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The genus Clostridium consists of bacteria that are obligate anaerobes, Gram-positive, rod shaped, sporeformers, and catalase negative. This genus is one of the largest prokaryotic genera in the phylum Firmicutes (Clostridia is also a class in the phylum), containing over 300 species. All clostridial species form endospores with a strict fermentative type of metabolism. These anaerobes have two forms of growth stages in their life cycle: the vegetative stage, where they divide and proliferate during favorable conditions, and the sporulation stage, in which the vegetative cells form spores under unfavorable conditions and remain dormant until suitable conditions return. The spores are non-metabolizing and highly resistant to heat, desiccation, radiation, oxidation, and many other microbial control agents. The majority of clostridial species do not grow under aerobic conditions, and the vegetative cells are killed upon exposure to oxygen. These anaerobes are ancient bacteria that colonize and thrive in nearly all of the natural anaerobic habitats where organic compounds are present such as soils, aquatic sediments, and the intestinal tracts of animals. |
