{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,10]],"date-time":"2026-07-10T13:29:39Z","timestamp":1783690179977,"version":"3.55.0"},"reference-count":55,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,3,24]],"date-time":"2022-03-24T00:00:00Z","timestamp":1648080000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p><jats:italic>Mycobacterium ulcerans<\/jats:italic> is the causative agent of Buruli ulcer (BU), the third most common mycobacterial infection. Virulent <jats:italic>M. ulcerans<\/jats:italic> secretes mycolactone, a polyketide toxin. Most observations of <jats:italic>M. ulcerans<\/jats:italic> infection are described as an extracellular milieu in the form of a necrotic ulcer. While some evidence exists of an intracellular life cycle for <jats:italic>M. ulcerans<\/jats:italic> during infection, the exact role that mycolactone plays in this process is poorly understood. Many previous studies have relied upon the addition of purified mycolactone to cell-culture systems to study its role in <jats:italic>M. ulcerans<\/jats:italic> pathogenesis and host-response modulation. However, this sterile system drastically simplifies the <jats:italic>M. ulcerans<\/jats:italic> infection model and assumes that mycolactone is the only relevant virulence factor expressed by <jats:italic>M. ulcerans<\/jats:italic>. Here we show that the addition of purified mycolactone to macrophages during <jats:italic>M. ulcerans<\/jats:italic> infection overcomes the bacterial activation of the mechanistic target of rapamycin (mTOR) signaling pathway that plays a substantial role in regulating different cellular processes, including autophagy and apoptosis. To further study the role of mycolactone during <jats:italic>M. ulcerans<\/jats:italic> infection, we have developed an inducible mycolactone expression system. Utilizing the mycolactone-deficient <jats:italic>Mul<\/jats:italic>::Tn118 strain that contains a transposon insertion in the putative beta-ketoacyl transferase (<jats:italic>mup045<\/jats:italic>), we have successfully restored mycolactone production by expressing <jats:italic>mup045<\/jats:italic> in a tetracycline-inducible vector system, which overcomes <jats:italic>in-vitro<\/jats:italic> growth defects associated with constitutive complementation. The inducible mycolactone-expressing bacteria resulted in the establishment of infection in a murine footpad model of BU similar to that observed during the infection with wild-type <jats:italic>M. ulcerans<\/jats:italic>. This mycolactone inducible system will allow for further analysis of the roles and functions of mycolactone during <jats:italic>M. ulcerans<\/jats:italic> infection.<\/jats:p>","DOI":"10.3389\/fimmu.2022.750643","type":"journal-article","created":{"date-parts":[[2022,3,29]],"date-time":"2022-03-29T06:23:29Z","timestamp":1648535009000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":6,"title":["Induced Synthesis of Mycolactone Restores the Pathogenesis of Mycobacterium ulcerans In Vitro and In Vivo"],"prefix":"10.3389","volume":"13","author":[{"given":"Emily","family":"Strong","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bryan","family":"Hart","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jia","family":"Wang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria 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