Activity of prokaryotic communities from offshore oil reservoir and their adaptation to high hydrostatic pressure

Abstract

Deep-sea microbes comprise a significant portion of Earth’s biomass, but they are still poorly studied. Although the subseafloor is an oligotrophic, anoxic, dark, and pressurized environment, life still thrives in such kind of environment. In this work, three samples collected 100 m, 3,060 m, and 6,000 m deep in the Brazilian coast were investigated by analysis of 16S rRNA. A difference was found in the biological diversity between these communities at the genus level. The three communities had acid-producing bacteria and sulfate-reducing bacteria, but only the community from 3,060 m deep had a methanogenic archaeon. From the 6,000 m deep sample was isolated a bacterium of the Halanaerobium genus. Two important variables for the environment and offshore industries, bacterial survival, and hydrogen sulfide (H2S) production under high hydrostatic pressure (HHP) were investigated. Cell survival and H2S production were affected by HHP. In the case of the 3,060 m bacteria, population and H2S production increase with increasing pressure, while for the 100 m bacteria, population is stable with increasing pressure but H2S production decreases. The results show the importance of studying the influence of pressure on bacterial growth and H2S production to define strategies to mitigate economic losses arising from activities in marine environments.