Chemical and ultrastructural studies on the cell wall ofStaphylococcus simulans biovarstaphylolyticus

Cell walls of strains ofStaphylococcus simulans biovarstaphylolyticus andS. aureus FDA 209P were compared ultrastructurally and chemically to investigate the mechanism of resistance of this strain ofS. simulans to its own staphylolytic endopeptidase. Chemical analysis of the peptidoglycans of the various strains examined showed that cells that were more resistant to lysis by the endopeptidase had lower glycine/serine ratios in their cross bridges and that, within a species, the more resistant cells had either fewer residues in these cross bridges or fewer cross bridges. Ultrastructural studies showed that cell wall thickness was not involved in resistance to the enzyme. Comparisons of the endopeptidase susceptibility of intact cells and isolated peptidoglycans from these cells suggested that the three-dimensional structure of the cell wall may play a role in resistance to lysis by the endopeptidase.