ABSTRACT

The human gastrointestinal tract harbors a complex collection of microorganisms, which

form a specific individual microbiota for each person. This specific microbiota is depen-

dent on the environment and genetic factors. The total number of microbes in the intestinal

tract can be estimated at 1012 bacteria/g of intestinal contents. Several hundred bacterial species can be identified using traditional culture methods. The use of molecular methods

has increased the number of bacteria in the intestinal mucosa and intestinal contents and

also changed our understanding of the composition of the intestinal microbiota. The

microbiota is metabolically active, and its composition is related to many disease states

within and outside the intestine.