Physiological Responses to Stress Conditions and Barophilic Behavior of the Hyperthermophilic Vent Archaeon Pyrococcus abyssi

Abstract

The physiology of the deep-sea hyperthermophilic, anaerobic vent archaeon Pyrococcus abyssi, originating from the Fiji Basin at a depth of 2,000 m, was studied under diverse conditions. The emphasis of these studies lay in the growth and survival of this archaeon under the different conditions present in the natural habitat. Incubation under in situ pressure (20 MPa) and at 40 MPa increased the maximal and minimal growth temperatures by 4؇C. In situ pressure enhanced survival at a lethal high temperature (106 to 112؇C) relative to that at low pressure (0.3 MPa). The whole-cell protein profile, analyzed by one-dimensional sodium dodecyl sulfate gel electrophoresis, did not change in cultures grown under low or high pressure at optimal and minimal growth temperatures, but several changes were observed at the maximal 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 different temperatures was analyzed by thin-layer chromatography. The phospholipids became more complex at a low growth temperature at both pressures but their profiles were not superimposable; fewer differences were observed in the core lipids. The polar lipids were composed of only one phospholipid in cells grown under in situ pressure at high temperatures. Survival in the presence of oxygen and under starvation conditions was examined. Oxygen was toxic to P. abyssi at growth range temperature, but the strain survived for several weeks at 4؇C. The strain was not affected by starvation in a minimal medium for at least 1 month at 4؇C and only minimally affected at 95؇C for several days. Cells were more resistant to oxygen in starvation medium. A drastic change in protein profile, depending on incubation time, was observed in cells when starved at growth temperature.

Temporal and spatial archaeal colonization of hydrothermal vent deposits

“…Microbial 16S rRNA genes detected in our Guaymas subsamples (Methanocaldococcus at 110°C and Desulfurococcaceae at 116°C) were likely exposed to lethal temperatures, as the highest temperature for growth of Methanocaldococcus cultures is 92°C (M. fervens, Jeanthon et al, 1999), and only one Desulfurococcaceae isolate appears to grow at 116°C (Kashefi and Lovley, 2003). These results support studies suggesting that microorganisms colonizing high-temperature deposits can survive at temperatures above their known maximum temperature for growth under high pressures and constant supplies of carbon and energy sources (Miller et al, 1988;Marteinsson et al, 1997;Lloyd et al, 2005;Edgcomb et al, 2007). The large temperature fluctuations recorded within the outer 1 cm of BM4 (Fig.…”

High hydrostatic pressure adaptive strategies in an obligate piezophile Pyrococcus yayanosii

“…It was grown at 98 °C under anaerobic conditions in TRM medium (“ Thermococcales Rich Medium”) 10 . High hydrostatic pressure cultures were grown in sterile syringes and incubated in a high hydrostatic pressure/high-temperature incubator (Top Industrie) from 0.1 MPa to 80 MPa, as previously described 48 . Once the middle of the exponential phase was reached (after 4 hours), the cells were slowly decompressed and immediately placed in previously frozen falcon tubes, in order to minimize the degradation of the cell component (RNA and proteins).…”

Restoration of the di-myo-inositol-phosphate pathway in the piezo-hyperthermophilic archaeon Thermococcus barophilus

“…Hydrothermal vents are characterized by large temperature fluctuations from fluid temperatures as high as 400°C (Cayman Trough, Western Caribbean Sea) at the heart of the vent, to 2°C, the average temperature of the surrounding deep ocean waters [1]. Due to this extremely steep gradient and the fluctuating environment, it is expected that microorganisms from hydrothermal vents express a strong thermal stress response [8][9][10]. In a simplistic view, the effects of heat stress on cells and cell structures can be explained by a single factor, e.g.…”

“…barophilus strain MP grows from ca. 65°C to 95°C at atmospheric pressure, and up to 100°C at 40MPa, with an optimum at 85°C at both pressures[9]. To optimize thermal stress conditions, T. barophilus was grown in TRM[31] at varying temperatures ranging form 65°C to 98°C under optimal pressure and salinity conditions, e.g 40 MPa and 3% NaCl.…”