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Regulation of nitrogen metabolism is altered in a glnB mutant strain of Rhizobium leguminosarum
Author(s) -
Amar M.,
Patriarca E. J.,
Manco G.,
Bernard P.,
Riccio A.,
Lamberti A.,
Defez R.,
Laccarino M.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00346.x
Subject(s) - mutant , biology , rhizobium leguminosarum , promoter , rhizobium , gene , rhizobiaceae , sigma factor , strain (injury) , transcription (linguistics) , genetics , biochemistry , gene expression , symbiosis , bacteria , linguistics , philosophy , anatomy
Summary We isolated a Rhizobium leguminosarum mutant strain altered in the glnB gene. This event, which has never been described in the Rhizobiaceae, is rare in comparison to mutants isolated in the contiguous gene, glnA. The glnB mutation removes the glnBA promoter but in vivo does not prevent glnA expression from its own promoter, which is not nitrogen regulated. The glnB mutant strain does not grow on nitrate as a sole nitrogen source and it is Nod + , Fix + . Two –24/–12 promoters, for the glnll and glnBA genes, are constitutively expressed in the glnB mutant, while two –35/–10‐like promoters for glnA and ntrBC are unaffected. We propose that the glnB gene product, the P 11 protein, plays a negative role in the ability of NtrC to activate transcription from its target promoters and a positive role in the mechanism of nitrate utilization.