PLEIOTROPIC EFFECTS OF A YERSINIA-PESTIS FUR MUTATION

A Yersinia pestis fur mutation was constructed by insertionally disrupting the fur open reading frame. Analysis of a Fur-regulated beta-galactosidase reporter gene revealed a loss of iron regulation as a result of the fur mutation. trans complementation with the cloned Y. pestis fur gene restored iron regulation. The expression of most iron-regulated proteins was also deregulated by this mutation; however, a number of iron-repressible and two iron-inducible polypeptides retained normal regulation. Mutations in fur or hmsH, a gene encoding an 86-kDa surface protein required for hemin storage, increased the sensitivity of Y. pestis cells to the bacteriocin pesticin. Interestingly, the Y. pestis fur mutant lost temperature control of hemin storage; however, expression of the HmsH polypeptide was not deregulated. When growth with excess iron, a Y. pestis fur mutant possessing the 102-kb pigmentation locus exhibited severe growth inhibition and a dramatic increase in the number of spontaneous nonpigmented chromosomal deletion mutants present at late log phase. These results suggest that the Fur protein of Y. pestis is an important global regulator and that a separate Fur-independent iron regulatory system may exist.