Requirements of Salmonella typhimurium for Recovery from Thermal Injury

The heating of Salmonella typhimurium 7136 at 48 C for 30 min produces a population of cells that are incompetent at division on Levine Eosin Methylene Blue Agar containing 2.0% NaCl (EMB-NaCl). When these injured cells were placed in fresh citrate salts medium they recovered, and regained their tolerance to the EMB-NaCl medium and grew out. The addition of the selective inhibitors rifamycin, 5-fluorouracil, 2,4-dinitrophenol, chlorotetracycline, chloramphenicol, and 5-methyl-tryptophan to the recovery medium showed that the recovery process was dependent on ribosomal ribonucleic acid (RNA) synthesis, adenosine triphosphate synthesis, and the synthesis of new protein. These results were substantiated by incorporation experiments, which demonstrated that during recovery no deoxyribonucleic acid synthesis, and hence no cell division, occurred. Ribosomal RNA was synthesized during recovery, but its synthesis was not the rate-limiting step. A small but significant amount of protein was also formed during the latter part of the recovery period.