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Abstract
The death-rate of washed exponential phase Aerobacter aerogenes chilled in saline phosphate buffer (pH 6·5) at 0° was increased by ribonuclease (RNase) but not by deoxyribonuclease, trypsin, pepsin or lysozyme; noneof these enzymes had any immediate effect on the viability of similar bacterial suspensions at 20°. Leakage products from chilled A. aerogenes, Mg2+ and, to a smaller extent, 0·3 m-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 autodegradation 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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