Title |
Regulation of the AcrAB efflux system by the quorum-sensing regulator AnoR in Acinetobacter nosocomialis |
Author |
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* |
Address |
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 |
Bibliography |
Journal of Microbiology, 58(6),507–518, 2020,
|
DOI |
10.1007/s12275-020-0185-2
|
Key Words |
Acinetobacter nosocomialis, efflux pump, quorum
sensing, AcrAB |
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. |