Lineage: Bacteria[3914]; Bacteroidetes[321]; Bacteroidia[120]; Bacteroidales[120]; Bacteroidaceae[34]; Bacteroides[34]; Bacteroides thetaiotaomicron[1]Bacteroides. This group of microbes constitute the most abundant members of the intestinal microflora of mammals. Typically they are symbionts, but they can become opportunistic pathogens in the peritoneal (intra-abdominal) cavity. Breakdown of complex plant polysaccharides such as cellulose and hemicellulose and host-derived polysaccharides such as mucopolysaccharides is aided by the many enzymes these organisms produce.Bacteroides thetaiotaomicron. Bacteroides thetaiotaomicron is one of the two major Bacteroides species found in the intestine. This organism has been used in studies on gut microflora composition and succession. [Source: NCBI Genome ]