Microbes Used to Clean Up Oil Spills
Naturally occurring microbes, mostly bacteria, but also fungi and some other organisms, consume oil for energy just as humans consume our familiar foods for the same purpose. Hundreds of millions of years of evolution in the presence of naturally occurring oil seepages have given them the ability to digest many, but not all, of the thousands of compounds in petroleum. While the idea of using microbes to help clean up man-made oil spills has its problems, genetic engineering may prove one answer.
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Evolution
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The rapidly improving science of DNA sequencing has revealed that oil-consuming bacteria are quite widespread on earth. Natural seepage of petroleum to the earth's surface -- on land and on the ocean floor -- occurs widely around the world. Estimates are that half the oil in the world's oceans results from this natural seepage. It is not surprising that some microbes have evolved to take advantage of this. While often thought of as a mineral, petroleum is in fact a biological substance -- the remains of algae and other plant material that died long ago and which time, heat and tremendous pressure over millions of years transformed into the precious commodity humans depend on for so much. The oil contains not just energy for cars, but food energy that some microbes use to live and flourish.
Energy
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Bacteria are the most common of the organisms that have developed the ability to digest, or degrade, oil for energy -- that is, to "eat" it as humans eat food -- though some types of fungi and other organisms can, too. In most instances, microbial degradation of oil occurs as microbes take in oxygen and "burn" the oil for energy. In some cases, though, the degradation occurs in anoxic fashion, without oxygen. This is important, because much of the remediation of oil spills in which humans are interested may take place in environments -- for example, salt marshes -- where anoxic conditions prevail.
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Oil
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While many microbes can consume oil, oil itself is a complex substance made up of tens of thousands of different compounds. Some portion of petroleum consists of volatile elements like methane and propane that evaporate quickly, saturated hydrocarbons that are more easily biodegraded and aromatic compounds, some of which are resistant to biodegradation. Resins containing nitrogen and sulfur are also common in oil. Some bacteria are capable of breaking down many of the hydrocarbons in oil, but no single organism is capable of cleaning up all the compounds in oil by itself. Most bacteria specialize in just a few hydrocarbons.
Bioremediation
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Using microbes to clean up oil spills, called bioremediation, sounds promising, but scientific studies have not shown that adding microbes to the site of an oil spill has ever helped accelerate the process of degrading the oil that occurs naturally, according to IEEE Spectrum. Part of the problem is that the communities of oil-eating microbes can't grow fast enough to respond before spills damage the environment. Oil-eating bacteria need additional nutrients to expand their populations, particularly nitrogen and phosphorous. But much of the coastal United States, where bioremediation would be most effective -- unlike in the open ocean -- already suffers from an overabundance of nitrogen and phosphorous caused by human pollution. Through genetic engineering, it may be possible to increase microbes' abilities to degrade oil. Bioremediation attempts may have other effects on the environment that are not clearly recognized.
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References
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