Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples

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Abstract
Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3600 m depth) and southwest (4300 and 5200 m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67-0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3-5.degree. C and 360, 430 or 520 atm) were relatively slow, ranging from 0.09-0.39 nmol g-1 day-1; rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. Thus, microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure, and rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments.