Effect of Elevated Pressure on Microbial Communities from the Gulf of Mexico

The Deepwater Horizon incident in 2010 released an unprecedented amount of petroleum hydrocarbons from the wellhead at 1500 meter depth, at which hydrostatic pressure is 15 MPa. So far few studies have considered the influence of hydrostatic pressure on bacterial community development and activity during such spills, The goal of this study was to investigate the response of indigenous sediment microbial communities to hydrostatic pressure, hydrocarbons and dispersant. Deep-sea sediment samples collected from the northern Gulf of Mexico were incubated at atmospheric pressure (0.1 MPa) and at elevated pressure (10 MPa), with and without the addition of crude oil and dispersant. After incubations at 4?C for 7 days, Gammaproteobacterial members of Colwellia and Psychrobium were highly abundant in all samples. Pressure differentially impacted members of the Alteromonadales. Alterations in the bacterial community composition were most pronounced when dispersant was added to the incubation. Moritella and Thalassotalea were greatly stimulated by the addition of dispersant at atmospheric pressure. Moritella was negatively impacted by hydrostatic pressure, while Thalassotalea was not affected by hydrostatic pressure. Cycloclasticus was stimulated by pressure and was inhibited by dispersant. This study highlights the significant influence of pressure on microbial communities developing during oil spills in the deep sea.