Isolation of an Asm− mutant of Rhizobium japonicum defective in symbiotic N2-fixation
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Although mutant CJ9 induced nitrogenase activity in an ‘in vitro’ assay system under microaerobic conditions, it failed to fix nitrogen (acetylene reduction) in soybean root nodules and constitute a new Asm − mutant class in Rhizobium spp.Abstract:
A mutant strain of Rhizobium japonicum (CJ9) unable to assimilate ammonium (Asm − ) was isolated following mutagenesis with N -methyl N -nitro-nitrosoguanidine (NTG). Glutamate synthase activity was not detectable in cell-free extracts of the mutant strain in contrast to the wild type and revertant strains. Although mutant CJ9 induced nitrogenase activity in an ‘in vitro’ assay system under microaerobic conditions, it failed to fix nitrogen (acetylene reduction) in soybean root nodules. These properties of mutant CJ9 constitute a new Asm − mutant class in Rhizobium spp.read more
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Journal ArticleDOI
Key role of bacterial NH(4)(+) metabolism in Rhizobium-plant symbiosis.
TL;DR: The regulatory circuitry responsible for the downregulation of bacterial genes involved in NH4+ assimilation occurring early during nodule invasion is described, which is a key and necessary step for the differentiation of N2-fixing bacteroids and for the development of efficient nodules.
Book ChapterDOI
Carbon and nitrogen metabolism in Rhizobium
Philip S. Poole,David Allaway +1 more
TL;DR: One of the paradigms of symbiotic nitrogen fixation has been that bacteroids reduce N2 to ammonium and secrete it without assimilation into amino acids, but this has recently been challenged by work with soybeans showing that only alanine is excreted in 15N2 labelling experiments.
Journal ArticleDOI
Ammonium assimilation in Rhizobium phaseoli by the glutamine synthetase-glutamate synthase pathway.
Alejandra Bravo,J. Mora +1 more
TL;DR: Evidence from in vitro and in vivo studies showed that in Rhizobium phaseoli ammonium is assimilated by the glutamine synthetase (GS)-glutamate synthase NADPH pathway, and GSII was inactivated after the addition of high ammonium concentrations, when the 2-oxoglutarate/glutamine ratio decreased rapidly.
Journal ArticleDOI
Key roles of microsymbiont amino acid metabolism in rhizobia-legume interactions
TL;DR: This review summarizes past findings and current research directions in rhizobial amino acid metabolism and evaluates the genetic, biochemical and genome expression studies from which these are derived and the symbiotic roles of individual amino acids in different plant-rhizobia combinations.
Journal ArticleDOI
Carbon metabolism in Bradyrhizobium japonicum bacteroids
TL;DR: Other adaptive pathways that may be employed by these organisms while in symbiosis are considered, including a poly-β-hydroxy-butyrate shunt, a malate-aspartate shuttle, and a modified dicarboxylic acid cycle.
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