Sensing Superfund Chemicals with Recombinant Systems

There is an on-going need for simple analytical methods capable of detecting either class-selectively or compound-selectively toxic substances in the environment and in biological samples.  Exciting emerging technologies have allowed for the design and development of a variety of new methods, including new cell- and protein-based biosensors.  Despite the fact that some of these methods have already found applications in the environmental monitoring of a number of pollutants, the need for sensing systems for polyhalogenated organic pollutants is still pressing.  Among this class of compounds, polychlorinated biphenyls (PCBs) are the ones that have been better characterized and studied, and are classified as Superfund chemicals.  A trademark of all polyhalogenated organics is that they are persistent in nature and require extensive sample pretreatment before they can be detected. 

Rather recently, we demonstrated that we can employ molecular tools in the highly sensitive and direct detection of chlorinated organics.  These molecular biosensors are based on bacteria engineered to harbor a plasmid containing the genes encoding for the proteins involved in the catabolic pathways of Superfund chemicals coupled to those of a signal-producing reporter protein.  The presence of such chemicals triggers the expression of the reporter protein in a manner that is directly proportional to the levels of these chemicals.  The detection of these chemicals is sensitive and class-selective, allowing for the determination of these compounds in biological and environmental samples.  The success in the design and development of these biosensors has led us to the incorporation of the regulatory protein of bacterial resistance operons as the recognition element in molecular biosensing systems.  Specifically, we are redesigning these regulatory proteins employing genetic engineering tools so that they can bind selectively to target analytes.  These redesigned proteins should be able act as molecular switches to detect the presence of the target compounds in samples.  In addition, the newly developed biosensing systems are miniaturized for in situ detection and field studies.