The osmotic stress response operon betIBA is under the functional regulation of BetI and the quorum-sensing regulator An
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The osmotic stress response operon betIBA is under the functional regulation of BetI and 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*
finely tuned by various feedback loops depending on osmolarity conditions. Keywords: Acinetobacter nosocomialis, osmotic stress, quorum sensing, BetI
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 Apr 28, 2020 / Accepted May 12, 2020)
Adaptation to changing environmental conditions is crucial for the survival of microorganisms. Bacteria have evolved various mechanisms to cope with osmotic stress. Here, we report the identification and functional characterization of the osmotic stress response operon, betIBA, in Acinetobacter nosocomialis. The betIBA operon encodes enzymes that are important for the conversion of choline to the osmoprotectant, glycine betaine. The betIBA operon is polycistronic and is under the regulation of the first gene, betI, of the same operon. A bioinformatics analysis revealed the presence of a BetI-binding motif upstream of the betIBA operon, and electrophoretic mobility shift assays confirmed the specific binding of BetI. An mRNA expression analysis revealed that expression of betI, betB, and betA genes is elevated in a betIeletion mutant compared with the wild type, confirming that the autorepressor BetI represses the betIBA operon in A. nosocomialis. We further found that the betIBA operon is under the transcriptional control of the quorum-sensing (QS) regulator, AnoR in, A. nosocomialis. A subsequent analysis of the impact of BetI on expression of the QS genes, anoR and anoI, demonstrated that BetI acts as a repressor of anoR and anoI. In addition, it was noticed that the osmotic stress response regulator, OmpR might play an important role in controlling the expression of betIBA operon in A. nosocomialis. Collectively, these data demonstrate that QS and osmotic stress-response systems are correlated in A. nosocomialis and that the expression of genes in both systems is *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
Introduction Adaptation to osmostress is crucial for bacteria in almost all ecosystems, as they are often exposed to low water activity and even desiccation.
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