B. endodontalis, NA strain of B. melaninogenicus associated with the Papal infections. B. forsythus, N. recently identified anaerobic gram-negative Bacteroides species found in periodontal pockets. B. fragile, n is the most common and dangerous strain of the family of obligate anaerobic bacteria normally found in the mouth, upper respiratory tract, colon and genital organs. B. gingivalis, NA strain of B. melaninogenicus associated with acute periodontitis. B. intermedius, NA strain of B. melaninogenicus associated with acute necrotizing ulcerative gingivitis. B. melaninogenicus, NA small, gram-negative diplobacillus, also known as bacteria melaninogenicum, found in the oral cavity order strattera and pharynx. .