Heterologous Production of 1-Tuberculosinyladenosine in Mycobacterium kansasii Models Pathoevolution towards the Transcellular Lifestyle of Mycobacterium tuberculosis.

is an environmental nontuberculous mycobacterium that causes opportunistic tuberculosis-like disease. It is one of the most closely related species to the complex. Using as a proxy for the - common ancestor, we asked whether introducing the -specific gene pair into affects the course of experimental infection. Expression of these genes resulted in the production of an adenosine-linked lipid species, known as 1-tuberculosinyladenosine (1-TbAd), but did not alter growth under standard conditions. Production of 1-TbAd enhanced growth of under acidic conditions through a bacterial cell-intrinsic mechanism independent of controlling pH in the bulk extracellular and intracellular spaces. Production of 1-TbAd led to greater burden of in the lungs of C57BL/6 mice during the first 24 h after infection, and infections of alveolar macrophages recapitulated this phenotype within the same time frame. However, in long-term infections, production of 1-TbAd resulted in impaired bacterial survival in both C57BL/6 mice and mice. We have demonstrated that is a valid surrogate of to study virulence factors acquired by the latter organism, yet shown the challenge inherent to studying the complex evolution of mycobacterial pathogenicity with isolated gene complementation. This work sheds light on the role of the lipid 1-tuberculosinyladenosine in the evolution of an environmental ancestor to On a larger scale, it reinforces the importance of horizontal gene transfer in bacterial evolution and examines novel models and methods to provide a better understanding of the subtle effects of individual -specific virulence factors in infection settings that are relevant to the pathogen.