Multi-Stress Induction of the MbcTA Bactericidal Toxin-Antitoxin System.

MbcTA is a type II toxin/antitoxin (TA) system of . The MbcT toxin triggers mycobacterial cell death in vitro and in vivo through the phosphorolysis of the essential metabolite NAD and its bactericidal activity is neutralized by physical interaction with its cognate antitoxin MbcA. Therefore, the MbcTA system appears as a promising target for the development of novel therapies against tuberculosis, through the identification of compounds able to antagonize or destabilize the MbcA antitoxin. Here, the expression of the operon and its regulation were investigated. A dual fluorescent reporter system was developed, based on an integrative mycobacterial plasmid that encodes a constitutively expressed reporter, serving as an internal standard for monitoring mycobacterial gene expression, and an additional reporter, dependent on the promoter under investigation. This system was used both in and in the fast growing model species to: (i) assess the autoregulation of ; (ii) perform a genetic dissection of the promoter/operator region; and (iii) explore the regulation of transcription from the promoter (P) in a variety of stress conditions, including in vivo in mice and in macrophages.