing products. In addition, some products of its vital activity participate in the regulation of a number of functions of the macroorganism. Therefore, maintaining normal bacterial flora in the body becomes one of the most important tasks in optimizing the nutrition and vital activity of higher organisms, including humans.

The bacterial population of the intestinal mucosa differs significantly from the cavitary population both in composition and in biochemical characteristics. In our laboratory, back in 1975, it was shown that among the bacterial population of the small intestinal mucosa, hemolytic forms are almost absent, which are widely represented in the cavitary population. Already at that time, we suggested that the mucosal population is autochthonous and largely determines the composition of the cavitary population. At the same time, it was found that with a change in diet and diseases, more severe disturbances are observed in the mucosal population, rather than the cavitary population.

I. I. Mechnikov's idea of the advisability of suppressing intestinal bacterial flora should now be subjected to a radical revision. Indeed, as already noted, a comparison of normal and germ-free organisms allowed us to conclude that the latter are metabolically, immunologically, and even neurologically defective and differ sharply from normal ones.

As already noted, the symbiosis of micro- and macroorganisms is probably an ancient evolutionary acquisition and is already observed at the level of primitive multicellular organisms. In any case, in the course of evolution, most multicellular organisms developed symbiosis with bacteria of certain types.

In fact, bacterial flora is a necessary attribute of the existence of complex organisms. The latter, according to modern concepts, should be considered as a single system of a higher hierarchical level than a separate individual. In this case, the macroorganism in relation to microorganisms performs the function of a dominant and regulator of the entire system as a whole. Between it and the symbionts, there is an exchange of metabolites, which include nutrients, various inorganic components, stimulants, inhibitors, hormones and other physiologically active compounds. Suppression of the intestinal bacterial flora often leads to a shift in the metabolic balance of the body.

Thus, it is now becoming clear that in the metabolic sense the organism is a supra-organismic system consisting of a dominant multicellular organism and a specific bacterial polyculture, and sometimes Protozoa.

Endoecosystems have the ability to self-regulate and are fairly stable. At the same time, they have some critical limits of stability, beyond which their irreparable disruption occurs. Normal endoecology can be disrupted by specific and non-specific effects, which leads to a sharp change in the flow of bacterial metabolites. Violation of the composition of the bacterial population of the intestine has been found, in particular, when changing the composition of the diet, with diseases of the gastrointestinal tract, under the influence of various extreme factors (for example, under stress, including emotional, under special conditions, etc.). Dysbacteriosis occurs for various reasons, in particular due to the use of antibiotics.

Thus, in the digestive tract, various variants and links of those trophic chains that we traditionally attribute only to external macroecosystems were discovered.

Antibiotics are a widely and repeatedly used means of treating people and various farm animals. It should be thought that in this case, even with initially normal microflora, it can be partially or completely destroyed, and then replaced by random, as a result of which various disorders in form and degree can arise. However, such disorders can often begin much earlier due to unfavorable conditions arising as a result of non-optimal flora received at birth. Thus, questions about methods of constructing and restoring optimal microflora, i.e. microecology, and endoecology of the body, already arise today.

It should be noted that, in all likelihood, maternity hospitals in the future will have ideal bacterial polycultures. These should be inoculated into children (possibly through breastfeeding or in some other way). It is possible that these polycultures will be collected from the healthiest mothers. It should also be determined whether the optimal polycultures are identical in different countries or should differ due to the climatic and other characteristics of the lives of different groups of people.

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