Part played by the intestinal microflora in maintenance of the normal intestinal biocenosis
The normal intestinal microflora is necessary for maintaining at the optimal level the metabolic processes proceeding in the macroorganism and for provision of the high colonization resistance of the host organism in relation to the pathogenic microbes. The ecological system, which components include the macroorganism, its microflora and environment, is characterized by integration and capability of self-regulation. Various unfavorable impacts and pathological conditions may cause the qualitative and quantitative changes in the normal intestinal microflora.
The normal intestinal autoflora takes an active part in the digestion processes. Proteins, fats, carbohydrates non-split in the little intestine are subjected to enzymatic cleavage under the action of large intestine microflora. The formed bacterial digestion products are readily absorbed by the intestinal wall and represent the full-value plastic and energy material for the body metabolic processes. The normal intestinal autoflora of newborns and infants facilitates casein hydrolysis by phosphoprotein-phosphatase synthesizing and promotes the lactobiose disposal by cleavage with β-galactosidase. The end products of protein and amino acid cleavage formed as a result of bacterial hydrolysis – indole, skatole and phenol activate the intestinal peristalsis and stimulate the normal transit of fecal matter in the intestines.
The normal intestinal autoflora participates in biochemical processes of the fat and pigment metabolism. Under the action of normal microflora of large intestine the direct bilirubin (bilirubin diglucuronide) transforms into urobilinogen. With the quantitative or qualitative changes of the intestinal microbial landscape the direct bilirubin excreted with bile is subjected to enzymatic action of beta-glucuronidase of the intestinal wall with the toxic unconjugated (indirect) bilirubin forming. The latter, when absorbed by the intestines, enters the blood flow and may raise the intoxication potential of jaundice, particularly in case of newborns with their venous duct (ductus venosus Arantii) still functioning. The natural intestinal autoflora participates in the choline, bile and aliphatic acid metabolism with formation of deoxycholic acid, coprostanol and other metabolism products. The formed products of bacterial fermentation promote the fecal mass resetting and intestinal content evacuation. It was noted that the intestinal microflora produces a favorable effect on the processes of absorption and metabolism, disposal of calcium, iron and vitamin D.