| MadSci Network: Microbiology |
Some bacteria are able to use the organic molecules found in crude oil as a carbon, or energy, source. They use it instead of using simple sugars, such as glucose, which most other bacteria use.
What happens is that these bacteria have enzymes that can take these molecules and convert them into simpler compounds in a couple of steps, using specific enzymes the bacteria produce. The organic molecules in oil (these are often long chain alkane molecules, like octane which is an 8 carbon chain) are converted to something that the bacteria would naturally use, something similar to a sugar which is often a 6 chain carbon molecule.
The basic process used in decomposition or bioremediation is generally the same. A specific enzyme that recognizes the contaminant and converts it to something that is more common and which the bacteria can then use as food and grow on.
The second part to your question is more difficult to answer. Many bacteria that decompose oil can be used both in soil and in water spills. But not all. It isn't so much the water vs soil problem, but rather other things. For example, once you get below the top surface, there is little oxygen present in deep soil for bacteria to use.