9-2 |
|
P. SETLOW, Molecular Biology and Biochemistry Program, Univ. of Connecticut Health Center, 263 Farmington Ave., UCHC-3305, Farmington, CT 06030 The first step in the killing of spores of Bacillus and Clostridium species by high pressures is the triggering of spore germination; this is followed by inactivation of the more sensitive germinated spores, generally by heat. Since spore germination is essential for efficient spore killing by pressure treatments, it is important to identify the factors that determine the rate of spore germination triggered by high pressures. Consequently, in this presentation I will describe studies of the germination of B. subtilis spores by both low (150 MPa) and high (500 MPa) pressures, examining the role of factors that affect spore germination with other agents including nutrients, Ca2+-dipicolinic acid (DPA) and cationic surfactants. Specific factors that have been tested for their effects on pressure germination include: 1) the level of receptors for nutrient germinants in the dormant spore's inner membrane; 2) individual nutrient germinant receptors that normally respond to very different nutrients; 3) covalent lipid addition to nutrient germinant receptors; 4) the absence of one or both of the two redundant lytic enzymes that normally initiate the hydrolysis of the spore's peptidoglycan cortex during germination; 5) the absence of the spore's large depot (~10% of dry wt) of DPA; 6) the sporulation temperature which will likely modulate the fluidity of the spore's inner membrane; 7) levels of unsaturated fatty acids in the spore's inner membrane; 8) pretreatment of spores with oxidizing agents that appear to damage the spore's inner membrane; and 9) inhibitors of spore germination with nutrients. The results of these studies and those from other labs on this topic will be summarized and models will be presented illustrating the mechanisms whereby both low and high pressures may trigger spore germination.
Session 9, Mechanisms and modeling of bacterial spore inactivation by high pressure processing
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |