[Construction of Hg(2+)-induced luminescent reporter gene system and its application to detect mercury in red soil]

A luminescent reporter gene system was constructed by fusing the mercury-inducible promoter, P(merT), and its regulatory gene, merR with a promoterless reporter gene EGFP. A stable whole-cell reporter was created by mini-Tn5 and introducing the merR-egfp system cassette into the chromosome of Pseudomonas putida strain, then applied it for mercury detection in the red soil of Jiangxi province, the fluorescence density of the sensor strain was confirmed in soil extraction and fluorescence intensity was quantified by flow cytometry. The results showed positive correlation with the mercury pollutant in the concentration range of 0.04-50 mg x kg(-1). The background heavy metal irons such as Cr2+, Zn2+, Co2+, Cu2+, Pb2+, Ag+ at certain level did not interfere with the measurement. The key factor for detecting the fluorescence density was the induction time and the optimal temperature for EGFP expression was 30-35 degrees C. Spiked with 0.1 mg x kg(-1) Hg2+ and after 15 and 30 days incubation, red soil samples were extracted and evaluated water soluble, bioavailable, organic matter bound and residual fractions of mercury by both sensor strain and analytical way. The sensor strain appeared to have a detection range similar to that of atomic absorption spectroscopy (AAS) method and the effective detection ratio was 35%-64%.