{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T06:59:57Z","timestamp":1785308397296,"version":"3.55.0"},"reference-count":49,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T00:00:00Z","timestamp":1785283200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008871","name":"Yunnan Provincial Science and Technology Department","doi-asserted-by":"publisher","award":["Grant No. 202301BA070001-097"],"award-info":[{"award-number":["Grant No. 202301BA070001-097"]}],"id":[{"id":"10.13039\/501100008871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"\n Background<\/jats:title>\n \n The global transcriptional regulator MarA drives multidrug resistance in\n Escherichia coli<\/jats:italic>\n . MarA regulation of Resistance-Nodulation-Cell Division (RND) efflux pumps such as AcrAB-TolC is well established, but its control over ATP-binding cassette (ABC)-type efflux pumps remains unclear. The ABC efflux pump YadGH exports macrolides, yet its upstream transcriptional regulation is unknown.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Deletion mutants \u0394\n marA<\/jats:italic>\n , \u0394\n yadG<\/jats:italic>\n , \u0394\n yadH<\/jats:italic>\n , and double mutants were constructed in\n E. coli<\/jats:italic>\n K-12 MG1655. Minimum inhibitory concentrations (MICs) of 15 antibiotics were measured by broth microdilution.\n YadGH<\/jats:italic>\n transcription was assessed by qRT-PCR. MarA binding to the\n yadGH<\/jats:italic>\n promoter was verified by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation quantitative real-time PCR (ChIP-qPCR). Biofilm formation and swarming motility were assayed.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n MIC assays revealed that single deletions of\n yadG<\/jats:italic>\n or\n yadH<\/jats:italic>\n had negligible effects on most antibiotics. However, in the \u0394\n acrB<\/jats:italic>\n background, deleting\n yadGH<\/jats:italic>\n (\u0394\n acrB<\/jats:italic>\n \u0394\n yadG<\/jats:italic>\n and \u0394\n acrB<\/jats:italic>\n \u0394\n yadH<\/jats:italic>\n ) increased sensitivity to erythromycin and tylosin, indicating that YadGH conditionally contributes to macrolide resistance specifically when the major efflux pump AcrB is absent. qRT-PCR showed that\n yadGH<\/jats:italic>\n transcription is induced in a MarA-dependent manner in\n E. coli<\/jats:italic>\n K-12. The \u0394\n marA<\/jats:italic>\n mutant phenocopied this susceptibility profile, supporting the role of\n yadGH<\/jats:italic>\n as a downstream effector of MarA within this genetic context. ChIP-qPCR confirmed MarA binding to the\n yadGH<\/jats:italic>\n promoter, and EMSA mapped a degenerate marbox motif upstream of the\n yadG<\/jats:italic>\n start codon. Genome annotation lists\n yadG<\/jats:italic>\n and\n yadH<\/jats:italic>\n as a two-gene operon.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n MarA binds to the\n yadGH<\/jats:italic>\n promoter and positively regulates its transcription. YadGH serves as a conditional auxiliary efflux pump for macrolides when AcrAB-TolC is absent. Deletion of\n yadGH<\/jats:italic>\n also affects biofilm formation and motility.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fmicb.2026.1902331","type":"journal-article","created":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T06:02:45Z","timestamp":1785304965000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["MarA binds and activates the ABC efflux pump YadGH to confer conditional macrolide resistance in AcrB-deficient Escherichia coli"],"prefix":"10.3389","volume":"17","author":[{"given":"Zhenyue","family":"Feng","sequence":"first","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]},{"name":"Yunnan Engineering Research Center of Green Planting and Processing of Gastrodia, Zhaotong University","place":["Zhaotong, China"]},{"name":"Institute for Advanced Study on Ecological Agriculture and Biodiversity of the Yunnan-Guizhou Plateau, Zhaotong University","place":["Zhaotong, China"]},{"name":"Yunnan Key Laboratory of Smart Villages and Agri-Cultural-Tourism Integration, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiqin","family":"Li","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Biao","family":"Ma","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hong","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanli","family":"Li","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liangrong","family":"Bao","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Defu","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Agronomy and Life Sciences, Zhaotong University","place":["Zhaotong, China"]},{"name":"Yunnan Engineering Research Center of Green Planting and Processing of Gastrodia, Zhaotong University","place":["Zhaotong, China"]},{"name":"Institute for Advanced Study on Ecological Agriculture and Biodiversity of the Yunnan-Guizhou Plateau, Zhaotong University","place":["Zhaotong, China"]},{"name":"Yunnan Key Laboratory of Smart Villages and Agri-Cultural-Tourism Integration, Zhaotong University","place":["Zhaotong, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,7,29]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"2067","DOI":"10.1128\/AAC.41.10.2067","article-title":"Regulation of chromosomally mediated multiple antibiotic resistance: The mar regulon.","volume":"41","author":"Alekshun","year":"1997","journal-title":"Antimicrob. 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