title: Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic.
abstract: It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but <2% in freshwater and brine. The resistant bacteria belonged to the Alpha-, Beta- and Gammaproteobacteria, Firmicutes, Actinobacteria, and Bacteriodetes. Resistance levels of most isolates were not temperature dependent. Of the resistant isolates, 25% reduced Hg(II) to Hg(0). No relation between resistance level, ability to reduce Hg(II) and phylogenetic group was observed. An estimation of the potential bacterial reduction of Hg(II) in snow suggested that it was important in the deeper snow layers where light attenuation inhibited photoreduction. Thus, by reducing Hg(II) to Hg(0), mercury-resistant bacteria may limit the supply of substrate for methylation processes and, hence, contribute to lowering the risk that methylmercury is being incorporated into the Arctic food chains.
authors.affiliation: National Environmental Research Institute, Aarhus University, Roskilde, Denmark.
authors.forename: Annette K
authors.initials: AK
authors.lastname: Møller
authors.forename: Tamar
authors.initials: T
authors.lastname: Barkay
authors.forename: Waleed
authors.initials: W
authors.lastname: Abu Al-Soud
authors.forename: Søren J
authors.initials: SJ
authors.lastname: Sørensen
authors.forename: Henrik
authors.initials: H
authors.lastname: Skov
authors.forename: Niels
authors.initials: N
authors.lastname: Kroer
mesh_terms: D001110:Arctic Regions; D001419:Bacteria / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D044822:Biodiversity; D024881:Drug Resistance, Bacterial; D005618:Fresh Water / Q000382:microbiology*; D046448:Ice Cover / Q000382:microbiology*; D008628:Mercury / Q000378:metabolism / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012914:Snow / Q000382:microbiology*; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000494:pharmacology
chemical_list: D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D008628:Mercury