Autolytic activity associated with competent group H streptococci.

Area of Science:

• Microbiology
• Cell Biology
• Molecular Biology

Background:

• Competence in streptococci is a transient physiological state enabling genetic transformation.
• Autolysis, or self-digestion, is a poorly understood phenomenon in bacterial cells.

Purpose of the Study:

• To investigate the relationship between cell competence and autolysis in group H streptococci.
• To characterize the conditions and factors influencing streptococcal autolysis.

Main Methods:

• Comparing autolysis rates of competent versus noncompetent streptococcal cells under various conditions (temperature, buffer, additives).
• Assessing the lytic activity of cell-free supernatants from competent cell lysates.
• Utilizing electron microscopy to observe autolysis sites.
• Manipulating competence factor (CF) levels and activity to assess its impact on autolysis.

Main Results:

• Competent cells of group H streptococci (strains Wicky and Challis) exhibited marked autolysis at 37°C in a specific buffer with 2-mercaptoethanol, unlike noncompetent cells.
• Autolysis was temperature-dependent and inhibited by heat.
• Addition of native deoxyribonucleic acid (DNA) to competent cells slowed autolysis.
• Supernatants from competent cell lysates showed specific lytic activity against noncompetent cells of the same strain, which was heat-inactivated.
• Electron microscopy revealed autolysis occurring at the cell cross-wall formation site.
• Conditions preventing competence also prevented autolysis, suggesting an inductive role for CF.

Conclusions:

• A strong correlation exists between the development of competence and the onset of autolysis in group H streptococci.
• Competence factor (CF) appears to indirectly induce autolysis, potentially through mechanisms involving DNA and cell wall processes.
• The observed autolysis is a specific phenomenon localized to the cross-wall and mediated by factors released from competent cells.