Ocean Pollution Makes Microbes Adapt – GWC Mag

For several hot July days in 2016, microbiologist Sabine Matallana-Surget swam in the waters near Pensacola Beach, Fla., with plastic bags full of seawater, crude oil, and a cleaning agent called Corexit. By floating these materials on the Gulf of Mexico’s surface, she simulated the marine environment as it existed during the 2010 Deepwater Horizon disaster.

In the wake of that environmental catastrophe, airplanes dumped nearly 2 million gallons of Corexit on the Gulf of Mexico to break up the slick. Its effect on the oil-eating bacteria that ultimately cleaned the ecosystem of contaminants is largely unknown.

By deploying her carefully curated bags, Matallana-Surget, an associate professor in environmental molecular microbiology at the University of Stirling, was working to incubate microbial communities and see how they developed in the first 24 hours after exposure to crude oil, Corexit, and large doses of ultraviolet (UV) radiation.

“It didn’t create an incredibly toxic soup. But it wasn’t harmless either.”

Current studies have shown that the Roseobacteraceae family of bacteria put the b in biodegradable. They have an appetite for hydrocarbon and ought to proliferate in the wake of an oil spill—at least in theory.

But “just because it happens in the lab doesn’t mean it will work in the field,” cautioned Wade Jeffrey, director of the Center for Environmental Diagnostics and Bioremediation at the University of West Florida and a coauthor of the paper published in Frontiers in Marine Science. “You could grow cultures of bacteria in the lab that would eat anything. In the natural world, that doesn’t work the same because there’s lots of other things that are easier to eat than these complex organic compounds,” he said.

To examine what happened inside the bags, Matallana-Surget borrowed a technique from medical science that checks bacterial health by profiling their DNA-expressed proteins.

“We didn’t have any idea how the UV and the oil and the Corexit were all going to interact. It didn’t create an incredibly toxic soup. But it wasn’t harmless either,” Jeffrey said.

Environmental Dependencies

In the field, some bacteria showed a remarkable ability to produce oil-digesting enzymes in all conditions, whether under intense UV radiation, shocked with Corexit, or both.

In particular, species in the orders Alteromonadales and Oceanospirillales flourished by virtue of several different adaptations. Their efficient DNA repair mechanisms, tolerance of oxidative stress, and omnivorous capacity to metabolize different food sources gave them an advantage over bacteria that didn’t fare as well, like Roseobacter, which had performed well in the lab.

Rhodovulum, another common oil degrader, succumbed to UV radiation, whereas others perished because of Corexit and did so in a fashion that surprised Matallana-Surget.

“I study a lot of different stressors, and I’ve never seen that many stressors when it comes to the DNA damage induced by Corexit,” she said.

Zhanfei Liu, a professor of marine science at the University of Texas at Austin, applauded Matallana-Surget’s use of protein sequencing to reveal how some bacteria survive and thrive. “This work is a major contribution to the field, and in addition to oil spill science, it also offers insights into how microorganisms work in marine environments,” he said.

Matallana-Surget said policymakers should start asking questions like, Will sunlight impact and modify the chemicals we already have in the sea? Is the spill in a place where you already have some bacteria that are naturally present and could potentially degrade the oil? Do we add tons of Corexit or just enough to biodegrade the oil? She hopes her findings lead to more informed disaster mitigation strategies.

—Martin J. Kernan, Science Writer

Citation: Kernan, M. J. (2024), Ocean pollution makes microbes adapt, Eos, 105, https://doi.org/10.1029/2024EO240123. Published on 18 March 2024.

Text © 2024. The authors. CC BY-NC-ND 3.0
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