Possible Involvement of β-Lactamase in Sporulation in Bacillus cereus

Nonreverting β-lactamase-negative strains were isolated from the β-lactamase-constitutive strain,Bacillus cereus 569 H. These strains differed from both β-lactamase-inducible and -constitutive strains not only in failure to produce β-lactamase but also in failure to autolyze on aging, delayed sporulation, and failure to release free spores from sporangia when produced. The addition ofB. cereus β-lactamase of 15% purity to a final concentration of 10 IU/ml stimulates sporulation and particularly the release of free spores in culture from sporangia of strain 569 (inducible wild-type), 569/H (constitutive mutant of 569), and HPen− , a nonreverting β-lactamase strain isolated from 569/H in this laboratory. Cultures of HPen− did not release free spores without this treatment. Similar stimulation of sporulation and spore release by β-lactamase fromB. cereus were observed in another β-lactamase-negative strain derived from 569/H as well as in certain sporogeny mutants ofB. subtilis . The β-lactamase preparation used in these experiments was free of peptidases, proteases, and autolysins capable of solubilizing wall from vegetative cells. These results, taken with our previous finding that a soluble peptidoglycan inducer becomes available in cultures ofB. cereus only at sporulation and that normal derepression of β-lactamase accompanies normal sporulation, suggest that β-lactamase inB. cereus may be involved in peptidoglycan metabolism during sporulation and possibly the breakdown of sporangial wall with the concomitant release of mature spores.