The Technology

DNA: Bioremediation involves GM0s - genetically modified microorganisms. Since they are genetically modified, the DNA between them will be very similar, and the traits between these organisms will stay consistent. Genetic engineering is the "process of manually adding new DNA to an organism," according to Agbiosafety. The goal is to add new desirable traits into the organism. In this case, some desired traits may be ones that make the organism more versatile for bioremediation - perhaps having it develop to work with more substances. 

Process: The actual process of bioremediation is very cool. Here are some diagrams so you can see how the process works: