{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,6]],"date-time":"2026-02-06T23:50:15Z","timestamp":1770421815362,"version":"3.49.0"},"reference-count":32,"publisher":"American Society for Microbiology","issue":"2","license":[{"start":{"date-parts":[[2025,2,4]],"date-time":"2025-02-04T00:00:00Z","timestamp":1738627200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2025,2,4]],"date-time":"2025-02-04T00:00:00Z","timestamp":1738627200000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/501100001809","name":"MOST | National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["82102404"],"award-info":[{"award-number":["82102404"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100001809","name":"MOST | National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["82372262"],"award-info":[{"award-number":["82372262"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100003399","name":"Science and Technology Commission of Shanghai Municipality","doi-asserted-by":"crossref","award":["23YF1404100"],"award-info":[{"award-number":["23YF1404100"]}],"id":[{"id":"10.13039\/501100003399","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Microbiol Spectr"],"published-print":{"date-parts":[[2025,2,4]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n          <jats:sec>\n            <jats:title\/>\n            <jats:p>\n              RamA is an intrinsic regulator in\n              <jats:italic>Klebsiella pneumoniae<\/jats:italic>\n              , belonging to the AraC family of transcription factors and conferring a multidrug resistance phenotype, especially for tetracycline-class antibiotics. The ATP-binding cassette transporters MlaFEDCB in bacteria play essential roles in functions essential for cell survival and intrinsic resistance to many antibiotics. We found deletion of\n              <jats:italic>ramA<\/jats:italic>\n              resulted in a fivefold decrease in the transcriptional levels of the\n              <jats:italic>mlaFEDCB<\/jats:italic>\n              operon. After complementation with ramA, the transcriptional levels were comparable to those of wild-type strain. Furthermore, an electrophoretic mobility shift assay showed that RamA could bind to the promoter region of\n              <jats:italic>mlaEFDCB<\/jats:italic>\n              operon, which confirmed RamA is an activator of\n              <jats:italic>mlaEFDCB<\/jats:italic>\n              operon. The\n              <jats:italic>mlaEFDCB<\/jats:italic>\n              operon could mildly mediate resistance to the tetracycline family of antibiotics under RamA regulation. The MIC (minimum inhibitory concentration) of tigecycline decreased fourfold, and the MIC of doxycycline, minocycline, and eravacycline decreased twofold after\n              <jats:italic>mlaE<\/jats:italic>\n              -knockout. The\n              <jats:italic>ramA<\/jats:italic>\n              - and\n              <jats:italic>mlaE<\/jats:italic>\n              -knockout strains exhibited greater sensitivity to sodium dodecyl sulfate (SDS)-EDTA than the wild-type. Growth of \u0394\n              <jats:italic>ramA<\/jats:italic>\n              cells was severely compromised in 0.25\/0.5% SDS and 0.55 mM EDTA, and this sensitivity was restored by complementation with\n              <jats:italic>ramA<\/jats:italic>\n              and\n              <jats:italic>mlaE<\/jats:italic>\n              . This study demonstrates that RamA can directly regulate the\n              <jats:italic>malEFEDCB<\/jats:italic>\n              operon, thereby mediating resistance to tetracycline-class antibiotics, contributing to the stability of bacterial membranes in\n              <jats:italic>K. pneumoniae<\/jats:italic>\n              . We identified a novel signal pathway in which RamA mediates multidrug resistance of\n              <jats:italic>K. pneumoniae<\/jats:italic>\n              , leading to new ideas for the development of novel antimicrobial therapeutics, therefore deserving further comprehensive study.\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>IMPORTANCE<\/jats:title>\n            <jats:p>\n              Multidrug-resistant and extensively drug-resistant\n              <jats:italic>Klebsiella pneumoniae<\/jats:italic>\n              have emerged as significant global health concerns resulting in high mortality rates. Although previous research has investigated the maintenance of lipid asymmetry (Mla) pathway, the extent to which it mediates antimicrobial resistance in\n              <jats:italic>K. pneumoniae<\/jats:italic>\n              and the underlying upstream regulatory mechanisms remain unclear. In this study, we sought to determine at the molecular level how the AraC-type global regulator RamA directly regulates mlaFEDCB, which mediates resistance to tetracycline-class antibiotics and the stability of bacterial membranes in\n              <jats:italic>K. pneumoniae<\/jats:italic>\n              .\n            <\/jats:p>\n          <\/jats:sec>","DOI":"10.1128\/spectrum.01728-24","type":"journal-article","created":{"date-parts":[[2024,12,31]],"date-time":"2024-12-31T13:01:03Z","timestamp":1735650063000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":4,"title":["RamA upregulates the ATP-binding cassette transporter\n            <i>mlaFEDCB<\/i>\n            to mediate resistance to tetracycline-class antibiotics and the stability of membranes in\n            <i>Klebsiella pneumoniae<\/i>"],"prefix":"10.1128","volume":"13","author":[{"given":"Xiaoyu","family":"Zhao","sequence":"first","affiliation":[{"name":"Institute of Antibiotics, Huashan Hospital, Fudan University","place":["Shanghai, China"]},{"name":"Key Laboratory of Clinical Pharmacology of Antibiotics, National Heath Commission","place":["Shanghai, China"]},{"name":"Institute of Microbes and Infections, Huashan Hospital, Fudan University","place":["Shanghai, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yixin","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute of Antibiotics, Huashan Hospital, Fudan University","place":["Shanghai, China"]},{"name":"Key Laboratory of Clinical Pharmacology of Antibiotics, National Heath Commission","place":["Shanghai, China"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mohan","family":"Ju","sequence":"additional","affiliation":[{"name":"Institute of Antibiotics, Huashan Hospital, Fudan 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