False-colour transmission electron micrograph (TEM) of the bacterium Clostridium tetani, a Gram- positive, spore-forming, anaerobic bacillus (rod- shaped bacterium) that causes tetanus. Members of the Clostridium genus exist as soil saprophytes and as intestinal parasites of animals, giving rise to serious human diseases, including botulism, gas gangrene and severe intestinal infections, in addition to tetanus. Tetanus is common in societies where bare-footed humans live in close association with cattle or domestic animals, although the disease may result from trivial wounds to the skin. Magnification: x7800 at 35mm size, x15600 at 6x7cm size