Separation and characterization of individual mycolic acids in representative mycobacteria

Total mycolic acid methyl ester fractions were isolated from 24 representat ives of Mycobacterium tuberculosis, Mycobacterium bovis (including BCG), My cobacterium microti, Mycobacterium kansasii and Mycobacterium avium. The to tal mycolate functional group composition was estimated from H-1-NMR spectr a. Mycolates were separated into alpha -mycolates, methoxymycolates and ket omycolates and each class was further separated by argentation chromatograp hy into mycolates with no double bonds, with one trans-double bond and with one cis-double bond. Mass spectrometry revealed the mycolate chain lengths and H-1-NMR the cis- and trans-double bond and cyclopropane ring content. The same species had similar mycolate profiles; the major type of each clas s had cis- or trans-cyclopropane rings and lacked double bonds. Minor propo rtions of possible unsaturated precursors of the cyclopropane mycolates wer e commonly encountered. Among unusual a-mycolates, many strains had tricycl opropyl components with chains extended by 6 to 8 carbons. Significantly, M . tuberculosis (Canetti) and M. avium had alpha -mycolates with a trans-dou ble bond and cyclopropane ring, whose chain lengths suggested a relationshi p to possible precursors of oxygenated mycolates. The methoxy and ketomycol ates from a majority of M. tukerculosis strains had minor amounts of compon ents with additional cyclopropane rings, some of whose chains were also ext ended by 6 to 8 carbons. These latter mycolates were major components in th e attenuated M. tukerculosis H37Ra strain, whose mycolate profile was disti nct from those of other strains of M. tukerculosis.