Thermodynamic conpensation in microbial thermal death. Studies with yeasts.

Sixty eight Arrhenius plots of thermal death in six mesophilic yeast species, tested at various concentrations of NaC1, lacked an isokinetic temperature. Nevertheless the deltaHnot equal to/deltaSnot equal to plot was apparently linear with a slope corresponding to 314degrees K. It was concluded the linear thermodynamic compensation of thermal death is non-existent in heterogeneous groups of yeasts and is unlikely to occur in hetero-geneous groups of other organisms and that deltaHnot equal to/deltaSnot equal to plots lack sensitivity for the detection of non-linearity over narrow temperature ranges. However, the deltaHnot equal to and deltaSnot equal to parameters of thermal death displayed non-linear compensation in such a way that the extrapolated Arrhenius plots of death attained nearly identical values near the respective maximum temperatures for growth. Linear thermodynamic compensation occurred in each of the six strains, when stationary populations of the same strain were tested at various NaC1 concentrations. On the other hand, exponential populations of each of the strains, tested in the same way, lacked an isokinetic temperature of thermal death. The significance of linear and non-linear thermodynamic compensation in biological rate processes is discussed.