Clostridium tetani is an obligate anaerobic, Gram-positive, spore-forming bacillus.

The material describes *C. tetani* as Gram-positive, spore-forming, and obligately anaerobic. These features help explain why its spores may persist in the environment while germination occurs in an anaerobic wound environment. **Key takeaway:** The organism's spore-forming and anaerobic properties are central to its epidemiology and pathogenesis.\n\n**Glossary:** **Obligate anaerobe**: an organism that grows in the absence of oxygen; **bacillus**: a rod-shaped bacterium.