Research Product

An investigation was conducted on the Hg2+ resistance mechanism of four freshwater and four coastal marine bacteria that did not hybridize with a mer operonic probe (T. Barkay, C. Liebert, and M. Gillman, Appl. Environ. Microbiol. 55, 1196, 1989). Inducible Hg2+ volatilization was demonstrated for all eight organisms and NADPH-dependent mercuric reductase activities were detected in crude cell extracts of six of the strains. Hybridization with a mer A probe, the gene encoding the mercuric reductase polypeptide, at a stringency permitting hybrid formation between evolutionary distant merA genes (as exists between gram positive and negative bacteria) detected merA sequences in the genomes of all tested strains. Because these strains represented random selections of bacteria from three aquatic environments, it is concluded that merA encodes a common molecular mechanism for Hg2+ resistance and volatilization in aerobic heterotrophic aquatic communities.