title: Identification of Tet45, a tetracycline efflux pump, from a poultry-litter-exposed soil isolate and persistence of tet(45) in the soil.
abstract: OBJECTIVE
  To characterize a tetracycline resistance (Tc(R)) determinant, closely related to the TetL efflux pump, in a Bhargavaea cecembensis strain previously isolated from a poultry-litter-impacted soil.
  
  
  METHODS
  Genomic DNA of B. cecembensis DMV42A was shotgun cloned and expressed in Escherichia coli. Antimicrobial susceptibility testing and a [(3)H]tetracycline uptake assay were used to confirm the function of the target gene. Transferability of the gene was examined using filter matings and confirmed by PCR and sequencing. Real-time quantitative PCR was performed on soil metagenomic DNA to evaluate the prevalence of the gene in the soil from which B. cecembensis DMV42A was isolated and in more pristine local soils.
  
  
  RESULTS
  The Tc(R) determinant from B. cecembensis DMV42A, designated Tet45, was identified as a tetracycline efflux pump sharing 78% amino acid identity with certain TetL proteins. In B. cecembensis DMV42A, tet(45) was adjacent to truncated and non-functional arsenic resistance genes with high sequence similarities to genes from staphylococcal plasmids. After filter matings, the tet(45) gene could be found in E. coli transconjugants, although the transfer mechanism was unknown. Tet45 homologues are also present in the genomes of several Bacillus cereus strains and a Bacillus thuringiensis strain. tet(45) was detected in the poultry-litter-impacted soil, and persisted at a similar level 2 years after removal of the chicken waste, although it was not detected in several more pristine soils.
  
  
  CONCLUSIONS
  Tet45 is a tetracycline efflux pump closely related to TetL. Horizontal gene transfer may have contributed to the dissemination and persistence of tet(45) in a poultry-litter-impacted soil.
authors.affiliation: Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD 21218, USA. you.yaqi@jhu.edu
authors.forename: Yaqi
authors.initials: Y
authors.lastname: You
authors.forename: Markus
authors.initials: M
authors.lastname: Hilpert
authors.forename: Mandy J
authors.initials: MJ
authors.lastname: Ward
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D022761:Gene Transfer, Horizontal; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D058641:Planococcaceae / Q000235:genetics* / Q000302:isolation & purification; D011200:Poultry; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013752:Tetracycline / Q000378:metabolism; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; D013752:Tetracycline
keywords: Tn5397-like element; efflux pump; poultry farm soil; tetracycline resistance