GENETICALLY ENGINEERED MICROORGANISMS FOR POLLUTION MONITORING

At the heart of every biosensor is a biological entity, the purpose of which is to react with the target analyte(s) and generate a readily quantifiable signal. Traditional biosensors are based on the unique specificity of enzymes to their substrates, antibodies to antigens or that of nucleic acids to their complementary sequences. In recent years we have promoted the use of a different concept, that of whole cell biosensors: natural or genetically engineered live cells that respond to pre-determined classes of chemicals. While some of the specificity characterizing molecule-based biosensors may be lost, it is more than compensated for by the fact that by using live cells we are able to detect, by very simple means, very complex series of reactions that can exist only in an intact, functioning cell. Only a sensor of this type can report on the "well being" of a system, on the toxicity of a sample, the genotoxicity of a chemical or the bioavailability of a pollutant. No molecular recognition or chemical analysis can provide this type of information. In order to turn such sensor cells into "real" biosensors, they need to be immobilized onto a solid platform and coupled into a signal transduction apparatus. Several avenues taken to accomplish this goal are described, including encapsulation in sol-gel, immobilization at the tips of optic fibers and integration into silicon chips.