Cytoplasmic Copper Detoxification in Salmonella Can Contribute to SodC Metalation but Is Dispensable during Systemic Infection.

serovar Typhimurium is a leading cause of foodborne disease worldwide. Severe infections result from the ability of Typhimurium to survive within host immune cells, despite being exposed to various host antimicrobial factors. SodCI, a copper-zinc-cofactored superoxide dismutase, is required to defend against phagocytic superoxide. SodCII, an additional periplasmic superoxide dismutase, although produced during infection, does not function in the host. Previous studies suggested that CueP, a periplasmic copper binding protein, facilitates acquisition of copper by SodCII. CopA and GolT, both inner membrane ATPases that pump copper from the cytoplasm to the periplasm, are a source of copper for CueP. Using SOD assays, we found that SodCI can also utilize CueP to acquire copper. However, both SodCI and SodCII have a significant fraction of activity independent of CueP and cytoplasmic copper export. We utilized a series of mouse competition assays to address the role of CueP-mediated SodC activation. A triple mutant was equally as competitive as the wild type, suggesting that sufficient SodCI is active to defend against phagocytic superoxide independent of CueP and cytoplasmic copper export. We also confirmed that a strain containing a modified SodCII, which is capable of complementing a deletion, was fully virulent in a background competed against the wild type. These competitions also address the potential impact of cytoplasmic copper toxicity within the phagosome. Our data suggest that does not encounter inhibitory concentrations of copper during systemic infection. is a leading cause of gastrointestinal disease worldwide. In severe cases, can cause life-threatening systemic infections, particularly in very young children, the elderly, or people who are immunocompromised. To cause disease, must survive the hostile environment inside host immune cells, a location in which most bacteria are killed. Our work examines how one particular metal, copper, is acquired by to activate a protein important for survival within immune cells. At high levels, copper itself can inhibit Using a strain of that cannot detoxify intracellular copper, we also addressed the role of copper as an antimicrobial agent.