Bacteroides species are normally mutualistic, making up the most substantial portion of the mammalian gastrointestinal microbiota,[4] where they play a fundamental role in processing of complex molecules to simpler ones in the host intestine.[5][6][7] As many as 1010–1011 cells per gram of human feces have been reported.[8] They can use simple sugars when available; however, the main sources of energy for Bacteroides species in the gut are complex host-derived and plant glycans.[9] Studies indicate that long-term diet is strongly associated with the gut microbiome composition—those who eat plenty of protein and animal fats have predominantly Bacteroides bacteria, while for those who consume more carbohydrates the Prevotella species dominate.[10]
^Finegold SM, Sutter VL, Mathisen GE (1983). Normal indigenous intestinal flora (pp. 3-31) in Human intestinal microflora in health and disease. Academic Press. ISBN978-0-12-341280-5.
^Appleman MD, Heseltine PN, Cherubin CE (Jan 1990). "Epidemiology, antimicrobial susceptibility, pathogenicity, and significance of Bacteroides fragilis group organisms isolated at Los Angeles County-University of Southern California Medical Center". Reviews of Infectious Diseases. 13 (1): 12–18. doi:10.1093/clinids/13.1.12. PMID2017610.