Mechanisms of Thermal Injury in Nonsporulating Bacteria

Abstract

Publisher Summary Because of the increasing use of heat sterilization and freezing methods of preservation of biological materials during the past 50 years, microbiologists are now giving considerable attention to the behavior of microorganisms at temperatures outside the limits of growth, while assessments of the efficiency of heat sterilization and pasteurization are being studied in depth. However, although moist and dry heat have been used as methods of sterilization for a considerable period of time, the reasons for this lack of knowledge are not too difficult to assess. The fact that vegetative bacteria are killed at low temperatures and spores at higher temperatures was, until recently, sufficient cause for using thermal processes without the necessity to carry out critical experiments to determine the nature of damages inflicted on the bacteria. This could be one reason for the often-repeated statement that moist heat kills vegetative bacterial cells by causing an intracellular coagulation of protein material. While such coagulation undoubtedly takes place to varying degrees, it is not unreasonable to propose that this effect masks other, more delicate, changes in the bacterial cell that could be induced before coagulation becomes apparent.