A whole-cell bacterial biosensor was developed for detecting low concentrations of organomercurials in the environment. The sensor plasmid for bioavailable Hg2+ (pHYRnLux) was constructed by fusing the mercury inducible promoter and its regulatory gene, merR, from Pseudomonas strain K-62 with the reporter genes luxAB from Vibrio harveyi. Another plasmid carrying the organomercurial lyase gene, merB3, from Bacillus megaterium MB1 was also constructed and transformed into Escherichia coli DH5 α with pHYRnLux. The resulting bacterial biosensor carrying these two plasmids responded to a various organomercurials including methylmercury chloride (MMC), ethylmercury chloride (EMC), phenylmercury acetate (PMA) and thimerosal. Under a 10-minute exposure condition, the lowest detectable concentrations of MMC and PMA were 3nM and 30nM, respectively. However, increasing the exposure time to 60 minutes allowed the detection of 300pM MMC and 3nM PMA. Thus, the constructed bacterial biosensor allows the detection of a various organomercurials from the picomolar level to the nanomolar level within 60 minutes and may be useful for monitoring bioavailable organomercurials in environmental samples.
