Contributions of [sigma] super(B) and PrfA to Listeria monocytogenes salt stress under food relevant conditions

Listeria monocytogenes is well known to survive and grow under several stress conditions, including salt stress, which is important for growth in certain foods as well as for host infection. To characterize the contributions. to salt stress response, of transcriptional regulators important for stress response and virulence, we analyzed three L. monocytogenes parent strains and isogenic mutants, representing different serotypes and lineages, for their ability to grow, at 25[degrees]C, in BHI with 1.9 M NaCI. With regard to growth rate, only the lineage IV strain presented a significant difference between the parent strain and both of its respective mutants lacking prfA. Intestinal epithelial cell invasion assay and hemolytic activity assays showed a significant role for delta [subB] in the former and for PrfA in the latter. Moreover, we show that the delta [subB] regulon of a L. monocytogenes lineage I strain challenged with salt shock includes salt stress-specific as well as previously unidentified delta [subB] up-regulated genes.