Interplay between the efflux pump and the outer membrane permeability barrier in fluorescent dye accumulation in Pseudomonas aeruginosa.
Pseudomonas aeruginosa encodes three types of xenobiotic efflux pumps, MexAB-OprM, MexCD-OprJ, and MexEF-OprN, which are regulated by the nalB, nfxB, and nfxC genes, respectively, and their high expression renders the cells resistant to multiple species of antibiotics. We evaluated the role of the outer membrane permeability barrier and the efflux pump in lowering the intracellular concentration of fluorescent probes. The wild-type, nalB, nfxB, and nfxC strains with an intact outer membrane showed equally high capability in draining out intracellular fluorescent dye, 2-(4-dimethylaminostyryl)-1-ethylpyridinium and ethidium bromide. When the outer membrane barrier was dismantled by the EDTA treatment, wild-type, nfxC, nfxB, and nalB strains showed significantly different levels of dye accumulation. The polymyxin B-treated cells showed an even more pronounced difference in dye accumulation among the nfxC, nfxB, and nalB mutants. We concluded from these results that the xenobiotic extrusion pumps interplay with the outer membrane permeability barrier in lowering the intracellular substrate concentration. Among three extrusion pumps in P. aeruginosa, MexAB-OprM was the most efficient, followed by MexCD-OprJ and MexEF-OprN pumps for the fluorescent dye extrusion.
Germ
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School of Medicine, Tokai University, Isehara, 259-1193, Japan.
Yoshihara
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Yoneyama
H
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Nakae
T
T
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018432:Drug Resistance, Multiple; D004492:Edetic Acid / Q000494:pharmacology; D004996:Ethidium / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005798:Genes, Bacterial; D009154:Mutation; D011112:Polymyxin B / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000493:pharmacokinetics; D014157:Transcription Factors; D015262:Xenobiotics / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; C077901:NfxB protein, Pseudomonas aeruginosa; D011726:Pyridinium Compounds; D014157:Transcription Factors; D015262:Xenobiotics; C025042:2-(dimethylaminostyryl)-1-ethylpyridinium; D004492:Edetic Acid; D004996:Ethidium; D011112:Polymyxin B