Complementation characteristics of newly isolated mutants from two groups of strains of Clostridium perfringens.

1. Mutants of a group were converted to b group by a second NG treatment. The resulting b group mutants could not produce the marker products that had been lost on the first NG treatment but could produce the others by complementation. 2. Mutants of b group were converted to constitutive mutants by a second NG treatment. No back mutation from b group was observed.