Two routes of MexS‐MexT‐mediated regulation of MexEF‐OprN and MexAB‐OprM efflux pump expression in Pseudomonas aeruginosa. (15th April 2013)

• Record Type: Journal Article
• Authors: Uwate, Maki; Ichise, Yu‐ki; Shirai, Akihiro; Omasa, Takeshi; Nakae, Taiji; Maseda, Hideaki
• Is Part Of: Microbiology and immunology. Volume 57:Number 4(2013:Apr.)
• Page Start: 263
• Page End: 272
• Publication Date: 2013-04-15
• Subjects: Microbiology -- Periodicals; Immunology -- Periodicals; Allergy and Immunology -- Periodicals; Microbiology -- Periodicals; Microbiologie -- Périodiques; Immunologie -- Périodiques; 579
• DOI: 10.1111/1348-0421.12032
• Languages: English
• ISSNs: 0385-5600

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <sec id="mim12032-sec-0001" sec-type="section"> <p>The NfxC‐type mutant of <italic>Pseudomonas aeruginosa</italic> produces the MexEF‐OprN efflux pump and down‐regulates expression of the quorum‐sensing‐dependent efflux pump MexAB‐OprM and production of virulence factors in the presence of an active transcriptional regulator, MexT. Consequently, these cells are resistant to chloramphenicol and hypersusceptible to β‐lactam antibiotics. An upper negative regulator, MexS, has been assumed to inactivate MexT in wild‐type strains, hence shutting down production of the MexEF‐OprN pump. This observation was, however, reported in only one clinical strain and not confirmed in well‐characterized laboratory strains. Moreover, it is not known whether MexS is involved in the quorum‐sensing‐dependent regulation of virulence factor production. To assess these issues, a plasmid carrying wild‐type <italic>mexS</italic> was introduced into three NfxC‐type mutants from laboratory strains, which carry an impaired <italic>mexS</italic> and unimpaired <italic>mexT</italic>. Unexpectedly, all the transformants produced an increased amount of MexEF‐OprN proteins. Three clinical NfxC strains were similarly transformed and although MexEF‐OprN was undetectable in two of these strains, one produced an increased amount of these proteins, similar to the laboratory strains. These results were interpreted to mean that <italic>P. aeruginosa</italic> takes two separate routes in MexT‐mediated regulation of <italic>mexEF‐oprN</italic> expression: the MexS‐bypassed pathway and MexS‐mediated pathway. On the other hand, the transformants of both the laboratory and clinically derived NfxC‐type cells produced increased amounts of MexAB‐OprM and virulence factors, suggesting that production of these proteins occurs via the MexS‐mediated pathway.</p> </sec> </abstract>