title: Horizontal spread of mer operons among gram-positive bacteria in natural environments.
abstract: Horizontal dissemination of the genes responsible for resistance to toxic pollutants may play a key role in the adaptation of bacterial populations to environmental contaminants. However, the frequency and extent of gene dissemination in natural environments is not known. A natural horizontal spread of two distinct mercury resistance (mer) operon variants, which occurred amongst diverse Bacillus and related species over wide geographical areas, is reported. One mer variant encodes a mercuric reductase with a single N-terminal domain, whilst the other encodes a reductase with a duplicated N-terminal domain. The strains containing the former mer operon types are sensitive to organomercurials, and are most common in the terrestrial mercury-resistant Bacillus populations studied in this work. The strains containing the latter operon types are resistant to organomercurials, and dominate in a Minamata Bay mercury-resistant Bacillus population, previously described in the literature. At least three distinct transposons (related to a class II vancomycin-resistance transposon, Tn1546, from a clinical Enterococcus strain) and conjugative plasmids are implicated as mediators of the spread of these mer operons.
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: E S
authors.initials: ES
authors.lastname: Bogdanova
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: I A
authors.initials: IA
authors.lastname: Bass
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: L S
authors.initials: LS
authors.lastname: Minakhin
authors.affiliation: Center of Microbial Ecology, Michigan State University, East Lansing, MI, USA.|Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: M A
authors.initials: MA
authors.lastname: Petrova
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: S Z
authors.initials: SZ
authors.lastname: Mindlin
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: A A
authors.initials: AA
authors.lastname: Volodin
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: E S
authors.initials: ES
authors.lastname: Kalyaeva
authors.affiliation: Center of Microbial Ecology, Michigan State University, East Lansing, MI, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Tiedje
authors.affiliation: School of Biological Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: J L
authors.initials: JL
authors.lastname: Hobman
authors.affiliation: School of Biological Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: N L
authors.initials: NL
authors.lastname: Brown
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
authors.forename: V G
authors.initials: VG
authors.lastname: Nikiforov
mesh_terms: D001407:Bacillus / Q000187:drug effects / Q000235:genetics*; D004251:DNA Transposable Elements; D004352:Drug Resistance, Microbial / Q000235:genetics*; D014644:Genetic Variation; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000235:genetics*; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D009941:Organomercury Compounds / Q000494:pharmacology; D010088:Oxidoreductases / Q000235:genetics; D010802:Phylogeny; D010957:Plasmids; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004251:DNA Transposable Elements; D009941:Organomercury Compounds; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C021551:mercuric reductase; D008628:Mercury