Clostridium perfringens bacterium, coloured TEM. This bacterium, also called Clostridium welchii or Welch's bacillus, is an individual Gram-positive, anaerobic, spore-forming bacterium that causes blood poisoning, types of food poisoning and gas gangrene. C. perfringens secretes exotoxins; one of which, alpha-toxin (a lecithinase enzyme) has the ability to destroy plasma membranes surrounding cells, a possible cause of tissue damage in gas gangrene. Food poisoning from C. perfringens results from eating foods where the species has developed & formed exotoxins. Magnification: x43,000 when printed 10 centimetres wide.