RELATIONSHIP BETWEEN THE THERMOTOLERANCE AND THE INCREASE OF DNAK ANDGROEL SYNTHESIS IN ENTEROCOCCUS-FAECALIS ATCC19433

Relationship between intrinsic thermal resistance, thermotolerance and heat shock proteins (hsp) synthesis is studied in Enterococcus faecal is. We showed that an impressive phenotypic heat resistance was induce d by mild heat and a slight thermotolerance was developed by various s ublethal pretreatments such as NaCl, SDS and bile salts. Hydrogen pero xide, acid and alkalin shifts or ''thermomimetic'' agent such as ethan ol, did not enhance the survival of adapted cells against the lethal t hermal shock (62 degrees C). The inhibition of protein synthesis by ch loramphenicol or rifampin abolished thermotolerance. The immunological identification of the DnaK and GroEL proteins in E. faecalis allowed to study induction of these molecular chaperones under various conditi ons. Heat was the most efficient inductor of DnaK and GroEL synthesis. However, it was surprising that ethanol did not strongly induce these proteins. We also show that amplification of these hsp is not correla ted to acquired thermotolerance with a linear relationship. A weak the rmotolerance is not coupled from increased synthesis of DnaK and GroEL . So, we postulate that the high synthesis of the major hsp is not obl igatory in the thermal cross-protection but that de novo protein synth esis is an absolute necessity in E. faecalis. Activation of preformed hsp or other factors depending or not on protein synthesis may be also necessary to enhance thermal resistance.