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Intracellular proteolytic activity during sporulation of Bacillus megaterium
Abstract:
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.
Insights
Bacillus megaterium sporulation involves increased intracellular proteolytic activity and extracellular metalloprotease excretion. This protein turnover is crucial for spore formation and is inhibited by EDTA and PMSF.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacillus megaterium sporulation is a complex developmental process.
- Proteolytic activity plays a role in cellular regulation and differentiation.
- Understanding protease function is key to deciphering sporulation mechanisms.
Purpose of the Study:
- To investigate the role of intracellular and extracellular proteolytic activity during Bacillus megaterium sporulation.
- To characterize the kinetics and regulation of proteases involved in spore formation.
- To compare protease activity between sporogenic and asporogenic strains.
Main Methods:
- Incubation of Bacillus megaterium strains (KM and J) in sporulation medium.
- Measurement of intracellular and extracellular proteolytic activity over time.
- Enzyme inhibition assays using EDTA and PMSF.
- Analysis of protein turnover and beta-galactosidase inactivation rates.
Main Results:
- Sporogenic strains showed increased intracellular proteolytic activity and extracellular metalloprotease excretion during sporulation.
- Maximal protease activity occurred at 3-5 hours, coinciding with spore formation.
- Proteolytic activity was inhibited by EDTA and PMSF, suggesting metalloprotease and serine protease involvement, respectively.
Conclusions:
- Intracellular and extracellular proteases are integral to Bacillus megaterium sporulation.
- Protein turnover rates differ between sporogenic and asporogenic strains.
- The study highlights the importance of proteolytic systems in bacterial differentiation.