Differences in penicillin-binding proteins of Streptococcus pyogenes and two derived, stabilized L forms

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Streptococcus pyogenes can differentiate into stable L-forms, which lack cell walls.
• Penicillin-binding proteins (PBPs) are crucial enzymes involved in bacterial cell wall synthesis.
• Understanding PBP alterations in L-forms is key to comprehending their unique physiology and potential therapeutic implications.

Purpose of the Study:

• To compare the penicillin-binding proteins (PBPs) of Streptococcus pyogenes coccal form with its osmotically fragile and physiologic isotonic L-forms.
• To investigate quantitative and qualitative differences in PBPs between the coccal and L-form states.
• To correlate observed PBP changes with cell wall synthesis and membrane alterations.

Main Methods:

• Comparative analysis of PBPs using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
• Quantification of PBP numbers and relative amounts in membrane preparations.
• Assessment of PBP deacylation (half-life) rates.
• Analysis of PBP secretion by intact cells.

Main Results:

• The number of PBPs decreased from 6 in cocci to 4 (osmotically fragile L-form) and 2 (physiologic isotonic L-form).
• Relative PBP amounts were significantly altered, with the largest PBPs (1 and 2) absent in L-forms.
• PBPs in the osmotically fragile L-form showed slower deacylation, unlike those in the stable physiologic isotonic L-form.

Conclusions:

• Streptococcus pyogenes L-forms exhibit distinct PBP profiles compared to the parent coccus, with significant quantitative and qualitative differences.
• Altered PBP composition and kinetics in L-forms likely contribute to modified cell wall synthesis and membrane characteristics.
• These findings provide insights into the adaptation and stability mechanisms of bacterial L-forms.