Genetic and Biochemical Analysis of Mutants Affected in Nitrate Reduction in Rhizobium meliloti
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TLDR
All mutants tested were effective in symbiotic plant tests and had normal nitrogenase activity, indicating that nitrogenase and nitrate reductase do not share the same molybdenum cofactor.Abstract:
Twenty-five mutants unable to utilize nitrate as sole nitrogen source were isolated from Rhizobium meliloti 41. These mutations mapped at four different sites, narA, narB, narC and narD; narB, C and D were located between trp-15 and ade-15 on the chromosome. NarA mutants were affected in assimilatory nitrate reduction but not in‘respiratory’ nitrate reduction and had methyl viologen-coupled nitrate reductase activity. NarB mutants were affected in both assimilatory and ‘respiratory’ nitrate reduction and lacked methyl viologen-coupled nitrate reductase activity. NarC and narD mutants were impaired not only in assimilatory and ‘respiratory’ nitrate reduction but lacked xanthine dehydrogenase activity as well. Acid-treated crude extracts of these two mutant classes were unable to restore NADPH-coupled nitrate reductase activity to the nit-1 mutant of Neurospora crassa, indicating the lack of active molybdenum cofactor. All mutants tested were effective in symbiotic plant tests and had normal nitrogenase activity, indicating that nitrogenase and nitrate reductase do not share the same molybdenum cofactor.read more
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Detecting and characterizing N-acyl-homoserine lactone signal molecules by thin-layer chromatography
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Paul D. Shaw,Gao Ping,Sean L. Daly,C Hung Cha,John E. Cronan,K Enneth L. Rinehart,Stephen K. Farrand +6 more
TL;DR: In this paper, the authors used thin-layer chromatography with detection using Agrobacterium tumefa-ciens harboring lacZ fused to a gene that is regulated by autoinduction.
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Location of nodulation and nitrogen fixation genes on a high molecular weight plasmid of R. meliloti.
TL;DR: R meliloti strain 41 (Rm41) was shown to harbor two indigenous plasmids with molecular weights of 140 Mdal (pRmc41a) and more than 300 Mdal(pRme41b), respectively using a heat-treatment procedure, derivatives of Rm41 defective in nodulation (Nod-) or nitrogen fixation (Fix-) have been readily obtained as discussed by the authors.
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Heme biosynthesis in Rhizobium. Identification of a cloned gene coding for delta-aminolevulinic acid synthetase from Rhizobium meliloti.
TL;DR: A symbiotically important gene system in rhizobial species is the heme biosynthetic pathway and a mutant having reduced levels of delta-aminolevulinic acid synthetase, the first unique enzyme in this pathway, was obtained in Rhizobium meliloti 102F34 by N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis.
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Physical and genetic analysis of a symbiotic region of Rhizobium meliloti: Identification of nodulation genes
TL;DR: The results of this study correlate well with transcription data of nodule-specific expression of plasmid sequences, and are designated as “common” nod genes because mutations in them can be complemented by plasmids derived from different Rhizobium strains.
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