Differential Expression of Proteins of Mycobacterium bovis BCG during Adaptation to Anaerobic Non Replicating Persistence

The adaptive mechanisms involved in the establishment of a latent infection with Mycobacterium tuberculosis are not fully understood, but hypoxic condition in the central part of the granulomas is generally believed to be the environment encountered by the pathogen during persistence. In the present study, we followed the adaptive process of Mycobacterium bovis BCG during transition in vitro from activity aerobic growth to a state of anaerobic non-replicating persistence which was characterized by non dividing cells, low metabolic as assayed by luciferase reporter and >1% dissolved oxygen. The response of recombinant M. bovis BCG in aerobic replicating and anaerobic non replicating conditions was investigated. Proteome analysis of differentially expressed mycobacterial proteins during adaptation to anaerobic non-replicating persistence by two-dimensional (2-D) gel electrophoresis, mass spectrometry, and database searching, revealed 34 proteins, out of these 28 proteins showed either unique or increased expression and 6 proteins were observed to be downregulated under the conditions of hypoxia. These proteins are those involved in fatty acid oxidation, intermediary metabolism and respiratory pathways of mycobacteria, suggesting their role in persistence. Identification of proteins by this strategy will help elucidate the adaptive mechanisms in mycobacteria, provide insights into the physiology of latent bacilli and also serve as potential targets for development of new drugs for latent state of tuberculosis. Keywords: Mycobacterium bovis BCG; Proteins; Latent state of tuberculosis; Anaerobic non replicating; 2-D gel electrophoresis; Mass spectrometry