Possible intermediates in the biosynthesis of mycoside B by Mycobacterium microti

Two lipids were isolated from Mycobacterium microti which became labelled when the cells were grown in the presence of [2-14C]propionate. They were purified by thin-layer chromatography and studied by chemical degradation and mass spectrometry. The lipids were identified as phenolphthiocerol dimycocerosate and phenolphthiodiolone dimycocerosate, the aglycosyl derivatives of mycoside B, the phenolic glycolipid produced by M. microti. Cell-free extracts of the organism were able to glycosylate the lipids to form mycoside B in vitro. It is probable that the lipids are intermediates in the biosynthesis of phenolic glycolipids by mycobacteria.