title: Involvement of the smeAB multidrug efflux pump in resistance to plant antimicrobials and contribution to nodulation competitiveness in Sinorhizobium meliloti.
abstract: The contributions of multicomponent-type multidrug efflux pumps to antimicrobial resistance and nodulation ability in Sinorhizobium meliloti were comprehensively analyzed. Computational searches identified genes in the S. meliloti strain 1021 genome encoding 1 pump from the ATP-binding cassette family, 3 pumps from the major facilitator superfamily, and 10 pumps from the resistance-nodulation-cell division family, and subsequently, these genes were deleted either individually or simultaneously. Antimicrobial susceptibility tests demonstrated that deletion of the smeAB pump genes resulted in increased susceptibility to a range of antibiotics, dyes, detergents, and plant-derived compounds and, further, that specific deletion of the smeCD or smeEF genes in a ΔsmeAB background caused a further increase in susceptibility to certain antibiotics. Competitive nodulation experiments revealed that the smeAB mutant was defective in competing with the wild-type strain for nodulation. The introduction of a plasmid carrying smeAB into the smeAB mutant restored antimicrobial resistance and nodulation competitiveness. These findings suggest that the SmeAB pump, which is a major multidrug efflux system of S. meliloti, plays an important role in nodulation competitiveness by mediating resistance toward antimicrobial compounds produced by the host plant.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan. eda@ige.tohoku.ac.jp
authors.forename: Shima
authors.initials: S
authors.lastname: Eda
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Mitsui
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D017353:Gene Deletion; D019450:Genes, MDR; D005816:Genetic Complementation Test; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D026901:Membrane Transport Proteins