Whole cell- and protein-based biosensors for the detection of bioavailableheavy metals in environmental samples

The principal goal of this work was to establish the feasibility of two bio sensor technologies with enhanced specificity and selectivity for the detec tion of several bioavailable heavy metals in environmental samples. Two par allel strategies have been followed. The first approach was to construct wh ole cell bacterial biosensors that emit a bioluminescent or fluorescent sig nal in the presence of a biologically available heavy metal. The molecular basis of sigma-54 promoters as sensing elements of environmental pollutants has been determined and a number of metal-induced promoter regions have be en identified, sequenced and cloned as promoter cassettes. The specificity of the promoter cassettes has been determined using luxCDABE reporter syste ms. Whole cell-biosensors containing metal-induced lux reporter systems hav e been incorporated into different matrices for their later immobilisation on optic fibres and characterised in terms of their sensitivity and storage capacity. The second type of censors was based on the direct interaction b etween metal-binding proteins and heavy metal ions. In this case, the capac itance changes of the proteins, such as synechoccocal metallothionein (as a GST-SmtA fusion protein) and the mercury regulatory protein, MerR, were de tected in the presence of femtomolar to millimolar metal ion concentrations . (C) 1999 Elsevier Science B.V. All rights reserved.