Effect of salt concentration in the recovery medium on heat-injured Streptococcus faecalis.

Properties relating to the recovery of three heat-injured strains of Streptococcus faecalis were studied. All strains were cultured in all purpose plus Tween broth (APT) at 30 C for 24 hr before being subjected to heat in fresh APT broth. APT recovery medium containing various added amounts of NaCl, KCl, MgCl(2), or KCl and MgCl(2) was used to assess the effect of salts on the recovery of thermally injured S. faecalis. It was evident that, upon exposure to heat, S. faecalis cells became sensitive to increased salt concentrations. Analyses to determine the ribonucleic acid (RNA) content of heated cells showed a reduction of cellular RNA, but the per cent reduction was not directly proportional to the per cent reduction of the viable cells.