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Identification of fumarate reductase as a potential Mycobacterium tuberculosis virulence factor and as an important factor in antimicrobial susceptibility

University of British Columbia

During an infection, Mycobacterium tuberculosis resides within a phagosome of a macrophage (MΦ), an environment thought to be hypoxic, nitrosative, oxidative and carbohydrate poor. Previous research evaluating which M. tuberculosis genes are important for surviving the harsh MΦ phagosome environment suggested that the fumarate reductase (FRD) enzyme might be an important factor not only for intra-MΦ survival but for M. tuberculosis virulence as well. FRD is used in anaerobic respiration (when oxygen is limiting) and helps maintain a balanced cellular redox state by using fumarate as a terminal electron acceptor. We engineered an M. tuberculosis FRD knock out that demonstrated a decrease in viability in hypoxic conditions, confirming the role of FRD in surviving hypoxia. The M. tuberculosis FRD knock out also showed a statistically significant decrease in intracellular colony forming units 4-days post MΦ infection. This suggested that FRD is also an M. tuberculosis virulence factor. As such, targeting and inhibiting FRD with a drug may be a novel means for treating tuberculosis by preventing M. tuberculosis from performing anaerobic respiration. Putative FRD inhibitors were tested for mycobactericidal activity. Three out of 7 putative FRD inhibitors tested showed mycobactericidal activity in hypoxic conditions, which supported the hypothesis. Additionally, we engineered an Mycobacterium smegmatis strain to express M. tuberculosis FRD. This changed its colony morphology and rendered it more susceptible to a variety of antimicrobials, suggesting that FRD may also affect cell envelope composition. These findings further implicate FRD as a target of interest for novel anti-mycobacterial drug options. In summary, this research gives hope to alleviate the ever growing resistance problem seen in tuberculosis infections by opening up a new route for drug development and discovery.

Text

2011-04-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/33836

Microbiology and Immunology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/