An effect of thermal injury on Staphylococcus epidermidis : 16S RNA degradation resulting from the loss of cellular magnesium

Abstract

Exposure of Staphylococcus epidermidis to sublethal temperatures produced a temporary change in the salt tolerance of the organism. After sublethal heat treatment at 50 C for 15 min, 96% of the viable population was unable to reproduce on media containing 7.5% NaCl. The data reveals that thermal injury resulted in alterations in the cell membrane, which allowed leakage of 260nm absorbing material into the heating menstruum. Polyacrylamide gel electrophoresis revealed 16S ribosomal RNA to be extensively degraded in thermally injured cells, whereas 23S and 5S RNA were unaffected. When thermally injure cells were incubated in complex media, 16S RNA was regenerated accompanied by a return of salt tolerance in a system where DNA synthesis was lacking. In the presence of high Mg2+ concentrations in the heating media, leakage of RNA was suppressed and the degradation of 16S RNA was not observed. Ribosomal RNA degradation is therefore, an effect of magnesium loss and is not an effect of heat in thermally injured cells of S. epidermidis.