Bacteroides melaninogenicus is a species of bacterium in the normal flora of the upper respiratory tract. It is an important human pathogen in various anaerobic infections, often mixed with other aerobic and anaerobic bacteria. B. melaninogenicus is an anaerobic, Gram-negative rod, named for its blackcolonies, and black pigment. The name Bacteroides melaninogenicus was later changed to Prevotella melaninogenica. Steroids may facilitate growth.