Engineered Bacteria Based Biosensors for Monitoring Bioavailable Heavy Metals

This work presents an integrated analytical system based on immobilized engineered microorganisms and bioluminescence measurements for monitoring of bioavailable heavy metal ions (Cu being chosen as a model ion). A strain of microorganisms from Alcaligenes eutrophus (AE1239) was genetically engineered by inserting a luxCDABE operon from Vibrio fischeri under the control of a copper-induced promoter. As a result, copper ions induce bioluminescence, which is proportional to the concentration of the triggering ions, representing the basis of the design of the hereby described heavy metal biosensor. Microorganisms grown in two different media (Luria Broth and a modified mineral reconstitution medium/RM) were optimized and characterized in solution with regard to the influence of growth media and cell density in order to obtain optimal bioluminescent signals. Next, the microorganisms were immobilized in polymer matrices, compatible with fiber optics and were characterized with regard to sensitivity, selectivity, detection limit and storage stability. The lowest detection limit (1 μM) was achieved with microorganisms cultivated from glycerol stock solutions in the RM media and immobilized in a calcium alginate matrix.