title: mexEF-oprN multidrug efflux operon of Pseudomonas aeruginosa: regulation by the MexT activator in response to nitrosative stress and chloramphenicol.
abstract: A null mutation in the mexS gene of Pseudomonas aeruginosa yielded an increased level of expression of a 3-gene operon containing a gene, xenB, whose product is highly homologous to a xenobiotic reductase in Pseudomonas fluorescens shown previously to remove nitro groups from trinitrotoluene and nitroglycerin (D. S. Blehert, B. G. Fox, and G. H. Chambliss, J. Bacteriol. 181:6254, 1999). This expression, which paralleled an increase in mexEF-oprN expression in the same mutant, was, like mexEF-oprN, dependent on the MexT LysR family positive regulator previously implicated in mexEF-oprN expression. As nitration is a well-known result of nitrosative stress, a role for xenB (and the coregulated mexEF-oprN) in a nitrosative stress response was hypothesized and tested. Using s-nitrosoglutathione (GSNO) as a source of nitrosative stress, the expression of xenB and mexEF-oprN was shown to be GSNO inducible, although in the case of xenB, this was seen only for a mutant lacking MexEF-OprN. In both instances, this GSNO-inducible expression was dependent upon MexT. Chloramphenicol, a nitroaromatic antimicrobial that is a substrate for MexEF-OprN, was shown to induce mexEF-oprN but not xenB, again dependent upon the MexT regulator, possibly because it resembles a nitrosated nitrosative stress product accommodated by MexEF-OprN.
authors.affiliation: Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada.
authors.forename: Hossam
authors.initials: H
authors.lastname: Fetar
authors.forename: Christie
authors.initials: C
authors.lastname: Gilmour
authors.forename: Rachael
authors.initials: R
authors.lastname: Klinoski
authors.forename: Denis M
authors.initials: DM
authors.lastname: Daigle
authors.forename: Charles R
authors.initials: CR
authors.lastname: Dean
authors.forename: Keith
authors.initials: K
authors.lastname: Poole
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002701:Chloramphenicol / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000235:genetics; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D018869:Heat-Shock Response; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009876:Operon / Q000187:drug effects*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D026422:S-Nitrosoglutathione / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D005420:Flavoproteins; D026901:Membrane Transport Proteins; D020030:Nitric Oxide Donors; C105708:OprN protein, Pseudomonas aeruginosa; C122135:XenB protein, Pseudomonas; D026422:S-Nitrosoglutathione; D002701:Chloramphenicol; D010088:Oxidoreductases