Open AccessMercuric reductase genes ( merA ) and mercury resistance plasmids in H igh A rctic snow, freshwater and sea‐ice brine
Author(s) -
Møller Annette K.,
Barkay Tamar,
Hansen Martin A.,
Norman Anders,
Hansen Lars H.,
Sørensen Søren J.,
Boyd Eric S.,
Kroer Niels
Publication year - 2014
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12189
Subject(s) - biology , gammaproteobacteria , betaproteobacteria , alphaproteobacteria , deltaproteobacteria , psychrophile , plasmid , firmicutes , bacteroidetes , horizontal gene transfer , actinobacteria , phylogenetics , botany , genetics , bacteria , 16s ribosomal rna , gene
Bacterial reduction in H g 2+ to H g 0 , mediated by the mercuric reductase ( M er A ), is important in the biogeochemical cycling of H g in temperate environments. Little is known about the occurrence and diversity of merA in the A rctic. Seven merA determinants were identified among bacterial isolates from H igh A rctic snow, freshwater and sea‐ice brine. Three determinants in B acteriodetes , F irmicutes and A ctinobacteria showed < 92% (amino acid) sequence similarity to known merA , while one merA homologue in A lphaproteobacteria and 3 homologues from B etaproteobacteria and G ammaproteobacteria were > 99% similar to known merA 's. Phylogenetic analysis showed the B acteroidetes merA to be part of an early lineage in the mer phylogeny, whereas the B etaproteobacteria and G ammaproteobacteria merA appeared to have evolved recently. Several isolates, in which merA was not detected, were able to reduce H g 2+ , suggesting presence of unidentified merA genes. About 25% of the isolates contained plasmids, two of which encoded mer operons. One plasmid was a broad host‐range I nc P ‐α plasmid. No known incompatibility group could be assigned to the others. The presence of conjugative plasmids, and an incongruent distribution of merA within the taxonomic groups, suggests horizontal transfer of merA as a likely mechanism for H igh A rctic microbial communities to adapt to changing mercury concentration.