ZurR was previously thought to be involved in listerial tolerance of the biological detergent bile, which affects

membrane integrity and macromolecule stability in bacterial cells (Begley et al., 2002, 2005). That study screened L. monocytogenes transposon mutants for a decreased ability to survive in bile in vitro. However, in the current study, we have shown that zurR is not necessary for L. monocytogenes to withstand the toxic effects of bile (Fig. 2b). Indeed, it appears that the clean deletion mutant of zurR is actually marginally more bile tolerant than the wild type. In contrast, a reconstructed pORI19 plasmid integration mutant (Fig. 2b) in zurR was significantly reduced in bile click here tolerance reflecting the reduced tolerance of the transposon

mutant reported previously (Begley et al., 2002). It is likely that the phenotype of the insertional mutants in bile results either from a polar effect upon downstream genes or that the mutations have led to partially functional membrane proteins that MDV3100 in vivo impact upon survival in bile. In the current study, the virulence of ΔzurR was significantly reduced in the murine model of infection (Fig. 3). The work demonstrates the importance of zinc homeostasis for in vivo viability and virulence potential in L. monocytogenes. Similarly, the metalloregulators Fur and PerR have also been shown to play subtle but significant roles in successful L. monocytogenes next infection (Rea et al., 2004). Interestingly, in Salmonella enterica and Staphylococcus aureus, deletion of zurR did not result in any attenuation of the strain (Lindsay & Foster, 2001; Campoy et al., 2002). However, the regulator is absolutely required for infection of plants by Xanthomonas species (Tang et al., 2005; Yang et al., 2007). The current study provides a platform to facilitate further work to dissect the precise components required for zinc uptake by L. monocytogenes during infection. In this study, we identified 11 genes distributed over five loci as being putatively ZurR regulated using a bioinformatic approach (Fig. 4a). Briefly, the L. monocytogenes EGDe genome (Glaser et al., 2001) was scanned

for homologs of genes that have been shown to be regulated by Zur in B. subtilis (ycdH, ycdI, yceA, yckA), E. coli (znuA, znuB, znuC), and S. aureus (mreA, mreB). Loci showing significant homology were then examined for the possession of a putative B. subtilis Zur box (TCGTAATnATTACGA) (Gaballa & Helmann, 2002) using the genome web server Listilist (http://genolist.Pasteur.fr/Listilist/). Putative zur boxes were limited to 500 bp upstream of the start codon of the identified gene (Fig. 4b). By utilizing this technique, there is a possibility that we have excluded genes regulated by zurR, which are unique to L. monocytogenes, those that are regulated in the absence of the consensus sequence and those that may be regulated indirectly by zurR. This approach identified the following L.