Synthesis of protein and ribonucleic acid by starved Streptococcus lactis in relation to survival.

Abstract

SUMMARY Protein synthesis, as estimated from incorporation studies with [14C]valine, was barely detectable when organisms were starved in phosphate buffer containing Mg2+. The addition of an energy source promoted limited protein synthesis. In this respect glucose produced a much higher rate of [14C]valine uptake and incorporation than arginine. Although arginine prolonged survival, experiments with inhibitors showed that this was unlikely to be due to the protein synthesis which had been promoted. The ability of starved organisms to assimilate [14C]valine and to incorporate the isotope into protein in the presence of glucose appeared to be correlated with survival. Synthesis of RNA in starved organisms, as determined from [14C|uracil incorporation experiments, depended on exogenous glucose. During brief exposures to [14C]uracil plus glucose at intervals during starvation, organisms incorporated decreasing amounts of isotope into RNA although incorporation by non-viable organisms occurred at approximately half the initial rate. Although resynthesis of both protein and RNA was demonstrated with added energy sources, no evidence was obtained to suggest that this favoured survival.