Effect of temperature on the cellular integrity of Bacillus psychrophilus

Abstract

The release of intracellular materials from the psychrophile Bacillus psychrophilus at temperatures from 5 to 50C was studied as a means of indicating possible membrane damage. RNA, protein, carbohydrate, and inorganic phosphate, but not DNA was found to leak from the cells. The rate of leakage increased as the temperature was raised. It is shown that the amount of leakage at 40C in the length of time required for 90% death could be sustained at 25C with little or no death. Therefore, death of this psychrophile at supramaximal temperatures cannot be attributed to loss of membrane integrity with resultant loss of intracellular material. Electron micrographs of the cells demonstrated a trilaminar cell wall which becomes severely damaged during heating. The damage is irreversible at 40C and may contribute to heat-induced death.