Mitsuokella dentalis. Coloured transmission electron micrograph (TEM) of bacteria that cause tooth decay, Mitsuokella dentalis. These cells were isolated from dental root canals. They are gram negative rod-shaped bacteria. The surface of each cell is covered with numerous short & thick protuberances. These are called pili, some of which play a role in bacterial reproduction. Around the cells are dots and trails of a lipo- polysaccaride from the cell walls of the bacteria. These bacteria are anaerobic (do not require oxygen to live) and are related to the genus Bacteroides. Magnification: x7000 at 6x7cm size. Magnification; x24,000 at 8x10 nich size.