Synthesis of Protein and Ribonucleic Acid in a Psychrophile at Normal and Restrictive Growth Temperatures

Abstract

A defined medium was capable of supporting the growth of a psychrophilic coccus rMicrococcus cryophilus] over its growth temperature range, -4 to 25 C. A rapid loss of viability occurred when exponential cells were transferred to growth-restricting temperatures above 25 C. Comparative studies of the chemistry of exponential-phase cells and cells exposed to supermaximum temperature indicated that this loss of viability is not due to temperature-induced membrane damage, inhibition of respiration or energy metabolism or depletion of intracellular reverses. Moribund and dead cell populations showed an elevated level of intracellular adenosine-5''-triphosphate and amino acids[long dash]as indicated by the reduced rate of amino-acid synthesis during the recovery of heat-shocked cells and leakage of degraded RNA products into the medium. Loss of viability at 30 C may be correlated with inhibition of protein synthesis, followed by inhibition of RNA synthesis. The DNA synthesis was unaffected by a temperature above the maximum.