PRESSURE AND TEMPERATURE EFFECTS ON GROWTH AND VIABILITY OF THE HYPERTHERMOPHILIC ARCHAEON THERMOCOCCUS-PEPTONOPHILUS

We studied the effects of high temperatures and elevated hydrostatic p ressures on the physiological behavior and viability of the extremely thermophilic deep-sea archaeon Thermococcus peptonophilus. Maximal gro wth rates were observed at 30 and 45 MPa although no significant incre ases in cell yields were detected. Growth at 60 MPa was slower. The op timal growth temperature shifted from 85 degrees C at 30 MPa to 90-95 degrees C at 45 MPa. Cell viability during the stationary phase was al so enhanced under high pressure. A trend towards barophily at pressure s greater than those encountered in situ at the sea floor was demonstr ated at increasing growth temperatures. The viability of cells during starvation, at high temperature (90, 95 degrees C), and at low tempera ture (10 degrees C) was enhanced at 30 and 45 MPa as compared to atmos pheric pressure. These results show that the extremely thermophilic ar chaeon T. peptonophilus is a barophile.