Identification of Listeria monocytogenes Genes Contributing to Oxidative Stress Resistance under Conditions Relevant to Host Infection.

The Gram-positive bacterium survives in environments ranging from the soil to the cytosol of infected host cells. Key to intracellular survival is the activation of PrfA, a transcriptional regulator that is required for the expression of multiple bacterial virulence factors. Mutations that constitutively activate ( mutations) result in high-level expression of multiple bacterial virulence factors as well as the physiological adaptation of for optimal replication within host cells. Here, we demonstrate that mutants exhibit significantly enhanced resistance to oxidative stress in comparison to that of wild-type strains. Transposon mutagenesis of strains resulted in the identification of three novel gene targets required for full oxidative stress resistance only in the context of PrfA activation. One gene, , predicted to encode an uncharacterized protein, and two additional genes known as and , encoding a cyclic di-AMP binding protein and a 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase, respectively, contribute to the enhanced oxidative stress resistance of strains while exhibiting no significant contribution in wild-type Transposon inactivation of and in a background led to reduced virulence in the liver of infected mice. These results indicate that calls upon specific bacterial factors for stress resistance in the context of PrfA activation and thus under conditions favorable for bacterial replication within infected mammalian cells.