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.
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.
Yeoman
Kay H
KH
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
Wisniewski-Dye
Florence
F
John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK2.
Timony
Christopher
C
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
Stevens
James B
JB
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
deLuca
Nicola G
NG
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
Downie
J Allan
JA
John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK2.
Johnston
Andrew W B
AWB
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D010802:Phylogeny; D011544:Pseudogenes; D011991:Receptors, Virus / Q000235:genetics*; D016961:Rhizobium leguminosarum / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D013045:Species Specificity
D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C050900:FhuA protein, E coli; D011991:Receptors, Virus; D009584:Nitrogen