A group of rod-shaped bacteria commonly found in the soil that grow best under low oxygen conditions. The bacteria formheat-resistant spores which allow them to survive in a dormant state until exposed to conditions that can support theirgrowth. Clostridium botulinum produces botulinum toxin, a highly potent neurotoxin and the basis of the disease botulism.Clostridium botulinum and its spores are widely distributed in nature. They occur in both cultivated and forest soils, bottorrsediments of streams, lakes, and coastal waters, and in the intestinal tracts offish and mammals, and in the gills andviscera of crabs and other shellfish.