The familyPrevotellacae is composed of four genera.
Prevotella species are among the most numerous microbes culturable from the rumen and hind gut of cattle and sheep, where they help the breakdown of protein and carbohydrate foods. They are also present in humans, where they can be opportunistic pathogens. Prevotella, credited interchangably with Bacteroides melaninogenicus, has been a problem for dentists' patients for years. As a human pathogen known for creating periodontal and tooth problems, Prevotella has long been studied to counteract its pathogenesis.