Hydrocarbon-degradation and MOS-formation capabilities of the dominant bacteria enriched in sea surface oil slicks during the Deepwater Horizon oil spill

A distinctive feature of the Deepwater Horizon (DwH) oil spill was the formation of significant quantities of marine oil snow (MOS), for which the mechanism(s) underlying its formation remain unresolved. Here, we show that Alteromonas strain TK-46(2), Pseudoalteromonas strain TK-105 and Cycloclasticus TK-8 - organisms that became enriched in sea surface oil slicks during the spill - contributed to the formation of MOS and/or dispersion of the oil. In roller-bottle incubations, Alteromonas cells and their produced EPS yielded MOS, whereas Pseudoalteromonas and Cycloclasticus did not. Interestingly, the Cycloclasticus strain was able to degrade n-alkanes concomitantly with aromatics within the complex oil mixture, which is atypical for members of this genus. Our findings, for the first time, provide direct evidence on the hydrocarbon-degrading capabilities for these bacteria enriched during the DwH spill, and that bacterial cells of certain species and their produced EPS played a direct role in MOS formation.