Abstract
The intestinal microbiota is composed of hundreds of species in tens of genera of facultative and anaerobic members of the domains Bacteria and Archaea. Its population exceeds 1×1014 microbial cells. Its mass is one-half that of intestinal content. It influences many physiological and immunological properties of its animal host. This knowledge supports two concepts: 1. the microbiota is an organ of the body essential for survival of man in the natural world, and 2. humans are composites of eukaryotic animal cells and bacterial and archeal members of the biota. These concepts have important implications for research during the 21st Century on human biology and evolution, advancing health, and diagnosis and treatment of disease. Much of that research will be pursued with the technologies of molecular biology and genetics. This review concerns how such technologies might be used to advance our capacities to enhance beneficial influences and minimize harmful effects of the biota.
