High yields of coatless spores of Clostridium perfringens strain 8--6 in a defined medium.

Coatless spores of mutant strain 8--6 of Clostridium perfringens were formed reproducibly at levels exceeding 10(7)/mL in a defined medium. Confirming previous observations, the spores are quite stable in water and resistant to heat, octanol, and ethanol. They also resist 5% phenol. Electron microscopy confirms, with further evidence, the probable absence of any structure exterior to the cortex. The levels of sporulation attained are sufficient to permit recovery and purification for future studies on physicochemical and germination properties. The defined medium makes possible studies on spore coat (and exterotoxin) biosynthesis and coat assembly.