Mosher JJ, Vishnivetskaya TA, Elias DA, Podar M, Brooks SC, Brown SD, Brandt CC, Palumbo AV
Microbial communities were examined in surface stream sediments at 5 contaminated sites and 1 control site near Oak Ridge, TN, USA, to identify bacteria that could be contributing to mercury (Hg) methylation. The phylogenetic composition of the sediment bacterial community was examined over 3 quarterly sampling periods (36 samples) using 16S rRNA gene pyrosequencing. Only 3064 sequences (0.85% of the total community) were identified as Deltaproteobacteria, the only group known to methylate Hg, using the Ribosomal Database Project classifier at the 99% confidence threshold. Constrained ordination techniques indicated statistically significant positive linear correlations between Desulfobulbus spp., Desulfonema spp. and Desulfobacca spp. and methyl-Hg concentrations at the Hg-contaminated sites. In contrast, the distribution of organisms related to Byssovorax spp. was significantly correlated to inorganic carbon, nitrate and uranium concentrations but not to Hg or methyl-Hg. Overall, the abundance and richness of Deltaproteobacteria sequences were higher in uncontaminated sediments, while the majority of the members present at the contaminated sites were either known potential metal-reducers/methylators or metal tolerant species. Given the abundance relative to other known Hg methylators and the association with methyl-Hg, Desulfobulbus spp. is considered a prime candidate for involvement in Hg methylation in these streams.
Mosher JJ, Vishnivetskaya TA, Elias DA, Podar M, Brooks SC, Brown SD, Brandt CC, Palumbo AV. 2012. Characterization of the Deltaproteobacteria in contaminated and uncontaminated stream sediments and identification of potential mercury methylators. Aquatic Microbial Ecology 66:271–282.