Coloured transmission electron micrograph of the bacteria Bacteroides gingivalis (formerly Bacteroides melaninogenicus asaccharolyticus). These Gram-negative, anaerobic bacteria are rod- shaped cocco-bacilli. In this shadow preparation technique, the surface of the bacterial cell wall is seen. B. gingivalis is associated with gingivitis (gum disease) and other periodontal infections including mouth abscesses. It is not confined to the mouth and may infect other regions of the body. In humans it also occurs as normal harmless flora in the mouth, intestine and urogenital tract. Magnification: x7680 at 6x4.5cm size.