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

• Published in: FEMS Microbiology Ecology
• Main Authors: Møller, Annette K., Barkay, Tamar, Abu Al-Soud, Waleed Mohamad Abdel F, Sørensen, Søren J., Skov, Henrik, Kroer, Niels A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: mercury concentration; bacterial mercury; Arctic; Sea ice
• Online Access: https://pure.au.dk/portal/da/publications/diversity-and-characterization-of-mercuryresistant-bacteria-in-snow-freshwater-and-seaice-brine-from-the-high-artic(f9bfe56f-38cc-4a38-a88c-f3f49332cdf5).html; https://doi.org/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 9.4105, 5105 and 0.9–3.1103 cells mL1 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 o2% 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.