Effects of Hyperbaric Pressure on a Deep-Sea Archaebacterium in Stainless Steel and Glass-Lined Vessels

Abstract

The effects of hyperbaric helium pressures on the growth and metabolism of the deep-sea isolate ES4 were investigated. In a stainless steel reactor, cell growth was completely inhibited but metabolic gas production was observed. From 85 to 100°C, CO2 production proceeded two to three times faster at 500 atm (1 atm = 101.29 kPa) than at 8 atm. At 105°C, no CO2 was produced until the pressure was increased to 500 atm. Hydrogen and H2S were also produced biotically but were not quantifiable at pressures above 8 atm because of the high concentration of helium. In a glass-lined vessel, growth occurred but the growth rate was not accelerated by pressure. In most cases at temperatures below 100°C, the growth rate was lower at elevated pressures; at 100°C, the growth rates at 8, 250, and 500 atm were nearly identical. Unlike in the stainless steel vessel, CO2 production was exponential during growth and continued for only a short time after growth. In addition, relatively little H2 was produced in the glass-lined vessel, and there was no growth or gas production at 105°C at any pressure. The behavior of ES4 as a function of temperature and pressure was thus very sensitive to the experimental conditions.

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

“…The effect of pressure on the physiology of hyperthermo-philic archaea is essentially unstudied, and little standardization of methodology is available. Nevertheless, the effects of various elevated pressures (hydrostatic and hypobaric) on such microorganisms have been reported (3,10,17,20,22,30,31,35,38). Growth was sometimes stimulated by increasing the pressure and the maximal temperature by a few degrees.…”

High-pressure, high-temperature bioreactor for comparing effects of hyperbaric and hydrostatic pressure on bacterial growth

“…4. Also presented for comparison are previous growth rates measured in the hyperbaric system before plating with gold (10). Plating the stainless steel with gold eliminated the previously reported inhibition of growth by steel (10).…”

“…At pressures greater than 50 atm, liquid samples were removed at regular intervals from both systems and decompressed as described previously (10). The loss in pressure due to sampling was made up by periodically adding He.…”

“…The interior of the hyperbaric system was treated in a similar fashion to minimize differences between the two systems. A glass liner can also be used with the hyperbaric system (10), but the liner does not completely eliminate liquid-steel contact. All wetted thermocouples and the steel ball were also gold plated.…”

“…ES4 is an extremely thermophilic chemoheterotroph isolated from a deep-sea hydrothermal vent environment (12). Artificial seawater medium was prepared as described elsewhere (10). Prior to each series of growth measurements, all reactor surfaces and tubing were sterilized with 70% ethyl alcohol before 30 g of So (rhombic, unsterilized) per liter was added to each vessel.…”