Role of protein degradation in the survival of carbon-starved Escherichia coli and Salmonella typhimurium

When an Escherichia coli K-12 culture was starved for glucose, 50% of the cells lost viability in about 6 days. When a K-12 mutant lacking five distinct peptidase activities, CM89, was starved in the same manner, viability was lost much more rapidly; 50% of the cells lost viability in about 2 days, whereas a parent strain lacking only one peptidase activity lost 50% viability in about 4 days. Compared with the wild-type strain and with its parent strain CM17, CM89 was defective in both protein degradation and protein synthesis during carbon starvation. Similar results were obtained with glucose-starved Salmonella typhimurium LT2 and LT2-derived mutants lacking various peptidase activities. An S. typhimurium mutant lacking four peptidases, TN852, which was deficient in both protein degradation and synthesis during carbon starvation (Yen et al., J. Mol. Biol. 143:21-33, 1980), was roughly one-third as stable as the isogenic wild type. Isogenic S. typhimurium strains that lacked various combinations of three of four peptidases and that displayed protein degradation and synthesis rates intermediate between those of LT2 and TN852 (Yen et al., J. Mol. Biol. 143:21-33, 1980) displayed corresponding stabilities during carbon starvation. These results point to a role for protein degradation in the survival of bacteria during starvation for carbon.