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The purMN Genes of Rhizobium leguminosarum and a Superficial Link with Siderophore Production

February 2000 , Volume 13 , Number  2
Pages  228 - 231

James B. Stevens , 1 Nicola G. de Luca , 1 John E. Beringer , 2 John P. Ringer , 1 Kay H. Yeoman , 1 and Andrew W. B. Johnston 1

1School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K.; 2School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, U.K.

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Accepted 29 October 1999.

We isolated a mutant of R. leguminosarum initially on the basis of reduced production of the siderophore vicibactin on chrome azurol sulfonate (CAS)/agar indicator plates. The mutation was in the purMN operon and the mutant was shown to be an adenine auxotroph and defective for nodulation of peas. The siderophore defect appears to be trivial, being due to diminished growth of the auxotroph on agar-based minimal medium, which contains unknown contaminant(s) that allow it grow poorly. Transcriptional fusions showed that purMN was transcribed at relatively high levels in media containing purines. Expression was enhanced, approximately twofold, if purines were omitted.

Additional keywords: N2 fixation, purine auxotrophy.

© 2000 The American Phytopathological Society