Uracil Debases Pathogenic but Not Commensal Bacteria

The metazoan gut harbors microbial communities on its mucosal surfaces, yet the mechanisms by which gut immunity tolerates symbiotic and commensal bacteria while eliminating pathogens is insufficiently understood. In a recent Cell paper, Lee et al. (2013) show that bacterial uracil, not secreted by commensal bacteria, triggers dual oxidase-dependent immunity.