Plasmid mediation of mercury volatilization and methylation by estuarine bacteria (Reprinted from Developments in Industrial Microbiology, vol 20, pg275-284, 1979)

The efficiency of microbial volatilization of mercury was examined using ba cterial strains isolated from Chesapeake Bay, a major estuary of the easter n seaboard of the United States, and one strain isolated from the Cayman Tr ench, a deep ocean site. Volatilization of mercury was studied under both a erobic and anaerobic conditions. The mechanism of mercury volatilization wa s determined to be plasmid mediated in two of the strains tested, but appea red to be chromosomally mediated in one strain of Pseudomonas fluorescens. The percent of mercury volatilized under aerobic conditions from media cont aining ill mg HgCl2/liter ranged from 21.5-87.2% within 24 h. Incubation un der anaerobic conditions resulted in 12.7-78.1% volatilization of the mercu ry. Mercuric reductases associated with the plasmids were shown to be respo nsible for volatilization of mercury. Aerobic volatilization of mercury was observed to be more efficient than anaerobic volatilization. Furthermore, methylation of mercury was found to be a phenomenon separate from volatiliz ation, with only two of the bacterial strains proving capable of producing methylmercury under either aerobic or anaerobic conditions, it is concluded that bacteria can mobilize mercury in the marine environment and may be po tential agents for recycling mercury from mercury-laden wastes.