Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606
In this study, we show that <i>Acinetobacter baumannii</i> ATCC 19606 harbors two sets of <i>ohrR-ohr</i> genes, respectively encoded in chromosomal DNA and a pMAC plasmid. We found no significant difference in organic hydroperoxide (OHP) resistance between strains with or wi...
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MDPI AG
2021-03-01
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| Online Access: | https://www.mdpi.com/2076-2607/9/3/629 |
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| author | Shih-Jie Chen Hung-Yu Shu Guang-Huey Lin |
| author_facet | Shih-Jie Chen Hung-Yu Shu Guang-Huey Lin |
| author_sort | Shih-Jie Chen |
| collection | DOAJ |
| description | In this study, we show that <i>Acinetobacter baumannii</i> ATCC 19606 harbors two sets of <i>ohrR-ohr</i> genes, respectively encoded in chromosomal DNA and a pMAC plasmid. We found no significant difference in organic hydroperoxide (OHP) resistance between strains with or without pMAC. However, a disk diffusion assay conducted by exposing wild-type, <i>∆ohrR-C</i>, <i>C</i> represented gene on chromosome, or <i>∆ohr-C</i> single mutants, or <i>∆ohrR</i>-<i>C∆ohr</i>-<i>C</i> double mutants to <i>tert</i>-butyl hydroperoxide (<i>t</i>BHP) found that the <i>ohrR-p-ohr-p</i> genes, <i>p</i> represented genes on pMAC plasmid, may be able to complement the function of their chromosomal counterparts. Interestingly, <i>∆ohr-C</i> single mutants generated in <i>A. baumannii</i> ATCC 17978, which does not harbor pMAC, demonstrated delayed exponential growth and loss of viability following exposure to 135 μg of <i>t</i>BHP. In a survival assay conducted with <i>Galleria mellonella</i> larvae, these mutants demonstrated almost complete loss of virulence. Via an electrophoretic mobility shift assay (EMSA), we found that OhrR-C was able to bind to the promoter regions of both chromosomal and pMAC <i>ohr</i>-<i>p</i> genes, but with varying affinity. A gain-of-function assay conducted in <i>Escherichia coli</i> showed that OhrR-C was not only capable of suppressing transformed <i>ohr-C</i> genes but may also repress endogenous enzymes. Taken together, our findings suggest that chromosomal <i>ohrR-C-ohr-C</i> genes act as the major system in protecting <i>A. baumannii</i> ATCC 19606 from OHP stresses, but the <i>ohrR-p-ohr-p</i> genes on pMAC can provide a supplementary protective effect, and the interaction between these genes may affect other aspects of bacterial viability, such as growth and virulence. |
| first_indexed | 2024-03-10T13:07:42Z |
| format | Article |
| id | doaj.art-651886ac4f11458280b15d1dc6622dc1 |
| institution | Directory Open Access Journal |
| issn | 2076-2607 |
| language | English |
| last_indexed | 2024-03-10T13:07:42Z |
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| spelling | doaj.art-651886ac4f11458280b15d1dc6622dc12023-11-21T10:57:59ZengMDPI AGMicroorganisms2076-26072021-03-019362910.3390/microorganisms9030629Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606Shih-Jie Chen0Hung-Yu Shu1Guang-Huey Lin2Master Program in Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien 97004, TaiwanDepartment of Bioscience Technology, Chang Jung Christian University, Tainan 71101, TaiwanMaster Program in Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien 97004, TaiwanIn this study, we show that <i>Acinetobacter baumannii</i> ATCC 19606 harbors two sets of <i>ohrR-ohr</i> genes, respectively encoded in chromosomal DNA and a pMAC plasmid. We found no significant difference in organic hydroperoxide (OHP) resistance between strains with or without pMAC. However, a disk diffusion assay conducted by exposing wild-type, <i>∆ohrR-C</i>, <i>C</i> represented gene on chromosome, or <i>∆ohr-C</i> single mutants, or <i>∆ohrR</i>-<i>C∆ohr</i>-<i>C</i> double mutants to <i>tert</i>-butyl hydroperoxide (<i>t</i>BHP) found that the <i>ohrR-p-ohr-p</i> genes, <i>p</i> represented genes on pMAC plasmid, may be able to complement the function of their chromosomal counterparts. Interestingly, <i>∆ohr-C</i> single mutants generated in <i>A. baumannii</i> ATCC 17978, which does not harbor pMAC, demonstrated delayed exponential growth and loss of viability following exposure to 135 μg of <i>t</i>BHP. In a survival assay conducted with <i>Galleria mellonella</i> larvae, these mutants demonstrated almost complete loss of virulence. Via an electrophoretic mobility shift assay (EMSA), we found that OhrR-C was able to bind to the promoter regions of both chromosomal and pMAC <i>ohr</i>-<i>p</i> genes, but with varying affinity. A gain-of-function assay conducted in <i>Escherichia coli</i> showed that OhrR-C was not only capable of suppressing transformed <i>ohr-C</i> genes but may also repress endogenous enzymes. Taken together, our findings suggest that chromosomal <i>ohrR-C-ohr-C</i> genes act as the major system in protecting <i>A. baumannii</i> ATCC 19606 from OHP stresses, but the <i>ohrR-p-ohr-p</i> genes on pMAC can provide a supplementary protective effect, and the interaction between these genes may affect other aspects of bacterial viability, such as growth and virulence.https://www.mdpi.com/2076-2607/9/3/629<i>Acinetobacter baumannii</i>OhrOhrRorganic hydroperoxideantibiotic resistancebacterial viability |
| spellingShingle | Shih-Jie Chen Hung-Yu Shu Guang-Huey Lin Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 Microorganisms <i>Acinetobacter baumannii</i> Ohr OhrR organic hydroperoxide antibiotic resistance bacterial viability |
| title | Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 |
| title_full | Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 |
| title_fullStr | Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 |
| title_full_unstemmed | Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 |
| title_short | Regulation of <i>tert</i>-Butyl Hydroperoxide Resistance by Chromosomal OhrR in <i>A. baumannii</i> ATCC 19606 |
| title_sort | regulation of i tert i butyl hydroperoxide resistance by chromosomal ohrr in i a baumannii i atcc 19606 |
| topic | <i>Acinetobacter baumannii</i> Ohr OhrR organic hydroperoxide antibiotic resistance bacterial viability |
| url | https://www.mdpi.com/2076-2607/9/3/629 |
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