Inhibition of Colony-spreading Activity of Staphylococcus aureus by Secretion of δ-Hemolysin

Staphylococcus aureus spreads on the surface of soft agar, a phenomenon we termed colony spreading. Here, we found that S. aureus culture supernatant inhibited colony spreading. We purified delta-hemolysin (Hld, delta-toxin), a major protein secreted from S. aureus, as a compound that inhibits colony spreading. The culture supernatants of hld-disrupted mutants had 30-fold lower colony-spreading inhibitory activity than those of the parent strain. Furthermore, hld-disrupted mutants had higher colony-spreading ability than the parent strain. These results suggest that S. aureus negatively regulates colony spreading by secreting delta-hemolysin.