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Extracellular proteases modify cell wall turnover in Bacillus subtilis.

L K Jolliffe, R J Doyle, U N Streips

    Journal of Bacteriology
    |March 1, 1980
    PubMed
    Summary

    This study investigated how extracellular proteases influence peptidoglycan turnover in Bacillus subtilis. Researchers found that protease-deficient strains had higher turnover rates than wild-type strains, while hyperprotease-producing strains had lower rates. Adding a protease inhibitor increased turnover in hyperprotease strains. Filament formation and incomplete septa were observed in high-protease conditions. Autolysin levels in mutants were not reduced compared to wild-type. These findings suggest proteases may regulate peptidoglycan turnover in B. subtilis. The study contributes to understanding bacterial cell wall dynamics and the role of proteases in this process.

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    Area of Science:

    • Bacterial cell wall biology
    • Microbial protease function

    Background:

    Understanding how bacterial cell walls are maintained is central to microbial physiology. Prior research has shown that peptidoglycan turnover is essential for bacterial growth and division. However, the role of extracellular enzymes in this process remains unclear. Some studies have explored how proteases influence cell wall dynamics, but conflicting results persist. This gap motivated further investigation into protease activity and its impact on cell wall turnover. No prior work had resolved how protease levels correlate with peptidoglycan degradation rates. The relationship between protease production and cell wall stability is still debated. This paper's contribution lies in examining protease effects in Bacillus subtilis. The study addresses a key question in microbial cell wall regulation.

    Purpose Of The Study:

    This study aimed to determine how extracellular proteases influence peptidoglycan turnover in Bacillus subtilis. The specific problem is understanding the regulatory role of proteases in cell wall dynamics. The motivation stems from conflicting reports on protease activity and cell wall stability. Researchers sought to clarify whether proteases modulate peptidoglycan turnover rates. The study focused on comparing wild-type and protease-deficient strains. Growth conditions and protease levels were manipulated to observe effects. The goal was to test if protease activity correlates with cell wall turnover. This work addresses a key gap in bacterial cell wall regulation.

    Keywords:
    Bacillus subtiliscell wall regulationprotease activitypeptidoglycan dynamics

    Frequently Asked Questions

    The study suggests extracellular proteases may regulate peptidoglycan turnover in B. subtilis.

    Adding phenylmethylsulfonyl fluoride increased turnover in hyperprotease-producing strains.

    Filaments and incomplete septa were observed when protease levels were high or subtilisin was present.

    Autolysin levels in mutants were equal to or greater than wild-type, suggesting it is not the main regulator.

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    Main Methods:

    The study used protease-deficient and hyperprotease-producing strains of B. subtilis. Peptidoglycan turnover rates were measured in exponentially growing cultures. Strains were compared under various growth conditions. Protease activity was manipulated using inhibitors like phenylmethylsulfonyl fluoride. Cell wall samples were isolated for analysis. Filament formation and septal integrity were observed microscopically. Autolysin levels were quantified in all mutant strains. The presence of subtilisin in culture media was tested for effects on turnover.

    Main Results:

    Protease-deficient mutants showed higher peptidoglycan turnover than wild-type strain 168. Hyperprotease-producing strains exhibited lower turnover rates. Growth in hyperprotease environments reduced turnover in mutants. Phenylmethylsulfonyl fluoride increased turnover in hyperprotease strains. Isolated cell walls from mutants had autolysin levels equal to or greater than wild-type. Filaments and incomplete septa were observed in hyperprotease strains. Subtilisin presence led to similar filamentous structures in mutants. These findings suggest proteases regulate peptidoglycan turnover.

    Conclusions:

    The study suggests extracellular proteases may regulate peptidoglycan turnover in B. subtilis. Protease-deficient strains showed higher turnover rates, while hyperprotease strains had lower rates. Inhibiting protease activity increased turnover in hyperprotease-producing cultures. Filament formation and incomplete septa were linked to protease presence. Autolysin levels in mutants were not reduced compared to wild-type. These findings align with the hypothesis that proteases influence turnover. The results do not support a role for autolysin levels in regulating turnover. The authors propose protease activity as a regulatory factor in cell wall dynamics.

    Turnover was measured in exponentially growing cultures of B. subtilis strains.

    Protease-deficient mutants showed higher turnover rates than wild-type strain 168.