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 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 reserves. Moribund and dead cell populations showed an elevated level of intracellular adenosine-5'-triphosphate and amino acids-a finding reflected in the reduced rate of amino acid synthesis during the recovery of heat-shocked cells-and also leakage of degraded ribonucleic acid products into the medium. Incorporation studies indicated that loss of viability at 30 C was correlated with inhibition of protein synthesis, followed later by inhibition of ribonucleic acid synthesis. Deoxyribonucleic acid synthesis was unaffected by temperature above the maximum.

Psychrophilic bacteria.

“…However, as they point out, this does not account for the decline in the growth of the organism between the optimum and maximum growth temperatures. When a cell-free extract prepared from the psychrotrophic bacterium Micrococcus cryophilus was subjected to 5 C above the maximal growth temperature for the organism, three aminoacyl-tRNA synthetases (glutamic acid, histidine, and proline) were found to be temperature sensitive (109,110,111,112). Unfortunately, the experiments were not carried out 1 or 2 C above the maximal growth temperature for M. cryophilus.…”

The elongation of exogenous fatty acids and the control of phospholipid acyl chain length in Micrococcus cryophilus

“…It was possible, therefore, that the inhibition of phospholipid acyl chain elongation in M. cryophilus was a secondary effect resulting from a decrease in ATP and reduced nicotinamide nucleotide concentrations, which would be a consequence of the inhibition of tricarboxylic acid-cycle activity. M. cryophilus grows aerobically and contains enzymes of the tricarboxylic acid cycle (Malcolm, 1968). To investigate this possibility the effect on fatty acid synthesis and elongation of sodium malonate, an inhibitor of succinate dehydrogenase Isuccinate-(acceptor) oxidoreductase; EC 1.3.99.1] was determined; the activity of succinate dehydrogenase was used as an indicator of tricarboxylic acid-cycle activity.…”