ENHANCED THERMOTOLERANCE BY HYDROSTATIC-PRESSURE IN THE DEEP-SEA HYPERTHERMOPHILE PYROCOCCUS STRAIN ES4

The combined effect of hydrostatic pressure and heat shock on thermoto lerance was examined in the deep-sea hyperthermophilic archaeon Pyroco ccus strain ES4. Pressure equivalent to the depth of isolation (22 MPa ) enhanced ES4's survival at super-optimal temperatures (101-108 degre es C) relative to low pressure (3 MPa). Pressure also raised the tempe rature at which a putative heat-shock protein (98 kDa) accumulated. ES 4 grown at 95 degrees C and 3 MPa displayed immediate enhanced thermot olerance to 105 degrees C after being shifted to 22 MPa. Cultures grow n at 95 degrees C and 22 MPa and then heat shocked at 105 degrees C an d 3 MPa retained enhanced thermotolerance after decompression. These r esults suggest that this deep-sea hyperthermophile has developed press ure-induced responses that include increased survival to hyperthermal conditions.