Mercury-responsive regulator

Huffman DL, Utschig LM, O Halloran TV (1997) Mercury-responsive gene regulation and mercury-199 as a probe of protein stmcture. Met Ions Biol Syst 34 503-526... 

Mercury Responsive Gene Regulation and Mercury-199 as a Probe of Protein Structure... 

Metal compounds, particularly compounds of the heavy metals, have a history of importance as antimicrobial agents. Because of regulations regarding economic poisons in the environment they are no longer widely used in this appHcation. Mercury, lead, cadmium, uranium, and other metals have been imphcated in cases of poisoning that resulted in government response. The metals whose compounds have been of primary interest as antimicrobials are mercury, silver, and copper. 

The European Union has been quite visible in recent years with such directives. RoHS (Restriction in the use of Hazardous Substances), WEEE (Waste of Electrical and Electronic Equipment), and REACH (Registration, Evaluation, Authorization, and Restriction of Chemical substances). RoHS places restrictions on use of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and some polybrominated diphenylethers. WEEE targets responsible recycling of electronic equipment. REACH is a new European Community Regulation on chemicals and their safe use... 

The promoters of ecCopA and YacK are apparently regulated by CueR. Both copper and silver are inducers, but not zinc or mercury. The loss of copper activation at both promoters in the cueR deletion strain can be rescued by complementing it with a plasmid carrying the gene. Interaction between CueR and the ecCopA promoter has been shown with a DNase I protection assay. It showed that CueR binds in vitro to a sequence with dyad symmetry within a 19-spacer sequence in the promoter (Stoyanov et al., 2001). CueR is thus the primary copper-responsive activator of the ecCopA copper efflux system of Es. coli. 

Several researchers have also suggested that bacteria mediate mercury reduction [54,55]. SicUiano et al. [56] recently examined the role of microbial reduction and oxidation processes in regulating DGM diel (over a 24h period) patterns in freshwater lakes. The authors demonstrate that photochemi-cally produced hydrogen peroxide regulates microbial oxidation processes and may account for the diel patterns observed in DGM data. Overall, the mechanisms responsible for mercury reduction and the relative contributions of biotic and abiotic processes are still unclear but solar radiation appears to be a common instigator of photo-reduction. 

New Hazardous Waste Regulations were introduced in July 2005 and under these regulations electric discharge lamps and tubes such as fluorescent, sodium, metal halide and mercury vapour are classified as hazardous waste. While each lamp only contains a very small amount of mercury, vast numbers are used and disposed of each year, resulting in a significant environmental threat. The environmentally responsible way to dispose of lamps and tubes is to recycle them and this process is now available through electrical wholesalers, as described in Chapter 1. 

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