see how microbial activity changes over time as conditions change, and as cultured bacteria become incorporated into a microbial consortium. Finally, the lux genes signal scientists when the cleanup job is done. Where there are no more toxic molecules to find and degrade, the lights go out.

A great deal of research in environmental biotechnology is devoted simply to finding better ways of measuring and sampling the activities of microbes that might be potentially useful. It can take a lot of time and a lot of highly trained microbiologists to find the right microbes needed, for example, to degrade a particular pollutant. Only after the microbes are found can the task of genetic improvement proceed. To speed things up, many biotech companies are racing to develop more cost-effective and less labor-intensive ways of screening large numbers of bacteria. It's potentially a very lucrative field for those that succeed, as screening is the first step in developing most bioremediation programs.

A simple method recently tested quickly sorts out bacteria able to break down volatile organic compounds, such as carbon tetrachloride (used as cleaning fluid), toluene (an anti-knock agent added to gasoline), or xylene. The method consists of growing cultures of different bacteria on plates containing a dye. Eight dozen different cultures are grown on each plate, and the plates are exposed to chemical vapors in a sealed container. Bacteria that can degrade the contaminating fumes carry out oxidative reactions which, in turn, cause the dye to