Repair of salt tolerance and recovery of lost D-alanine and magnesium following sublethal heating of Staphylococcus aureus are independent events

Abstract

Sublethal heating of Staphylococcus aureus S6 in potassium phosphate buffer caused loss of salt tolerance, D-alanine, and magnesium. During incubation in rich complex media all three of the damaged sites were repaired. Repair occurred more slowly but went to completion in a dilute synthetic medium (DSM), free of D-ala. DSM plus penicillin or D-cycloserine allowed repair of salt tolerance but recovery of normal levels of D-ala or Mg was prevented. When DSM-repaired cells were cultured into fresh rich medium they grew rapidly after a short lag. Cells which had acquired their salt tolerance in DSM plus cycloserine and were D-ala and Mg deficient grew slowly and had a lag of 3 h. We suggest that heat damage has two separate primary targets in S. aureus cells: the membrane, which is manifested by loss of salt tolerance, and a second site, possibly teichoic acids, manifested by loss of D-ala and Mg.