Tween 80 induces a carbon flux rerouting in Mycobacterium tuberculosis

As a means to increase the growth rate and reduce aggregation, Tween 80 is routinely added to growth media during mycobacterial culturing. This detergent has, however, been associated with causing alterations to the morphology, pathogenicity and virulence of these bacteria. In an attempt to better understand the underlying mechanism of these alterations, we investigated the effect of Tween 80 on the metabolomes of a M. tuberculosis lab strain (H37Rv) and multidrug-resistant clinical strain (R179), using GC-GCxTOF-MS metabolomics. The metabolite markers identified indicated Tween 80-induced disparities in the central carbon metabolism of both strains, with an upregulation in the glyoxylate cycle, glucogenogenesis and the pentose phosphate pathway. The results also signified an increased production of mycobacterial biosynthetic precursors such as triacylglycerols, proteinogenic amino acids and nucleotide precursors, in the presence of the detergent. Collectively, these metabolome variations mimic the phenotypic changes observed when M. tuberculosis is grown in vivo, in a lipid rich environment. However, in addition to the increased availability of oleic acid as a carbon source from Tween 80, the observed variations, and the morphological changes associated with the detergent, could also be a result of an overall stress response in these bacteria. This study is the first to identify specific metabolome variations related to the addition of Tween 80 to the growth media during M. tuberculosis culturing. The consideration of these results during the method development and data interpretation phases of future metabolomics investigations will improve the quality of the analyses as well as the credibility of potential research outcomes. These results will also assist in the interpretation of research questions specifically aimed at aspects of mycobacterial metabolism, even when using other methodologies such as transcriptomics or fluxomics.