Using DNA to track the bacteria’s unusual diet, UCSB scientists recently discovered bacteria feeding on natural gas leaking from the ocean floor at unusually cold temperatures at the site of the Deepwater Horizons oil spill in the Gulf of Mexico.
The research, published in the Proceedings of the National Academy of Sciences earlier this month, was led by UCSB professor, David Valentine, who was assisted by Molly Redmond, a postdoctoral scholar involved in the research. The National Science Foundation and the Department of Energy also participated in the project as part of their mission to understand how the oil spill disaster continues to affect the Gulf ecosystem.
The extensive depth and volume of the spill — predominantly comprised of methane, ethane and propane — allowed Valentine and Redmond to determine the role extreme temperature and natural gas play in bacterial ecosystems.
According to the report, “the colder temperature … [and] high natural gas content of this spill may have provided an advantage to these organisms.”
By June 2010 three bacterial species — Oceanospirillales, Colwellia and Cycloclasticus — residing in waters at 4 degrees Celsius and approximately 1,000 meters below the surface had already consumed the majority of the methane spilled.
Two months after consuming all of the methane, the hungry bacteria had also begun ingesting the remaining ethane and propane.
Redmond explained the effect of water temperature on the study’s unique findings in a recent press release.
“It’s much warmer at the surface than in the deep water — around 80 degrees [Fahrenheit] versus 40 degrees … There was very little natural gas in the surface samples, suggesting that both temperature and natural gas could be important in determining which bacteria bloomed after the spill. The bacteria we saw in the deep-water samples in May and June were related to types of psychrophilic, or cold-loving bacteria,” Redmond said. “Most bacteria grow more slowly at cooler temperatures — that’s why we keep our food in the refrigerator. But psychrophilic bacteria actually grow faster at cold temperatures than they would at room temperature.”
Valentine described how DNA was used to help determine the bacteria’s diet.
“They convert the alkenes into alcohols and get energy from that … the carbon provides cellular growth,” Valentine said. “We harvest the cells, harvest the DNA and separate the DNA using a density gradient in a centrifuge running at 100,000 rpm. The DNA goes to its spot depending on how heavy it is. We take about a dozen fractions, and we can distinguish the different kinds of DNA.”
According to Redmond, temperature is extremely important in the success of the bacteria since other organisms could not survive in such cold environments.
Furthermore, the bacteria’s ability to survive at such cold temperatures while simultaneously incorporating the byproducts of the spill into their diet was an unexpected finding.
“The fact that natural gas was so rapidly consumed was not anticipated,” Redmond said. “It’s so different.”