Bacterial strains and growth conditions L. monocytogenes EGDe (BUG1600, ATCC BAA-679), L. monocytogenes isogenic mutant DpgdA (BUG2288, [25] ) and L. monocytogenes DpgdA complemented strain (BUG2382) were grown in brain heart infusion (BHI, Oxoid), aerobically at 37uC and 200 rpm.