Identifying and Characterizing Novel Genes Involved in Glutathione Sensitivity.
By: Raheem Lawrence
One third of the earth population is infected with Mycobacterium tuberculosis (M.tb) the causative agent for tuberculosis (TB). Of that one third, half are infected with the multi-drug resistant strain which kills more than 2 million people yearly. Tuberculosis is often viewed as disease of the poor, as majority of document cases of M.tb are in developing countries which makes advancing our knowledge of this disease of great importance. M.tb is an aerobic gram positive like bacterium that infects individuals through inhalation of aerosols, upon inhalation the bacteria resides in the linings of the lungs and rapidly proliferate in the oxygen rich environment. To prevent the continuous growth of the M.tb , macrophages which function as part of the lung immune system quickly engulf the bacteria by phagocytosis. The invading bacteria are equipped with an innate mechanism to protect itself from the immune response by first lowering the local pH and then blocking phago-lysosomal fusion. This allows the bacteria to grow and persist within the macrophage and prevent its cell to be lysed. In response, the immune defense exposes the bacteria to high levels of oxidative radicals such as reactive oxygen and nitrogen intermediates. However these intermediates are ineffective against the bacteria as well as toxic to host cells, therefore the immune response produces glutathione (GSH) protect itself.
Glutathione is a is a thiol based detoxification molecule that protects the host cell from oxidative radicals, recent studies conducted by our laboratory has observed that high concentrations of GSH are toxic in early in-vitro models used with Mycobacterium bovis (BCG) .BCG was chosen because of its availability to be used in a undergraduate facility and also shares 99% genetic similarity to M.tb and is used as a model organism in its study. From this study we have identified GSH as a possible compound to aid in the fight against M.tb, but the mechanisms behind GSH toxicity is still unknown and there is a need for further research to be conducted. The overarching goal of this research is to use transposon mutagenesis to create a panel of mutants to genetically classify the specific loci involved in GSH sensitivity. If successful this will lead us one step further in understanding the mechanism behind GSH stress and possibly help we to utilize GSH to make vaccines and anti-microbial to control the rampant spread of TB world wide.