Clostridium tetani. Coloured Scanning Electron Micrograph (SEM) of a cluster of the bacteria Clostridium tetani, cause of tetanus (lockjaw). These bacteria are Gram-positive, spore-forming, rod-shaped anaerobic bacilli. Clostridium tetani produce spores which live in soil and in manure, but are also found in the human intestine. If the spores or bacteria enter the body through a wound, tetanus may result. Bacteria multiply producing a nerve toxin which affects the activity of muscles. Stiffness of the jaw (lockjaw), back and facial muscles may occur with painful spasms. DPT vacci- nation in childhood immunizes against tetanus. Magnification: x5000 at 5x7cm size.