IDENTIFICATION AND MOLECULAR CHARACTERIZATION OF A PUTATIVE REGULATORY LOCUS THAT AFFECTS AUTOLYSIS IN STAPHYLOCOCCUS-AUREUS

Previously in our laboratory, a PCR-based strategy was used to isolate potential sensor gene fragments from the Staphylococcus aureus genome . One DNA fragment was isolated that shared strong sequence similarity to genes encoding bacterial sensor proteins, indicating that it origi nated from within a potential staphylococcal sensor protein gene. In t his study, the DNA surrounding the PCR product origin was cloned and s equenced. This analysis revealed the presence of two genes, termed lyt S and lytR, whose deduced amino acid sequences were similar to those o f members of the two-component regulatory system family of proteins. S . aureus cells containing an insertional disruption of lytS exhibited a marked propensity to form aggregates in liquid culture, suggesting t hat alterations in cell surface components exist in this strain. Trans mission electron microscopic examination of these cells revealed that the cell surface was rough and diffuse and that a large proportion of the cell population had lysed. The lytS mutant also exhibited increase d autolysis and an altered level of murein hydrolase activity produced compared with the parental strain, NCTC 8325-4. These data suggest th at the lytS and lytR gene products control the rate of autolysis in S. aureus by affecting the intrinsic murein hydrolase activity associate d with the cell.