Timing of enzyme synthesis during outgrowth of spores of Bacillus cereus. I. Ordered enzyme synthesis.

During outgrowth of spores of Bacillus cereus T, the pattern of enzymes synthesized varied with respect to time. The periods of synthesis of alpha-glucosidase, l-alanine dehydrogenase, and histidase were ordered; each began at a specific time and synthesis continued for only a brief period. An examination of the timing of induced alpha-glucosidase and induced histidase was made to determine whether specific regions of the genome were continually available for transcription and regulation during this period. Several observations indicated that inducers could function during outgrowth, but for only a limited time interval. The period of induced enzyme synthesis occurred over the same interval as that observed for uninduced and catabolically repressed cultures. When inducer was added partway through the period of gene expression, the level of enzyme induction was diminished. Addition of inducer at a time after the period of gene expression had no significant effect. Since messenger ribonucleic acid formed during outgrowth had a half-life of only a few minutes, it was concluded that ordered enzyme synthesis was a result of ordered transcription of the corresponding portion of the genome. An examination of the timing of induced alpha-glucosidase and histidase synthesized in the presence of actinomycin D supported this conclusion.