an anaerobic spore-forming bacterium.

A group of anaerobic bacteria (bacteria that thrive in the absence of oxygen ). There are 100+ species of Clostridium. They include, for examples, Clostridium difficile , Clostridium perfringens (also called Clostridium welchii), and Clostridium botulinum. See the entire definition of Clostridium

Clostridium is a large genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle.