Although many bacteria have dietary requirements similar to ours—that’s why they cause food spoilage—others metabolize (or chemically process) substances that are toxic to most plants and animals: heavy metals, sulfur, petroleum, and mercury. Oil in the environment can come from natural oil that seeps from petroleum deposits, and it can also come from oil spills. Although there are oil-degrading bacteria in soil and sediments, these bacteria are in such small numbers that they cannot deal with large-scale contamination efciently.
Scientists are now working to improve the eficiency of natural pollution fighters. Using bacteria to degrade pollutants is called bioremediation. One of the most promising successes for bioremediation occurred on an Alaskan beach following the Exxon Valdez oil spill in 1989. Several naturally occurring Pseudomonas bacteria are able to degrade oil for their carbon and energy requirements. In the presence of air, they remove two carbon atoms at a time from a large petroleum molecule (see the figure).
The bacteria degrade the oil too slowly to clean up an oil spill. However, scientists hit on a very simple way to speed up the process: they simply dumped ordinary nitrogen and phosphorus plant fertilizers (bioenhancers) onto a test beach. The number of oil-degrading bacteria increased compared with that on unfertilized control beaches, and oil was quickly cleared from the test beach.
This technique works on land but has not been studied in open water. A number of questions need to be addressed: Will the fertilizer stay near the oil? Will the fertilizers
stimulate toxic algae?
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