title: Microbial DNA records historical delivery of anthropogenic mercury.
abstract: Mercury (Hg) is an anthropogenic pollutant that is toxic to wildlife and humans, but the response of remote ecosystems to globally distributed Hg is elusive. Here, we use DNA extracted from a dated sediment core to infer the response of microbes to historical Hg delivery. We observe a significant association between the mercuric reductase gene (merA) phylogeny and the timing of Hg deposition. Using relaxed molecular clock models, we show a significant increase in the scaled effective population size of the merA gene beginning ~200 years ago, coinciding with the Industrial Revolution and a coincident strong signal for positive selection acting on residues in the terminal region of the mercuric reductase. This rapid evolutionary response of microbes to changes in the delivery of anthropogenic Hg indicates that microbial genomes record ecosystem response to pollutant deposition in remote regions.
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Alexandre J
authors.initials: AJ
authors.lastname: Poulain
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.|Department of Mathematics and Statistics, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Aris-Brosou
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jules M
authors.initials: JM
authors.lastname: Blais
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Brazeau
authors.affiliation: Cooperative Freshwater Ecology Unit, Vale Living with Lakes Centre, Laurentian University, Sudbury, Ontario, Canada.
authors.forename: Wendel Bill
authors.initials: WB
authors.lastname: Keller
authors.affiliation: Dorset Environmental Science Centre, Ontario Ministry of the Environment and Climate Change, Dorset, Ontario, Canada.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Paterson
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics*; D017753:Ecosystem; D004785:Environmental Pollutants / Q000032:analysis* / Q000378:metabolism; D004787:Environmental Pollution / Q000266:history; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D008628:Mercury / Q000032:analysis* / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004785:Environmental Pollutants; D010088:Oxidoreductases; C021551:mercuric reductase; D008628:Mercury