The ZnuABC operon is important for Yersinia ruckeri infections of rainbow trout, Oncorhynchus mykiss (Walbaum).

Signature-tagged mutagenesis was used to identify genes essential for survival of Yersinia ruckeri in its natural host, rainbow trout, Oncorhynchus mykiss. A mini-Tn5-Km2 signature-tagged mutant, C6-1, was missing from rainbow trout kidney at 7 days after an immersion challenge. The transposon insertion in C6-1 was in a homologue of the znuA gene of Escherichia coli that encodes ZnuA, a zinc-binding periplasmic protein of the high-affinity zinc transporter ZnuABC. Further sequencing of the C6-1 locus in Y. ruckeri identified homologues of two other genes: znuB, encoding a putative inner membrane permease, and znuC, encoding a putative ATPase. When present on a low-copy plasmid, the znuABC locus of Y. ruckeri fully restored growth of a zinc transport-deficient Delta znuABC mutant of E. coli. Unlike Delta znuABC mutants of E. coli and Salmonella typhimurium, the Delta znuABC mutant of Y. ruckeri did not demonstrate significantly slower growth in zinc-deficient M9 minimal medium or in Luria-Bertani (LB) medium supplemented with the metal chelators EDTA and tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN). In LB medium, the znuA::lacZ and znuCB::lacZ transcriptional fusions of Y. ruckeri were derepressed by addition of EDTA and TPEN and were repressed by addition of zinc and manganese. In a competitive challenge by immersion, the Delta znuABC mutant was unable to compete with the parental strain and survived poorly in rainbow trout kidney, indicating that the ZnuABC transporter has a role in establishing and maintaining a rainbow trout infection by Y. ruckeri.