Research The gut of vertebrates is home to a bacterial collection of amazing biodiversity. For example, several hundred bacterial species live together in the human colon where they form a self-regulating community. The community is often referred to as the ‘microbiota’. Obligately anaerobic bacteria predominate in the colonic microbiota. They hydrolyze plant residues from the diet that have not been digested in the small intestine. So, the gut microbiota begins the recycling of dietary waste inside the colon by degrading plant polymers and fermenting the hydrolysis products to short chain fatty acids. These fatty acids provide a source of calories for the human because they are taken up by the intestinal mucosa and incorporated into biochemical pathways. Members of the microbiota also recycle human secretions, such as mucus. Our research objectives are to understand how the members of the microbiota (referred to as commensals) live in the gut, and the consequences to the host of this life-long association with these bacteria.