|dc.description.abstract||Tuberculosis (TB) claims the lives of millions of individuals each year, and is
consequently the world’s second-most deadly infectious disease after acquired
immune deficiency syndrome (AIDS), responsible for 1.4 million deaths in 2010
alone. Developing countries carry the heaviest burden, with the occurrence of
multidrug-resistant (MDR) TB becoming more frequent, making more efficient
vaccination and treatment strategies a necessity to combat this epidemic. The ESX-1
gene cluster (encoding the virulence-associated proteins ESAT-6 and CFP-10) and
the Type Vll secretion system are thought to be responsible for the transport of
extracellular proteins across the hydrophobic, and highly impermeable, cell wall of
Mycobacterium, and consequently are thought to play a role in the virulence of this
organism. To date, our understanding of tuberculosis pathophysiology and virulence
has been described primarily using proteomic and genomic approaches.
Subsequently, using the relatively new research approach called metabolomics, and
interpreting the data using systems biology, we aimed to identify new metabolite
markers that better characterise virulence and the proteins involved, more
specifically related to the ESX-1 gene cluster. Using a GCxGC-TOFMS
metabolomics research approach, we compared the varying metabolomes of M.
smegmatis ESX-1 knock-out (ESX-1ms) to that of the wild-type parent strain and
subsequently identified those metabolite markers differing between these strains.
Multivariate and univariate statistical analyses of the analysed metabolome were
used to identify those metabolites contributing most to the differences seen between
the two sample groups. A general increase in various carbohydrates, amino acids
and lipids, associated with cell wall structure and function, were detected in the
ESX-1ms strain relative to the wild-type parent strain. Additionally, metabolites
associated with the antioxidant system, virulence protein formation and energy
production in these mycobacteria, were also seen to differ between the two groups.
This metabolomics investigation is the first to identify the metabolite markers
confirming the role of the ESX-1 gene cluster with virulence and the underlying
metabolic pathways, as well as its associated role with increased metabolic activity,
growth/replication rates, increased cell wall synthesis and an altered antioxidant
mechanism, all of which are believed to contribute to this organism’s increased
pathogenicity and survival ability.||en_US