Project Summary Mycobacterium tuberculosis (Mtb) has adapted to survive a wide range of assaults—from our immune response to antimicrobial therapeutics—intended to eradicate the organism. However, the molecular switches that enable Mtb to endure these stresses, to slow replication or to become dormant as a latent tuberculosis infection are not known. Emerging studies on the molecular underpinnings of stress survival point to the activity of the toxin component of Mtb toxin-antitoxin systems in mediating the switch to the non-replicating persistent state characteristic of latent tuberculosis infection. This R21 proposal outlines experiments that test the novel hypothesis that a subset of these toxins do not globally inhibit translation but instead are highly specific tRNases that trigger a combination of ribosome frameshifting and ribosome stalling to surgically manipulate the Mtb proteome as a means to alter the physiology and/or metabolism of this pathogen.