MntC-Dependent Manganese Transport Is Essential for Oxidative Stress Resistance and Virulence.

is a human pathogen that has developed several approaches to evade the immune system, including a strategy to resist oxidative killing by phagocytes. This resistance is mediated by production of superoxide dismutase (SOD) enzymes which use manganese as a cofactor. encodes two manganese ion transporters, MntABC and MntH, and a possible Nramp family manganese transporter, exemplified by N315 SA1432. Their relative contributions to manganese transport have not been well defined in clinically relevant isolates. For this purpose, insertional inactivation mutations were introduced into , , and SA1432 individually and in combination. was necessary for full resistance to methyl viologen, a compound that generates intracellular free radicals. In contrast, strains with an intact gene had a minimal increase in resistance that was revealed only in strains, and no change was observed upon mutation of SA1432 in strains lacking both and Similarly, MntC alone was required for high cellular SOD activity. In addition, strains were attenuated in a murine sepsis model. To further link these observations to manganese transport, an MntC protein lacking manganese binding activity was designed, expressed, and purified. While circular dichroism experiments demonstrated that the secondary and tertiary structures of this protein were unaltered, a defect in manganese binding was confirmed by isothermal titration calorimetry. Unlike complementation with wild-type , introduction of the manganese-binding defective allele into the chromosome of an strain did not restore resistance to oxidative stress or virulence. Collectively, these results underscore the importance of MntC-dependent manganese transport in oxidative stress resistance and virulence. Work outlined in this report demonstrated that MntC-dependent manganese transport is required for virulence. These study results support the model that MntC-specific antibodies elicited by a vaccine have the potential to disrupt manganese transport and thus abrogate to its virulence.