Figure 5.2

A researcher counts colonies of "reporter" bacteria that fluoresce and are used as a monitor for bacterial cleanup of oil-polluted soils.

through fiber-optic sensors. Being able to study the activity of pollution-fighting bacteria at work in the field in real time is a great advantage, eliminating the need for "best guess" predictions and labor-intensive experiments. It allows scientists to quickly analyze an organism's efficiency and to optimize it, for example by adjusting nutrient levels to boost bacterial growth.

Most current work involving microorganisms in the field uses naturally occurring species, since there is concern over the release of genetically altered microbes into the environment. In controlled field experiments using microbes engineered with lux genes, it is possible to literally watch the spread of engineered genes through the population as the microbes multiply, and to monitor the degree of transfer of these genes from the lab strain to native varieties. This new technology also lets scientists