Expression profile of mce4 operon of Mycobacterium tuberculosis following environmental stress

Background: The mce4 operon is one of the four mce operons with eight genes ( yrbE4A , yrbE4B , mce4A, mce4B, mce4C, mce4D, mce4E and mce4F) of Mycobacterium tuberculosis. It expresses in the later phase of infection and imports cholesterol for long term survival of the bacilli. To cause latent infection, M. tuberculosis undergoes metabolic reprogramming of its genes to survive in the hostile environment like low availability of oxygen and nutrition depletion inside the host. Objective: To analyze real time expression profile of mce4 operon under various stress conditions. Methods: M. tuberculosis H37Rv was exposed to surface stress (0.1% SDS for 30 min and 90 min in late log and stationary phase of culture), hypoxia (5, 10, 15 and 20 days) and grown in the presence of either glycerol or cholesterol as sole source of carbon. The expression profile of genes of mce4 operon was analyzed by real time PCR. Results: Surface stress induced expression of mce4C and yrbE4B in late log phase on 30 min and 90 min exposure respectively. The SDS exposure for 30 min induced mce4C, mce4D and mce4F in stationary phase. All eight genes were induced significantly on 10th and 15th days of hypoxia and in the presence of cholesterol. Conclusion: Hypoxia and cholesterol are potent factors for the expression of mce4 operon of M. tuberculosis.