SUMMARY: The death-rate of washed exponential phase chilled in saline phosphate buffer (pH 6.5) at 0° was increased by ribonuclease (RNase) but not by deoxyribonuclease, trypsin, pepsin or lysozyme; none of these enzymes had any immediate effect on the viability of similar bacterial suspensions at 20°. Leakage products from chilled , Mg+ and, to a smaller extent, 0.3M-sucrose, antagonized the lethal effect of RNase on chilled organisms. RNA degradation occurred when bacteria were chilled and then incubated in fresh diluent at 37°; organisms exposed to RNase during chilling degraded RNA at 20-25° when the rate of auto-degradation of RNA was low. As the salt content of the environment was decreased, the amount of RNase adsorbed by the bacteria and its lethal effect increased at both 0° and 20°; in distilled water RNase was more lethal at 20° than at 0°. Anilino-naphthalene-8-sulphonate penetrated into bacteria chilled in buffer containing this dye. Acid or alkali accelerated the death rate of bacteria to greater extents at 0° than at 20°. RNase increased the lethal effect of freezing and thawing on a population from a continuous culture and augmented subsequent degradation of RNA.


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