Re: What do the organisms used in oil spills do?

Your question was somewhat difficult to find answers. Most of the articles 
I've come across suggest that the microbes are a natural part of the 
environment.

Check this website: 
http://www.acnatsci.org/erd/ea/marine_oil.html

How are these organisms used all I read was that a colony is released.   
Is there any specific strategy?

Exxon Reports Effective Use Of Bioremediation In Valdez Spill
During a conference on in situ and on-site bioreclamation, Exxon senior 
staff scientist Roger Prince reported on the success of the use of 
fertilizers to remediate contamination from the Exxon Valdez oil spill. 
Exxon used two different fertilizers in the cleanup: Customblen™, a slow-
release solid fertilizer, and Inipol™, a microemulsion composed primarily 
of oleic acid.
The use of fertilizers as a means of bioremediation provides naturally 
occurring organisms with sufficient nutrients to break down the oil. 
Customblen™ was applied to subsurface areas and Inipol™ was applied 
to surface areas. Results obtained indicate that the treated areas had more 
oil-degrading organisms than untreated areas. However, the cumulative 
effects of fertilizer use is still under study. Although Inipol™ contains 
a biodegradable solvent, it is harmful to mammals before it degrades.
According to Prince, bioremediation "will probably be part of the toolbox 
to respond to any future spills." He concluded that the Prince William 
Sound cleanup effort provides "the first qualitative proof that 
bioremediation of oil spills really works."
Environment Reporter, Vol. 23, No. 51, April 16, 1993, p. 3169.

Here's another tidbit I've located.

The ability of microorganisms to degrade known mixtures of PCB congeners 
was assessed using bacteria found in contaminated sludge or soil. Of the 
several strains tested, two from contaminated soil, BTL331 and BTL333, 
degraded compound containing 2-5 chlorine atoms, except at the 4,4' 
position. Hexachlorobiphenyls were not degraded by these organisms. The 
other microorganisms, and the fungus Phanerochaete chrosysporum, were able 
to degrade the more stubborn congeners. Subculturing of organisms on media 
containing biphenyl enhanced degradation capability. The ability of four 
surfactants to desorb PCBs from sand was also studied. Triton X-100 was an 
efficre discussed. Type II methanotrophs are especially suitable for 
environmental remediation of chlorinated ethylene wastes. The ability of 
these organisms to degrade low molecular weight halogenated hydrocarbons 
is linked to the synthesis of soluble methane monooxygenase, which is 
regulated by copper concentration and the cell mass in a growing culture. 

I pulled this from another article specifying a bacteria.

Acinetobacter calcoaceticus RAG-1 is a marine bacteria which can utilize 
the hydrocarbons in oil as a source of carbon. When these bacteria are 
grown in a carbon minimal medium, they will breakdown hydrocarbons. RAG-1 
releases an emulsan - a polysaccharide that will emulsify oil. Emulsan 
accumulates on RAG-1 cell surfaces as minicapsules and is released into 
the media as an active emulsifier as the cell growth approaches the 
stationary phase. The absence of a carbon nutrient source accelerates the 
release of emulsans.

Good Luck with the research project.