Inactivation of Bacterial Spores by Hydrostatic Pressure

Abstract

SUMMARY: Spores of various species of the genera Bacillus and Clostridium were inactivated by hydrostatic pressures up to 8000 atmospheres. Inactivation was a function of holding time at pressure rather than of the compression and decompression stages. Inactivation generally proceeded more rapidly at high than at low temperatures; below about 50° there was a well defined optimum pressure for inactivation, but above about 50° an increase in pressure up to 8000 atmospheres caused progressively more inactivation. Inactivation was decreased at extremes of pH value and by high ionic strength solutions. A proportion of the spores pressurized under certain conditions became heat-sensitive. These observations, and the chemical, phase-contrast, and electron-microscopic changes seen in pressurized spores, suggested that pressure caused inactivation of spores by first initiating germination and then inactivating the germinated forms.