Bacteria Naturally 'Eat Up' Oil Spill Contamination by Supplementing Diet with Nitrogen

The discovery that bacteria living in the Gulf of Mexico beaches "ate up"' the contamination leaked from the Deep Water Horizon oil spill by supplementing their diet with nitrogen could lead to far more sophisticated cleanup techniques, researchers say.

Led by Joel Kostka, a microbiologist from Georgia Institute of Technology, a new study presented to delegates at the Goldschmidt conference explains that because oil is a natural product comprised of decayed plants and animals, it's similar to what bacteria are already accustomed to consuming.

"But because oil is low in nutrients such as nitrogen, this can limit how fast the bacteria grow and how quickly they are able to break down the oil," Kostka said in a statement. "Our analysis showed that some bacteria are able to solve this problem themselves -- by getting their own nitrogen from the air."

Kostka worked with Markus Huettel, a biogeochemist from Florida State University, to analyze more than 500 samples taken over a two-year period from Pensacola beach in the Gulf of Mexico, starting when the Deep Water Horizon oil slick first came ashore in June 2010.

By examining every gene belonging to the bacteria found in the different samples, they were able to determine which bacteria were present and how they responded as conditions changed on the beach. Specifically, the scientists studied the prevalence of genes responsible for encoding for different behaviors, including nitrogen fixing, in order to decipher exactly how the bacteria were breaking down the oil.

"By understanding how the oil is degraded by microbes, which microbes do the work, and the impact of the surrounding environmental conditions, we can develop ways to intervene to support the natural clean-up process," Kostka said.

For instance, knowing exactly how the oil-degrading bacteria are working in different areas affected by a spill make it possible to identify those beaches that are least equipped to self-clean and thus where mitigation efforts are needed most.

However, Kostka warns, any kind of human intervention in this natural clean up process must be carried out "in a very measured and targeted way, to avoid long-term, unintended damage to the ecosystem. For example, in the past, nitrogen [fertilzer] has been sprayed onto contaminated beaches to speed up the work of the bacteria. Our analysis shows that, where bacteria can get this nitrogen naturally, such drastic intervention may not be necessary."  

Furthermore, the research showed that not all bacteria thrived on a high-oil diet, with some bacteria that played an important role in the affected beaches' ecosystems sharply declining following the June 2010 contamination.

"There's a tendency to focus on the short-term, visible effects of an oil spill on the beach and assume that once the beach looks 'clean' then all is back to normal," Kostka said. "Our analysis shows some of the invisible impact in the loss of these important microbes. We need to be aware of the long-term chronic damage both a spill -- and in some cases our attempts to deal with it -- can cause."