No abstract

Major quantitative, but not qualitative, differences in the various species of proteins in purified membranes from Streptococcus pyogenes and its stabilized L-form have been demonstrated by acidic and alkaline disc gel electrophoresis with and without urea. The fact that no significant differences in the amino acid content or composition between these two membranes could be demonstrated emphasizes that these results are probably due to changes in the relative amounts of the various species of proteins in this subcellular component. The possibility of these protein changes in the L-form membrane being related to its inability to synthesize a rigid cell wall is discussed. Finally, phage-associated lysin, routinely used for removal of the group A streptococcal cell wall, does not appear to affect the protein profile or amino acid composition of the membrane either metabolically or nonmetabolically.

SUMMARYThe minimal inhibitory concentrations of various antibiotics for a strain of Streptococcus pyogenes and a stable L-form of it were determined. These results were evaluated with those of other investigators similarly performed with S. faecalis and derived protoplasts. Differences in reaction to puromycin, bacitracin and ristocetin were apparent only between the wall-less derivatives. The polyene antibiotics nystatin and filipin and two antimicrobial agents, isatin 3-thiosemicarbazone and 1-methyl-isatin 3-thiosemicarbazone, were ineffective or only slightly inhibitory on growth of S. pyogenes and its L-form. Labelled penicillin studies with this group A streptococcus and its L-form indicated that the binding sites for penicillin were probably distinct from those concerned with streptococcal wall formation.