Metabolomic studies allow the discovery and simultaneous visualisation of entire biochemical pathways directly.
The information gathered by combination of metabolomics and stable isotope tracing is not accessible by genomic, transcriptomic or proteomic means and is, by definition, the representation of all regulatory cascades, and therefore the closest possible readout of phenotype.
Using these methodologies we intend to evaluate regulatory, kinetic and topological aspects of M. tuberculosis metabolic network. In a second step, we would like to define which nodes of M. tuberculosis metabolic network are 'connected' to the macrophage metabolic network, in an attempt of understanding the metabolic basis for infection.
In a series of studies carried out in collaboration with the Neyrolles group in France, we were able to assign the substrate specificity and metabolic role of two mycobacterial nutrient transporters (Figure 3). Their biochemical function was then used to understand their role during infection. These studies represent the first applications of high-resolution mass spectrometry-based metabolomic profiling and stable isotope tracing to assign function to orphan membrane transporters.
We are currently expanding these studies to other orphan transporters in an effort to map unknown nutrient acquisition pathways in M. tuberculosis.
Figure 3. Schematic representation of some of the steps involved in L-Asp and L-Asn uptake and their utilization as nitrogen sources in M. tuberculosis. AnsP1 and AnsP2 function were assigned using unbiased metabolomics profiling of M. tuberculosis mutants