C. botulinum is a large, Gram-positive, anaerobic bacillus that forms spores near the ends of its cells. This bacterium is widely distributed in soil, pond and lake sediments, and decaying vegetation. It is sometimes found in the gastrointestinal tracts of birds, mammals, and fish. C. botulinum is the bacterium responsible for foodborne botulism. There are seven types of botulinum toxin produced by the bacterium, each conferring a different type of immunity. The toxins produced by Clostridium botulinum are designated as A, B, C1, D, E, F, and G. Not all strains of C. botulinum produce toxins, but only toxin types A, B, E, and F are pathogenic to humans.