Bioremediation uses natural as well as recombinant (genetically engineered) microorganisms to break down toxic and hazardous substances present in the environment because of some human activity.

Huge numbers of bacteria exist naturally in the soil and the rubbish in recycling and land-fill sites. Some of those bacteria slowly break down the many different types of waste. Some bacteria use oil as a source of nutrients just as we use food. These bacteria can be used to break down oil spills at sea or on the shore.

Biological treatment to solve waste or hazardous chemical problems is not a new idea. What is new is the greatly increased range of biotreatments that may be made possible by biotechnology. Biotechnologists can use gene technology to recombine, or mix and match, the most desirable traits of several bacterial species to create recombinant (genetically engineered) varieties. In the future they could, perhaps, extract the gene from one strain that allows it to break down some specific hazardous waste and the gene from another that allows it to withstand wide temperature ranges, lack of oxygen or another environmental extreme. These genes could then be transferred into a common, harmless bacterium that can be easily mass produced. The ideal result is a bacterium genetically custom-made to clean up a specific problem waste at a particular site under defined conditions.