Coloured transmission electron micrograph of a group of Fusobacterium nucleatum bacteria. The specimens seen here are negatively stained. They are Gram- negative anaerobic bacilli (rod-shaped) bacteria, typically long & tapered at both ends (fusiform). Fusobacterium nucleatum occurs as the main filamentous bacteria in the dental plaque that forms on the surface of teeth. It ferments carbo- hydrates to lactic acid; plaque is a cause of periodontal disease and tooth decay in humans. Fusobacterium nucleatum is non-motile, and part of the Bacteroides group of bacteria that are obligate animal parasites. Magnification: x3000 at 6x4.5cm size.