{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,6,25]],"date-time":"2026-06-25T17:50:50Z","timestamp":1782409850373,"version":"3.54.5"},"posted":{"date-parts":[[2026,6,23]]},"group-title":"Microbiology","reference-count":60,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,6,23]],"date-time":"2026-06-23T00:00:00Z","timestamp":1782172800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,6,23]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  <jats:italic>Clostridioides difficile<\/jats:italic>\n                  is an urgent threat to human health. Current treatments for\n                  <jats:italic>C. difficile<\/jats:italic>\n                  infections (CDIs) are antibiotics and microbiome restoration therapy (MRT) for recurrent cases. However, antibiotics contribute to antibiotic resistance and recurrent CDIs and the long-term sustainability and accessibility of MRTs remains to be determined. Since a dysbiotic gut microbiome is the primary risk factor for CDI, a better understanding of the interactions between\n                  <jats:italic>C. difficile<\/jats:italic>\n                  , the microbiome, and the host will aid development of treatments with improved precision. Emerging evidence supports that butyrate, a prominent end product of gut microbiome metabolism, is a key determinant of\n                  <jats:italic>C. difficile<\/jats:italic>\n                  pathogenesis. Notably,\n                  <jats:italic>C. difficile<\/jats:italic>\n                  releases more of its toxins TcdA and TcdB in butyrate-rich environments. Here, we demonstrate that butyrate-dependent toxin release is not driven by two previously characterized modes of toxin release (e.g., TcdE-dependent secretion or Cwp19-dependent autolysis). Instead, butyrate enhances the expression of a broadly conserved endolysin (EndD), which is responsible for butyrate-dependent toxin release. We additionally demonstrate that\n                  <jats:italic>endD<\/jats:italic>\n                  -dependent toxin release does not universally occur under all growth conditions and that its expression is dependent on the late-stage sporulation sigma factor SigK. Overall, our findings provide deeper insight into butyrate-dependent effects on\n                  <jats:italic>C. difficile<\/jats:italic>\n                  pathogenesis and set the stage for future work to better understand the molecular and genetic underpinnings of\n                  <jats:italic>endD<\/jats:italic>\n                  regulation.\n                <\/jats:p>","DOI":"10.64898\/2026.06.22.733756","type":"posted-content","created":{"date-parts":[[2026,6,24]],"date-time":"2026-06-24T05:25:16Z","timestamp":1782278716000},"source":"Crossref","is-referenced-by-count":0,"title":["EndD mediates butyrate-dependent toxin release in\n                  <i>Clostridioides difficile<\/i>"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-1530-4301","authenticated-orcid":false,"given":"Horia A.","family":"Dobrila","sequence":"first","affiliation":[{"name":"Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA"},{"name":"Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA"},{"name":"Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Henrieta","family":"Licha","sequence":"additional","affiliation":[{"name":"Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew J.","family":"Hryckowian","sequence":"additional","affiliation":[{"name":"Department of Medicine, Division of Gastroenterology and Hepatology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA"},{"name":"Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026062510401260000_2026.06.22.733756v1.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1408913"},{"key":"2026062510401260000_2026.06.22.733756v1.2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1910215"},{"key":"2026062510401260000_2026.06.22.733756v1.3","doi-asserted-by":"publisher","DOI":"10.1086\/520276"},{"key":"2026062510401260000_2026.06.22.733756v1.4","doi-asserted-by":"publisher","DOI":"10.1016\/S0195-6701(98)90019-6"},{"key":"2026062510401260000_2026.06.22.733756v1.5","first-page":"e00135","article-title":"Clostridioides difficile infection: history, epidemiology, risk factors, prevention, clinical manifestations, treatment, and future options","volume":"37","year":"2024","journal-title":"Clinical Microbiology Reviews"},{"key":"2026062510401260000_2026.06.22.733756v1.6","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1007\/s40121-024-00919-0","article-title":"A Systematic Literature Review on Risk Factors for and Timing of Clostridioides difficile Infection in the United States","volume":"13","year":"2024","journal-title":"Infect Dis Ther"},{"key":"2026062510401260000_2026.06.22.733756v1.7","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-2036.2011.04984.x"},{"key":"2026062510401260000_2026.06.22.733756v1.8","doi-asserted-by":"crossref","unstructured":"Di Bella, S. , Ascenzi, P. , Siarakas, S. , Petrosillo, N. & Di Masi, A . 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