Bacteria that love petroleum

Pseudomonas aeruginosaZoomZoom
© Richard Villemur, INRS-Institut Armand-Frappier

Article written by Julie Potvin-Barakatt and published in La revue des Cercles des Jeunes Naturalistes, July 2010.

Twenty days after the explosion of the Deepwater Horizon oil platform on April 20, 2010, it was estimated that nearly 10 million liters of petroleum had accumulated in the Gulf of Mexico. And every day since then, nearly 800,000 additional liters have been added to the oily pool. This deplorable episode is reminiscent of the sinking of the Exxon Valdez in 1989, which caused the release of 42 million liters of petroleum in Alaska. Such environmental catastrophes require rapid intervention in order to limit the damage inflicted by the petroleum on the local flora and fauna. Did you know that, in addition to initiating controlled combustion and spreading chemical dispersants, one can also count on the action of certain bacteria?

Oceans are full of bacteria, all of which play different roles in maintaining the equilibrium of these ecosystems. Luckily, some bacteria are able to feed on petroleum, transforming it into less toxic compounds. These bacteria are present in minute quantities, but as soon as their favorite meal becomes readily available, they multiply rapidly, with great numbers of them partaking together in this somber feast. One can balance their menu by adding phosphorus and nitrogen in order to optimize their cleaning action. As soon as the petroleum has been consumed, the concentration of bacteria decreases to its initial value because they become less competitive and are vulnerable to predation by other marine organisms.

How do these black gold degradation champions find their way into the oceans? Note that in addition to these large-scale accidental spills, nearly 1.5 billion liters of petroleum are introduced annually into the oceans either deliberately or incidentally. This diluted petroleum, distributed throughout all the oceans, is enough to ensure the presence of the bacteria that it feeds but constantly keeps on a diet.

Problem solved? Not completely. « In a few weeks, between 75 and 85% of the petroleum spilt in the Gulf of Mexico will be eliminated by evaporation and by bacteria, but the rest will persist in sediments in the bottom of the ocean and in marshes for years, » explains Émilien Pelletier, a professor of marine eco-toxicology at the Institut des sciences de la mer in Rimouski (ISMER). The famished bacteria can only gorge on petroleum in the presence of oxygen, which is very rare in these environments.

Could we help these marine bacteria by accelerating the degradation of the petroleum before it sinks to the bottom? This is what many researchers have been working on for decades. They culture these petroleum-eating bacteria in the laboratory to add them to the black tides. This expensive strategy has not been effective to date, because these laboratory-raised strains of bacteria are more fragile and have difficulty surviving in the natural environment. Research continues.

Scientists around the world continue to expand their knowledge of these bacteria able to feed off petroleum. The more we understand them, the better we will be able to use their appetite to our advantage. Their soft spot for petroleum is a sweet indulgence indeed!