Food poisoning bacterium. Coloured scanning electron micrograph of the Gram-positive anaerobic bacteria Clostridium botulinum, responsible for serious food poisoning in humans. C. botulinum grows in badly preserved canned foods, notably meat and fish, and produces the potent exotoxin that causes botulism poisoning. The toxin affects the central nervous system of humans; in fatal cases death results from heart and lung failure due to malfunctions in the cardiac and respiratory centres of the brain. Magnification: x18,000 at 6x4.5cm size.