Induction of Thermotolerance by Split-dose Hyperthermia at 52°C in Deinococcus radiodurans

Abstract

The induction of thermotolerance by split-dose hyperthermia was analyzed in the radioresistant bacterium Deinococcus radiodurans wild type strain R₁. Immediately after a 30 min exposure to 52°C, the cells were maintained at 30°C for various intervals up to 6 hr in a medium and then exposed again to 52°C for various periods, that is, “split-dose hyperthermia.” Induced thermotolerance was maximum at the 4 hr interval. However, when chloramphenicol was added to the medium or the cells were incubated in a phosphate buffer, the thermotolerance induction decreased to the level of the survival curve without initial 52°C treatment. Also, when the cells previously heated were maintained at 42°C for 6 hr instead of 30°C, this tolerance induction was gently caused.

Therefore, these results suggest that proteins synthesized de novo during the interval incubation were involved either in the appearance of thermotolerance or in the recovery from the injury induced by 52°C heating for 30 min.