A number of bacterial pathogens require the ZnuABC Zinc (Zn2+) transporter and/or a second Zn2+ transport system to overcome Zn2+ sequestration by mammalian hosts. Previously we have shown that in addition to ZnuABC, Yersinia pestis possesses a second Zn2+ transporter that involves components of the yersiniabactin (Ybt), siderophore-dependent iron transport system. Synthesis of the Ybt siderophore and YbtX, a member of the major facilitator superfamily, are both critical components of the second Zn2+ transport system. Here we demonstrate that a ybtX znu double mutant is essentially avirulent in mouse models of bubonic and pneumonic plague while a ybtX mutant retains high virulence in both plague models. While sequestration of host Zn is a key nutritional immunity factor, excess Zn appears to have a significant antimicrobial role in controlling intracellular bacterial survival. Here, we demonstrate that ZntA, a Zn2+ exporter, plays a role in resistance to Zn toxicity in vitro, but that a zntA zur double mutant retains high virulence in both pneumonic and bubonic plague models and survival in macrophages. We also confirm that Ybt does not directly bind Zn2+in vitro under the conditions tested. However, we detect a significant increase in Zn2+-binding ability of filtered supernatants from a Ybt+ strain compared to those from a strain unable to produce the siderophore, supporting our previously published data that Ybt biosynthetic genes are involved in the production of a secreted Zn-binding molecule (zincophore). Our data suggest that Ybt or a modified Ybt participate in or promote Zn-binding activity in culture supernatants and is involved in Zn acquisition in Y. pestis.
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This work was supported by Public Health Services Grant R01 AI33481 from the US National Institutes of Health and by startup funds from the University of Kentucky (to S.G.-T.). M.B.L. and T.T.V. were supported by Public Health Services grant R21 AI119557 from the US National Institutes of Health.
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Bobrov, Alexander G.; Kirillina, Olga; Fosso, Marina Y.; Fetherston, Jacqueline D.; Miller, M. Clarke; VanCleave, Tiva T.; Burlison, Joseph A.; Arnold, William K.; Lawrenz, Matthew B.; Garneau-Tsodikova, Sylvie; and Perry, Robert D., "Zinc Transporters YbtX and ZnuABC Are Required for the Virulence of Yersinia pestis in Bubonic and Pneumonic Plague in Mice" (2017). Microbiology, Immunology, and Molecular Genetics Faculty Publications. 139.