Extraction and Purification of Mycobacterial Mycolic Acids

Abstract

Mycolic acids are major long-chain fatty acids, containing up to 80-90 carbon atoms that represent essential components of the mycobacterial cell wall (Pawelczyk and Kremer, 2014). Each mycobacterial species possesses a specific mycolic acid profile characterized by various chemical modifications that decorate the lipid. Mycolic acids play a critical role in the architecture and impermeability of the cell envelope, hence the natural resistance of mycobacteria to most antibiotic treatments. They are also key determinants of virulence in pathogenic species, including Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis. In addition, they are known as the primary target of several first-line and second-line antitubercular drugs. Thus, the unique enzymes involved in the mycolic acid biosynthetic pathway represent an attractive reservoir of targets for future chemotherapy whose developments are particularly warranted in the context of multi-drug-resistant and extensively-drug-resistant strains of M. tuberculosis. Herein, we describe a protocol to extract the mycolic acids from mycobacteria. Purification of the various subspecies may be particularly useful for subsequent structural studies involving mass spectrometry or NMR. The qualitative and quantitative biochemical characterization of the mycolic acid pattern by thin layer chromatography can be used to address how drugs alter mycolic acid biosynthesis (Alahari et al., 2007, Hartkoorn et al., 2012), to study the phenotypes of genetically modified mutants affected in this metabolic pathway (Bhatt et al., 2007) or to unravel new mycolic acid regulatory mechanisms (Vilcheze et al., 2014). The same protocol can be applied to all mycobacteria, including environmental and pathogenic species.