Bioluminescence Biosensor for the Detection of Organomercury Contamination

Abstract

Abstract To selectively detect organomercurial compounds in the environment, in this study a bioluminescence biosensor for organomercurials was developed using a bacterial gene expression system for the mercury resistance determinant. merB 3 ‐Luciferase ( mer‐lux ) transcriptional fusion plasmids pHYΔ3Lux and pHY.Δ3Lux were constructed to evaluate the gene expression system with a new organomercury lyase gene merB 3 from Bacillus megaterium strain MB1, which is resistant to a broad spectrum of mercury compounds, and with its 3'end‐deleted defective merB3 , respectively. Another plasmid, pGR 1 A, encoding an operator/promoter sequence, merR 1 , merE , merT , merP and merA from the same bacterial strain was constructed and used as a transacting gene expression vector which combines the gene expression vector of mer‐lux transcriptional fusion plasmids in the same Escherichia coli cells. The transformants that carried a set of the two plasmids were used as biological sensors for the detection of organomercurials. Transformant ( E. coli DH5α/pHYB3Lux, pGR1A) is available to distinguish the organomercury from inorganic mercury, since inorganic mercurials can induce the bioluminescence of both the bacterial strain lines with pHYΔB3Lux and pHYB3Lux, whereas organomercurials can only induce the bioluminescence of the lines with pHYB3Lux. These experimental results showed that the transformant with a merB3 ‐defective fusion plasmid, and the gene expression vector responded to only mercury chloride. On the other hand, the transformant with an intact merB 3 fusion plasmid and the gene expression vector responded to mercury chloride and all organomercurials tested in the study. The sensor system responded to the existence of the phenyl mercury acetate of 50 nanomolar and was more sensitive than that of inorganic mercury (100 nanomolar). The result also indicated the capability of the system to detect bio‐affecting inorganic mercury from several hundred nanomolar to several ten micromolar.