Bacteroidetes is a diverse group of bacteria common in human gut, in marine and freshwater systems. Their levels rise as body weight is decreased. The name of this bacterial phylum changed several times over the past years and is also known as the Cytophaga–Flexibacter–Bacteroides (CFB) group. It includes four classes: Bacteroidia (858 strains), Flavobacteria (3583 strains), Sphingobacteria (787 strains), and Cytophagia (765 strains), and many unclassified strains representing around 7000 different species (NCBI, October 2010). They are non-motile, flagellated, or move by gliding.
Bacteroidetes in the gut are responsible for degradation of high molecular weight organic matter, i.e., proteins and carbohydrates. Their genomes appear to be highly plastic and frequently reorganized through genetic rearrangements, helping them to adaptation to distinct ecological niches.
Bacteroidetes in the gut are responsible for degradation of high molecular weight organic matter, i.e., proteins and carbohydrates. Their genomes appear to be highly plastic and frequently reorganized through genetic rearrangements, helping them to adaptation to distinct ecological niches.
Many Bacteroidetes, especially Bacteroides are opportunistic pathogens. The figure shows predominant sites colonized by Bacteroides and other anaerobic bacilli. Their levels are higher in celiac disease and more severe forms of IBS (Rome III criteria). Prevotella, and Fusobacterium are prevalent in the body and usually don't cause problems, but may become involved in infections throughout the body (see Fig.). Within the Bacteroides group, B fragilis is the most common pathogen, followed B thetaiotaomicron and other members of the B fragilis group. Among the bile-sensitive Prevotella species, the ones most commonly encountered clinically are P melaninogenica, P oris, and P buccae. Porphyromonas species seem to be much less pathogenic except in dental infections. Fusobacterium nucleatum is the Fusobacterium species most often found as a pathogen, but F necrophorum occasionally produces serious disease. Several species of Flavobacteria are known to cause disease in freshwater fish. Bacteria that belong to the genus Sphingobacterium are Gram-negative, non-fermentative bacilli, ubiquitous in nature and rarely involved in human infections but might be pathogenic in Cystic Fibrosis (CF) patients.
