Microbial communities present in the Gulf of Mexico rapidly
responded to the Deepwater Horizon oil spill. In deep water
plumes, these communities were initially dominated by members
of Oceanospirillales, Colwellia, and Cycloclasticus. None of these
groups were abundant in surface oil slick samples, and Colwellia
was much more abundant in oil-degrading enrichment cultures incubated
at 4 °C than at room temperature, suggesting that the
colder temperatures at plume depth favored the development of
these communities. These groups decreased in abundance after the
well was capped in July, but the addition of hydrocarbons in laboratory
incubations of deep waters from the Gulf of Mexico stimulated
Colwellia’s growth. Colwellia was the primary organism that
incorporated 13C from ethane and propane in stable isotope probing
experiments, and given its abundance in environmental samples
at the time that ethane and propane oxidation rates were high,
it is likely that Colwellia was active in ethane and propane oxidation
in situ. Colwellia also incorporated 13C benzene, and Colwellia’s
abundance in crude oil enrichments without natural gas suggests
that it has the ability to consume a wide range of hydrocarbon
compounds or their degradation products. However, the fact that
ethane and propane alone were capable of stimulating the growth
of Colwellia, and to a lesser extent, Oceanospirillales, suggests
that high natural gas content of this spill may have provided an
advantage to these organisms.