Environmental significance of the potential for mer(Tn21)-mediated reduction of Hg2+ to Hg0 in natural waters.
The role of mer(Tn21) in the adaptation of aquatic microbial communities to Hg2+ was investigated. Elemental mercury was the sole product of Hg2+ volatilization by freshwater and saline water microbial communities. Bacterial activity was responsible for biotransformation because most microeucaryotes did not survive the exposure conditions, and removal of larger microbes (greater than 1 micromole) from adapted communities did not significantly (P greater than 0.01) reduce Hg2+ volatilization rates. DNA sequences homologous to mer(Tn21) were found in 50% of Hg2+-resistant bacterial strains representing two freshwater communities, but in only 12% of strains representing two saline communities (the difference was highly significant; P less than 0.001). Thus, mer(Tn21) played a significant role in Hg2+ resistance among strains isolated from fresh waters, in which microbial activity had a limited role in Hg2+ volatilization. In saline water environments in which microbially mediated volatilization was the major mechanism of Hg2+ loss, other bacterial genes coded for this biotransformation.
Barkay
T
T
Microbial Ecology and Biotechnology Branch, Environmental Research Laboratory, U.S. Environmental Protection Agency, Gulf Breeze, Florida 32561.
Liebert
C
C
Gillman
M
M
D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D001711:Biotransformation; D004251:DNA Transposable Elements; D004352:Drug Resistance, Microbial; D056890:Eukaryota / Q000187:drug effects / Q000378:metabolism; D005618:Fresh Water; D005798:Genes, Bacterial; D008628:Mercury / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D012623:Seawater; D014835:Volatilization; D014871:Water Microbiology; D014874:Water Pollutants, Chemical
D004251:DNA Transposable Elements; D014874:Water Pollutants, Chemical; D008628:Mercury