title: Mercury resistance transposons in Bacilli strains from different geographical regions.
abstract: A total of 65 spore-forming mercury-resistant bacteria were isolated from natural environments worldwide in order to understand the acquisition of additional genes by and dissemination of mercury resistance transposons across related Bacilli genera by horizontal gene movement. PCR amplification using a single primer complementary to the inverted repeat sequence of TnMERI1-like transposons showed that 12 of 65 isolates had a transposon-like structure. There were four types of amplified fragments: Tn5084, Tn5085, Tn(d)MER3 (a newly identified deleted transposon-like fragment) and Tn6294 (a newly identified transposon). Tn(d)MER3 is a 3.5-kb sequence that carries a merRETPA operon with no merB or transposase genes. It is related to the mer operon of Bacillus licheniformis strain FA6-12 from Russia. DNA homology analysis shows that Tn6294 is an 8.5-kb sequence that is possibly derived from Tn(d)MER3 by integration of a TnMERI1-type transposase and resolvase genes and in addition the merR2 and merB1 genes. Bacteria harboring Tn6294 exhibited broad-spectrum mercury resistance to organomercurial compounds, although Tn6294 had only merB1 and did not have the merB2 and merB3 sequences for organomercurial lyases found in Tn5084 of B. cereus strain RC607. Strains with Tn6294 encode mercuric reductase (MerA) of less than 600 amino acids in length with a single N-terminal mercury-binding domain, whereas MerA encoded by strains MB1 and RC607 has two tandem domains. Thus, Tn(d)MER3 and Tn6294 are shorter prototypes for TnMERI1-like transposons. Identification of Tn6294 in Bacillus sp. from Taiwan and in Paenibacillus sp. from Antarctica indicates the wide horizontal dissemination of TnMERI1-like transposons across bacterial species and geographical barriers.
authors.affiliation: Department of Civil and Environmental Engineering, Kinki University, Higashiosaka, Osaka 577-8502, Japan kmatsui@civileng.kindai.ac.jp.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Matsui
authors.affiliation: Department of Civil and Environmental Engineering, Kinki University, Higashiosaka, Osaka 577-8502, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshinami
authors.affiliation: Tohoku Afforestation and Environmental Protection Co, Sendai, Miyagi 980-0014, Japan Laboratory of Environmental Biotechnology, Tohoku Gakuin University, Tagajo, Miyagi 985-8537, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Narita
authors.affiliation: Laboratory of Environmental Biotechnology, Tohoku Gakuin University, Tagajo, Miyagi 985-8537, Japan Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Mei-Fang
authors.initials: MF
authors.lastname: Chien
authors.affiliation: Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612 USA.
authors.forename: Le T
authors.initials: le T
authors.lastname: Phung
authors.affiliation: Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612 USA.
authors.forename: Simon
authors.initials: S
authors.lastname: Silver
authors.affiliation: Laboratory of Environmental Biotechnology, Tohoku Gakuin University, Tagajo, Miyagi 985-8537, Japan.
authors.forename: Ginro
authors.initials: G
authors.lastname: Endo
mesh_terms: D001407:Bacillus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D022761:Gene Transfer, Horizontal / Q000502:physiology; D005843:Geography; D008190:Lyases / Q000235:genetics*; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D017422:Sequence Analysis, DNA; D019895:Transposases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C051124:MerR protein, Bacteria; D010088:Oxidoreductases; C021551:mercuric reductase; D019895:Transposases; D008190:Lyases; C097247:MerB protein, Bacteria; D008628:Mercury
keywords: Bacilli; broad-spectrum mercury resistance; horizontal gene transfer; mer operon; worldwide gene dissemination