The Role of c-di-AMP in Listeria monocytogenes

L. monocytogenes is a Gram-positive intracellular pathogen that can cause serious disease, like septicemia and meningitis. It is detected in the cytosol by the innate immune system by sensing pathogen ligands. c-di-AMP has recently been shown to be one of them, inducing an interferon response. L. monocytogenes produces this molecule with the DacA protein and secretes it in the host cell cytosol upon infection. A dacA mutant shows a growth defect indicating an important role for c-di-AMP. To get insights into the role of c-di-AMP this study proposes a forward genetic screen on a dacA mutant to find transposon insertions rescuing growth. The screening of 10 thousands mutants led us to find two insertions. A transposon insertion in a gene involved in DNA metabolism partially rescues growth in broth and intracellular culture. A second transposon insertion in a gene involved in energy metabolism was found to partially rescue intracellular growth only.