Isolation, and morphological and chemical properties of an autolysis-deficient mutant of Clostridium botulinum type A.

An autolysis-deficient mutant was isolated from Clostridium botulinum type A 190L by treatment with ethyl methanesulfonate. The cell wall prepared from the mutant autolyzed at much slower rate than that from the parent strain, accompanying with much less liberation of both amino terminals and reducing groups. Electron microscopic observation revealed that the mutant strain was converted to short rod or curved spherical form with thickened cell walls when the growth temperature was shifted from 37 to 45 C. The mutant had a significantly larger amount of non-peptidoglycan-carbohydrate complexes than did the parent strain and became markedly resistant to the autolysin partially purified from the parent, compared with the parent strain. Furthermore, the mutant was fairly tolerant to killing by penicillin. These results suggest that the autolysis deficiency of the mutant was due not only to the deficient production of autolysin but also to the excess accumulation of carbohydrate in the cell wall.