Intracellular proteolytic activity during sporulation of Bacillus megaterium.

Intracellular proteolytic activity increased during incubation of the sporogenic strain of Bacillus megaterium KM in a sporulation medium together with excretion of an extracellular metalloprotease. The exocellular protease activity in a constant volume of the medium reached a 100-fold value with respect to the intracellular activity. Maximal values of the activity of both the extracellular and intracellular enzyme were reached after 3-5 h of incubation. After 7 h 20-50% cells formed refractile spores. The intracellular proteolytic system hydrolyzed denatured proteins in vitro at a rate up to 150 mug mg-1 h-1 and native proteins at a rate up to 70 mug mg-1 h-1. Degradation of proteins in vivo proceeded from the beginning of transfer to the sporulation medium at a constant rate of 40 mug mg-1 h-1 and the inactivation of beta-galactosidase at a rate of 70 mug mg-1 h-1. The intracellular proteolytic activity was inhibited to 65-88% by EDTA, to 23-76% by PMSF. Proteolysis of denatured proteins was inhibited both by EDTA and PMSF more pronouncedly than proteolysis of native proteins; 50-65% of the activity were localized in protoplasts. Another strain of Bacillus megaterium (J) characterized by a high (up to 90%) and synchronous sporulation activity was found to behave in a similar way, but the rate of protein turnover in this strain was almost twice as high. The asporogenic strain of Bacillus megaterium KM synthesized the exocellular protease in the sporulation medium, but its protein turnover was found to decrease substantially after 3-4 h. The intracellular proteolytic system of the sporogenic strain J and the asporogenic strain KM were also inhibited by EDTA and PMSF.