Analysis of the Rhizobium leguminosarum siderophore-uptake gene fhuA: Differential expression in free-living bacteria and nitrogen-fixing bacteroids and distribution of an fhuA pseudogene in different strains

Kay H. Yeoman, Florence Wisniewski-Dye, Christopher Timony, James B. Stevens, Nicola G. DeLuca, J. Allan Downie, Andrew W. B. Johnston

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28 Citations (Scopus)


A mutation was isolated in the Rhizobium leguminosarum gene fhuA, which appears to specify the outer-membrane receptor for the siderophore vicibactin. The mutant was defective in iron uptake and accumulated the siderophore vicibactin in the extracellular medium. Expression of fhuA was regulated by Fe3+, transcription being higher in iron-depleted cells. Transcription of fhuA was independent of a functional copy of rpol, a neighbouring gene that specifies a putative ECF sigma factor of RNA polymerase and which is involved in siderophore production in Rhizobium. Mutations in fhuA did not detectably affect symbiotic N2 fixation on peas. An fhuA::gus fusion was expressed by bacteria in the meristematic zone of pea nodules but not in mature bacteroids. Some other strains of R. leguminosarum also contain a pseudogene version of fhuA. The sequences of some of these and the 'real' fhuA genes were determined.
Original languageEnglish
Pages (from-to)829-837
Number of pages9
Issue number4
Publication statusPublished - 1 Apr 2000


  • ECF
  • σ factor
  • fhu genes
  • Iron-medicated regulation
  • Pseudogene
  • Rhiozbia
  • Siderophores

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