Bacteroidia
The class Bacteroidia is composed of a single order of environmental bacteria. By far, the Bacteroidales order are the most well-studied of the Bacteroidetes. Some members of the genus Bacteroides are opportunistic pathogens. Before the fourth volume of Bergey's Manual of Systematic Bacteriology came out, it was referred to as class Bacteroidetes.
It includes members which are common in the human gastrointestinal microbiota, including Prevotella and Bacteroides.
