Inducible thermotolerance in Lactobacillus bulgaricus

The effect of a sublethal heat challenge on the subsequent thermotolerance of Lactobacillus bulgaricus at different stages of growth was investigated along with the effect of heating menstrum on survival.
The response of the cells to heat stress was shown to be dependent upon both cell age and heating menstrum. Heat-inducible thermotolerance could be provoked in cells which had been growing exponentially when they were subjected to the sublethal heat stress: pre-incubation at 10^°C above the optimum growth temperature. The same effect could not, however, be reproduced in cells taken from the stationary phase.
Cells from the stationary phase were shown to always be more thermotolerant as compared to exponential phase cells. Cells showed a greater thermotolerance when heated in milk as compared to buffer.