Identification using LC-MSn of co-metabolites in the biosynthesis of the polyketide toxin mycolactone by a clinical isolate of Mycobacterium ulceransElectronic supplementary information (ESI) available: Experimental procedures and ESI-CID-MS/MS spectra of mycolactone and the five co-metabolites; MS3 spectrum of m/z 661 from the MS/MS of m/z 749; scheme showing the losses of mass 88 (C4H8O2) during the MS/MS of m/z 749 and the MS3 of m/z 661. See http://www.rsc.org/suppdata/cc/b3/b308163j/