False-colour scanning electron micrograph (SEM) of chains of the Gram-positive, anaerobic, spore- forming bacteria Clostridium perfringens (also known as Clostridium welchii or Welch's bacillus). The bacterium causes blood poisoning, types of food poisoning, & gas gangrene in humans. C. perfringens secretes exotoxins; one of these, alpha-toxin (a lecithinase enzyme), has the ability to destroy plasma membranes surrounding cells. This may be a primary cause of tissue damage that occurs in cases of gas gangrene. Food poisoning from C. perfringens results from eating foods where the bacteria have developed & formed exotoxins. Magnification: x4100 at 35mm size.