The Response of Acinetobacter baumannii to Zinc Starvation.

Zinc (Zn) is an essential metal that vertebrates sequester from pathogens to protect against infection. Investigating the opportunistic pathogen Acinetobacter baumannii's response to Zn starvation, we identified a putative Zn metallochaperone, ZigA, which binds Zn and is required for bacterial growth under Zn-limiting conditions and for disseminated infection in mice. ZigA is encoded adjacent to the histidine (His) utilization (Hut) system. The His ammonia-lyase HutH binds Zn very tightly only in the presence of high His and makes Zn bioavailable through His catabolism. The released Zn enables A. baumannii to combat host-imposed Zn starvation. These results demonstrate that A. baumannii employs several mechanisms to ensure bioavailability of Zn during infection, with ZigA functioning predominately during Zn starvation, but HutH operating in both Zn-deplete and -replete conditions to mobilize a labile His-Zn pool.