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Organomercurial resistance determinants in Pseudomonas K-62 are present on two plasmids

M Kiyono1, T Omura, H Fujimori

  • 1Faculty of Pharmaceutical Sciences, Setsunan University, Osaka, Japan.

Archives of Microbiology
|April 1, 1995
PubMed

Insights

Pseudomonas strain K-62

Area of Science:

  • Microbiology
  • Molecular Biology
  • Environmental Science

Background:

  • Pseudomonas strain K-62 harbors six plasmids, influencing its characteristics.
  • Mercury resistance in bacteria is often plasmid-mediated.
  • Understanding the genetic basis of mercury resistance is crucial for environmental remediation.

Purpose of the Study:

  • To elucidate the plasmid-based genetic determinants of organomercurial resistance in Pseudomonas strain K-62.
  • To identify the specific plasmids and genes responsible for mercury volatilization and resistance.
  • To characterize the function of cloned mercury resistance genes.

Main Methods:

  • Plasmid curing experiments to generate mutant strains.
  • Mercury volatilization assays.
  • Southern hybridization using mer gene probes (merA, merB, merR).
  • Cloning of mer gene fragments into Escherichia coli for functional expression.

Main Results:

  • Loss of the 26-kb plasmid increased sensitivity to mercurials but retained volatilization.
  • Loss of both 26-kb and 68-kb plasmids abolished mercury volatilization and reduced resistance.
  • The 26-kb plasmid hybridized with merA, merB, and merR probes.
  • Cloned fragments from the 26-kb plasmid conferred inducible broad-spectrum resistance or constitutive hypersensitivity to phenylmercury.

Conclusions:

  • Organomercurial resistance in Pseudomonas K-62 is plasmid-based, requiring both 26-kb and 68-kb plasmids for full expression.
  • The 26-kb plasmid carries essential mer genes (merA, merB, merR).
  • Two distinct organomercurial lyases are likely transcribed from separate operator-promoters.

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