Open AccessBradyrhizobium japonicumNnrR, a Denitrification Regulator, Expands the FixLJ-FixK2Regulatory Cascade
Author(s) -
Socorro Mesa,
Eulogio J. Bedmar,
Astrid Chanfon,
Hauke Hennecke,
HansMartin Fischer
Publication year - 2003
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.185.13.3978-3982.2003
Subject(s) - bradyrhizobium japonicum , biology , nitrite reductase , nitrate reductase , mutant , nitrite , denitrification , nitric oxide , nitrate , biochemistry , regulator , bradyrhizobium , gene , microbiology and biotechnology , rhizobium , rhizobiaceae , genetics , enzyme , symbiosis , bacteria , chemistry , ecology , organic chemistry , nitrogen , endocrinology
In Bradyrhizobium japonicum, a gene named nnrR was identified which encodes a protein with high similarity to FNR/CRP-type transcriptional regulators. Mutant strains carrying an nnrR null mutation were unable to grow anaerobically in the presence of nitrate or nitrite, and they lacked both nitrate and nitrite reductase activities. Anaerobic activation of an nnrR'-'lacZ fusion required FixLJ and FixK(2). In turn, N oxide-mediated induction of nir and nor genes encoding nitrite and nitric oxide reductase, respectively, depended on NnrR. Thus, NnrR expands the FixLJ-FixK(2) regulatory cascade by an additional control level which integrates the N oxide signal required for maximal induction of the denitrification genes.