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

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Abstract
When an E. coli K-12 culture was starved for glucose, 50% of the cells lost viability in .apprx. 6 days. When a K-12 mutant lacking 5 distinct peptidase activities, CM89, was starved in the same manner, viability was lost much more rapidly; 50% of the cells lost viability in .apprx. 2 days. A parent strain lacking 1 peptidase activity lost 50% viability in .apprx. 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 C starvation. Similar results were obtained with glucose-starved S. typhimurium LT2 and LT2-derived mutants lacking various peptidase activities. An S. typhimurium mutant lacking 4 peptidases, TN852, which was deficient in both protein degradation and synthesis during C starvation, was .apprx. 1/3 as stable as the isogenic wild-type. Isogenic S. typhimurium strains that lacked various combinations of 3 of 4 peptidases and that displayed protein degradation and synthesis rates intermediate between those of LT2 and TN852 displayed corresponding stabilities during C starvation. These results point to a role for protein degradation in the survival of bacteria during C starvation.