Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic

• Published in: FEMS microbiology ecology Vol. 75; no. 3; pp. 390 - 401
• Main Authors: Møller, Annette K, Barkay, Tamar, Al-Soud, Waleed Abu, Sørensen, Søren J, Skov, Henrik, Kroer, Niels
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2011; Blackwell; Oxford University Press
• Subjects: Actinobacteria; Animal, plant and microbial ecology; Arctic bacteria; Arctic region; Arctic Regions; atmospheric deposition; Bacteria; Bacteria - classification; Bacteria - drug effects; Bacteria - genetics; Bacteria - growth & development; Bacteria - metabolism; bacterial mercury reduction; Bacteriodetes; Bacteriology; Biodiversity; Biological and medical sciences; Brines; Drug Resistance, Bacterial; Ecology; Firmicutes; food chain; Fresh water; Fresh Water - microbiology; freshwater; Freshwater ice; Fundamental and applied biological sciences. Psychology; gamma-Proteobacteria; Ice Cover - microbiology; latitude; Marine; Mercury; Mercury - metabolism; Mercury - pharmacology; mercury concentration; mercury resistance; methylation; Methylmercury; methylmercury compounds; Microbial ecology; Microbial Sensitivity Tests; Microbiology; Miscellaneous; Molecular Sequence Data; Oxidation-Reduction; phylogeny; risk; RNA, Ribosomal, 16S - genetics; Sea ice; Snow; Snow - microbiology; temperature; Water Pollutants, Chemical - metabolism; Water Pollutants, Chemical - pharmacology; Arctic Region; Arctic Regions; Arctic region; PN, Arctic; mercury concentration; bacterial mercury reduction; mercury resistance; Arctic bacteria; Snow; Diversity; Fresh water; Brine; Environmental factor; Climatic zone; Heavy metal; Infection; Characterization; Freshwater environment; Resistance; Aquatic environment; Pollutant; Sensitivity resistance; Bacteriosis; Bacteria; Polar region; Atmospheric precipitation; Mercury; Sea ice
• ISSN: 0168-6496; 1574-6941; 1574-6941
• DOI: 10.1111/j.1574-6941.2010.01016.x

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 × 10⁵, 5 × 10⁵ and 0.9-3.1 × 10³ 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.