Table 1.

Functions of commensal bacteria in the gut

Protective functions Pathogen displacement Competition for nutrients Competition for receptors Production of anti-microbial factors

Metabolic functions Fermentation of non-digestible dietary substances Generation of short chain fatty acids Salvage of energy source Synthesis of essential vitamins (vitamin K and B12, niacin, biotin and folate)

Structural functions Regulation of epithelial cell turnover Promotion of epithelial cell differentiation Fortification of epithelial barrier Stabilization of tight junctions

Immune functions Induction of secretory IgA Induction of oral tolerance Shaping of immune microenvironment