PHYSIOLOGICAL-RESPONSES TO STRESS CONDITIONS AND BAROPHILIC BEHAVIOR OF THE HYPERTHERMOPHILIC VENT ARCHAEON PYROCOCCUS-ABYSSI

The physiology of the deep-sea hyperthermophilic, anaerobic vent archa eon Pyrococcus abyssi, originating from the Fiji Basin at a depth of 2 ,000 m, was studied under diverse conditions, The emphasis of these st udies lay in the growth and survival of this archaeon under the differ ent conditions present in the natural habitat. Incubation under in sit u pressure (20 MPa) and at 40 MPa increased the maximal and minimal gr owth temperatures by 4 degrees C, In situ pressure enhanced survival a t a lethal high temperature (106 to 112 degrees C) relative to that at low pressure (0.3 MPa), The whole-cell protein profile, analyzed by o ne-dimensional sodium dodecyl sulfate gel electrophoresis, did not cha nge in cultures grown under low or high pressure at optimal and minima l growth temperatures, but several changes were observed at the maxima l growth temperature under in situ pressure, The complex lipid pattern of P. abyssi grown under in situ and 0.1- to 0.5-MPa pressures at dif ferent temperatures was analyzed by thin-layer chromatography. The pho spholipids became more complex at a low growth temperature at both pre ssures but their profiles were not superimposable; fewer differences w ere observed in the core lipids. The polar lipids were composed of onl y one phospholipid in cells grown under in situ pressure at high tempe ratures. Survival in the presence of oxygen and under starvation condi tions was examined. Oxygen was toxic to P. abyssi at growth range temp erature, but the strain survived for several weeks at 4 degrees C, The strain was not affected by starvation in a minimal medium for at leas t 1 month at 4 degrees C and only minimally affected at 95 degrees C f or several days, Cells were more resistant to oxygen in starvation med ium, A drastic change in protein profile, depending on incubation time , was observed in cells when starved at growth temperature.