Regulation of the AcrAB efflux system by the quorum-sensing regulator AnoR in Acinetobacter nosocomialis
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Regulation of the AcrAB efflux system by the quorum-sensing regulator AnoR in Acinetobacter nosocomialis§ Bindu Subhadra1,2#, Surya Surendran1,2, Bo Ra Lim1,2, Jong Sung Yim1,2, Dong Ho Kim1,2, Kyungho Woo1,2, Hwa-Jung Kim1,2, Man Hwan Oh3*, and Chul Hee Choi1,2* 1
Department of Microbiology, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea 2 Department of Medical Science, Chungnam National University, Daejeon 34134, Republic of Korea 3 Department of Nanobiomedical Science, Dankook University, Cheonan 31116, Republic of Korea # Present Address: College of Veterinary Medicine, Long Island University, Brookville, New York 11548, USA (Received Apr 7, 2020 / Revised May 11, 2020 / Accepted May 11, 2020)
Multidrug efflux pumps play an important role in antimicrobial resistance and pathogenicity in bacteria. Here, we report the functional characterization of the RND (resistance-nodulation-division) efflux pump, AcrAB, in Acinetobacter nosocomialis. An in silico analysis revealed that homologues of the AcrAB efflux pump, comprising AcrA and AcrB, are widely distributed among different bacterial species. Deletion of acrA and/or acrB genes led to decreased biofilm/pellicle formation and reduced antimicrobial resistance in A. nosocomialis. RNA sequencing and mRNA expression analyses showed that expression of acrA/B was downregulated in a quorum sensing (QS) regulator (anoR)-deletion mutant, indicating transcriptional activation of the acrAB operon by AnoR in A. nosocomialis. Bioassays showed that secretion of N-acyl homoserine lactones (AHLs) was unaffected in acrA and acrB deletion mutants; however, AHL secretion was limited in a deletion mutant of acrR, encoding the acrAB regulator, AcrR. An in silico analysis indicated the presence of AcrR-binding motifs in promoter regions of anoI (encoding AHL synthase) and anoR. Specific binding of AcrR was confirmed by electrophoretic mobility shift assays, which revealed that AcrR binds to positions -214 and -217 bp upstream of the translational start sites of anoI and anoR, respectively, demonstrating transcriptional regulation of these QS genes by AcrR. The current study further addresses the possibility that AcrAB is controlled by the osmotic stress regulator, OmpR, in A. nosocomialis. Our data demonstrate that the AcrAB efflux pump plays a crucial role in biofilm/pellicle formation and *For correspondence. (M.H. Oh) E-mail: [email protected]; Tel.: +8241-529-6242; Fax: +82-41-559-7863 / (C.H. Choi) E-mail: [email protected]; Tel.: +82-42-580-8246; Fax: +82-42-585-3686 § Supplemental material for this article may be found at http://www.springerlink.com/content/120956. Copyright G2020, The Microbiological Society of Korea
antimicrobial resistance in A. nosocomialis, and is under the transcriptional control of a number of regulators. In addition, the study emphasizes the interrelationship of QS and AcrAB efflux systems in A. nosocomialis. Keywords: Acinetobacter nosocomialis, efflux pump, quorum sensing, AcrAB Int
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