How to Modulate the Gl Microbiome: Effect of Diet, Antibiotics and Probiotics

摘要

The intestinal microbiota is the collection of all live microbes in the Gl tract. It is estimated that the intestine harbours several thousand bacterial phylotypes and a total microbial load between 1012-1014 cells, about 10 times the number of cellscomposing the host body, and 100 times the number of host genes. It is obvious that this tremendous bacterial mass has a crucial impact on host health. The resident microbiota provides nutritional substrates to the host (e.g., short chain fatty acids), stimulates mucosal growth, and protects the host from invasion by pathogens (through competition for oxygen, nutrients and for epithelial adhesion sites). For example, nutrient sources such as complex carbohydrates (e.g., starch, cellulose, pectin) are fermented by bacteria, resulting in the production of short chain fatty acids (SCFA). These act as energy sources for the host, regulate intestinal motility, and are important growth factors for epithelial cells. SCFA also have direct anti-inflammatory properties through expansion of immunoregulatory lymphocytes. Other bacterially-derived metabolites such as indole, a byproduct of tryptophan degradation, and secondary bile acids are also immuno-modulatory, thereby maintaining immune homeostasis and strengthening intestinal barrier function. These beneficial effects of the gut microbiota reach beyond the Gl tract.