Detection of bioavailable heavy metals in EILATox-Oregon samples using whole-cell luminescent bacterial sensors in suspension or immobilized onto fibre-optic tips

At the EILATox-Oregon Workshop, nine luminescent whole-cell bacterial sensors were used for the determination of bioavailable metals in blind samples (17 synthetic and 3 environmental). A non-inducible luminescent control strain was used to determine sample matrix effects and bacterial toxicity. Whole-cell bacterial sensors capable of determining arsenic, inorganic mercury and its organic derivatives, cadmium, lead or copper were used in suspensions and a bacterial sensor for the detection of inorganic mercury was immobilized onto fibre-optic tips using calcium alginate. Bioavailable amounts of metals were estimated using calibration plots, that were constructed to determine the range of metals giving rise to a linear relationship between luminescence and the amount of metals present in the standard solutions. EILATox-Oregon sample 5, which contained 74 mg l^-1 of Hg, gave a significant response with both formats of the mercury sensor. The bioavailable amounts of mercury according to the measurement of bacterial sensor in suspension and immobilized onto a fibre-optic tip were 76 and 93 mg l^-1, respectively. The bacterial sensor for arsenic and copper showed a response with sample 6 (58 mg l^-1 of As) and sample 8 (400 mg l^-1 of metham sodium), respectively. This study showed that the bacterial sensors in suspension or immobilized onto optical fibres are capable of quantifying bioavailable metals from unknown samples. The measurement protocol of bacterial sensors is simple and possible to perform in the field. Moreover, the samples do not need any pretreatment before analysis. Construction and characterization of the strain for the detection of bioavailable copper are described.