A third of the world's population is infected with Mycobacterium tuberculosis (MTB) and most of these infections are in a latent state. Tubercle bacilli can remain inactive in lung lesions only to emerge decades later as new outbreaks of tuberculosis. Current therapy for tuberculosis often involves the administration of multiple antimicrobial agents over several months, probably because bacilli exist in a drug tolerant, dormant-like state in tubercle lesions. Understanding the physiology of bacilli during the latent infection phase is central to the goal of controlling and ultimately eradicating tuberculosis. We have demonstrated that as aerobic respiration is impeded (by reduced oxygen or by the presence of nitric oxide), bacilli strongly induce a co-regulated 48-gene genetic program called the """"""""dormancy regulon"""""""". This regulon encodes a program required for adaptation to a long-term viable """"""""dormant"""""""" or non-proliferating state. Bacillus survival during an anaerobic non-proliferating state requires conservation of energy, alternative mechanisms to maintain redox balance, and mechanisms to protect DNA and proteins. Our working hypothesis is: The dormancy regulon is a genetic program that confers survival to MTB during latency. To test this hypothesis we will investigate key aspects of dormant MTB that involve the role of dormancy regulon proteins in nucleotide and nucleic acid biology during dormancy. The research proposed herein is pivotal to understanding how the tubercle bacillus survives indefinitely during latent infection, and characterizes numerous candidate targets for drug development. This study compliments a collaboration with the Russian Research Center for Molecular Diagnostics and Therapy. A joint proposal will be submitted to the US Department of Health and Human Services Biotechnology Engagement Program that will address aspects of dormant MTB in human infection.
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