The thermal inactivation kinetics of @entity10435 PT4 between 49 and 60 degrees C were investigated. Using procedures designed to eliminate methodological artifacts, we found that the death kinetics deviated from the accepted model of first-order inactivation. When we used high-density stationary-phase populations and sensitive enumeration, the survivor curves at 60 degrees C were reproducibly biphasic. The decimal reduction time at 60 degrees C (D60 degrees C) of the tail subpopulation was more than four times that of the majority population. This difference decreased with decreasing temperature; i.e., the survivor curves became more linear, but the proportion of tail cells remained a constant proportion of the initial population, about 1 in 10(4) to 10(5). Z plots (log D versus temperature) for the two populations showed that the D values coincided at 51 degrees C, indicating that the survivor curves should be linear at this temperature, and this was confirmed experimentally. Investigations into the nature of the tails ruled out genotypic differences between the populations and protection due to leakage from early heat casualties. Heating of cells at 59 degrees C in the presence of 5 or 100 micrograms of @entity2755 per ml resulted in reductions in the levels of tailing. These reductions were greatest at the higher @entity2755 concentration. Our results indicate that de novo protein synthesis of @entity1457 proteins is responsible for the observed tailing. Chemostat-cultured cells heated at 60 degrees C also produced biphasic survivor curves in all but one instance. Cells with higher growth rates were more heat sensitive, but tailing was comparable with batch cultures. Starved cells (no dilution input) displayed linear inactivation kinetics, suggesting that during starvation a rapid @entity1457 response cannot be initiated.

Biphasic thermal inactivation kinetics in XXXX PT4.

@entity1457 :: ('MESH:D012769', 'Disease') :: ['heat shock'] @entity2755 :: ('MESH:D002701', 'Chemical') :: ['chloramphenicol'] @entity10435 :: ('149539', 'Species') :: ['Salmonella enteritidis']
@entity10435 :: (149539,Species) :: ['Salmonella enteritidis']
