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HOME > J. Microbiol > Volume 58(6); 2020 > Article
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Regulation of the AcrAB efflux system by the quorum-sensing regulator AnoR in Acinetobacter nosocomialis
Bindu Subhadra 1,2, Surya Surendran 1,2, Bo Ra Lim 1,2, Jong Sung Yim 1,2, Dong Ho Kim 1,2, Kyungho Woo 1,2, Hwa-Jung Kim 1,2, Man Hwan Oh 3, Chul Hee Choi 1,2
Journal of Microbiology 2020;58(6):507-518.
DOI: https://doi.org/10.1007/s12275-020-0185-2
Published online: May 27, 2020
1Department of Microbiology, Chungnam National University School of Medicine, Daejeon 35015, Republic of Korea, 2Department of Medical Science, Chungnam National University, Daejeon 34134, Republic of Korea, 3Department of Nanobiomedical Science, Dankook University, Cheonan 31116, Republic of Korea
Corresponding author:  Man Hwan Oh , Tel: +82-42-580-8246, 
Chul Hee Choi , Tel: +82-42-580-8246, 
Received: 7 April 2020   • Revised: 11 May 2020   • Accepted: 11 May 2020
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Abstract

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 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.

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    Regulation of the AcrAB efflux system by the quorum-sensing regulator AnoR in Acinetobacter nosocomialis
    J. Microbiol. 2020;58(6):507-518.   Published online May 27, 2020
    DOI: https://doi.org/10.1007/s12275-020-0185-2
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