Biological techniques for measuring organic and metal contaminants in environmental samples

Traditional approaches used to measure organic and inorganic contaminants in environmental samples include gas chromatography (GC), or high performance liquid chromatography (HPLC) for organics, and atomic absorption (AA) or inductively coupled plasma spectroscopy (ICP) for metals. While these analytical techniques are well characterized and have good detection limits, the cost of purchasing the analytical equipment is high, and the training necessary to run these instruments is extensive. In fact, in many instances it is more cost effective to send samples to a commercial analytical laboratory for analysis. As a result of the time and cost constraints imposed by these traditional approaches, alternative techniques, based on biological systems, have been developed for detection and quantitation of environmental contaminants. These techniques are sensitive, rapid, frequently less expensive, and in some cases can be implemented directly in the field. The application of two such techniques for detection and measurement of environmental contaminants are discussed in this chapter; immunoassays and bioreporter systems. These techniques are quite different and the measurements that they provide have different meanings. For example, bioreporter systems, also called biosensors, are whole bacterial cells and require that the contaminant or analyte enter the cell before eliciting a response. These bioreporter systems can be designed to study physiological responses to environmental stress (e.g., the presence of a contaminant) or they can be quantitative by designing them to synthesize a specific gene product in response to the presence of a contaminant. Immunoassays, on the other hand, use biological products to detect and quantitate chemicals, but they are not living systems. While this difference may not seem profound, it should be noted that the use of bioreporter organisms allows for the determination of “bioavailable chemical” or the amount of chemical that can be taken up by the microbial cell. It is this quantity of chemical, one which is difficult to measure, that is becoming increasingly important in evaluation of hazardous waste sites (Natl. Res. Counc., 1993). This is because while it is costly and difficult to completely restore a contaminated site, it may be more feasible to reduce the amount of contamination so that very little bioavailable material remains.