Insights into Membrane Association of Klebsiella pneumoniae NifL under Nitrogen-Fixing Conditions from Mutational Analysis

ABSTRACT The nitrogen-fixing symbiont of alfalfa, Sinorhizobium meliloti, is able to use myo-inositol as the sole carbon source. Putative inositol catabolism genes (iolA and iolRCDEB) have been identified in the S. meliloti genome based on their similarities with the Bacillus subtilis iol genes. In this study, functional mutational analysis revealed that the iolA and iolCDEB genes are required for growth not only with the myo-isomer but also for growth with scyllo- and d-chiro-inositol as the sole carbon source. An additional, hypothetical dehydrogenase of the IdhA/MocA/GFO family encoded by the smc01163 gene was found to be essential for growth with scyllo-inositol, whereas the idhA-encoded myo-inositol dehydrogenase was responsible for the oxidation of d-chiro-inositol. The putative regulatory iolR gene, located upstream of iolCDEB, encodes a repressor of the iol genes, negatively regulating the activity of the myo- and the scyllo-inositol dehydrogenases. Mutants with insertions in the iolA, smc01163, and individual iolRCDE genes could not compete against the wild type in a nodule occupancy assay on alfalfa plants. Thus, a functional inositol catabolic pathway and its proper regulation are important nutritional or signaling factors in the S. meliloti-alfalfa symbiosis.

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Mutational analysis of the Klebsiella pneumoniae nitrogenase promoter: sequences essential for positive control by nifA and ntrC (glnG) products.

Journal of Bacteriology ◽

10.1128/jb.161.3.868-874.1985 ◽

1985 ◽

Vol 161 (3) ◽

pp. 868-874 ◽

Cited By ~ 24

Author(s):

D W Ow ◽

Y Xiong ◽

Q Gu ◽

S C Shen

Keyword(s):

Klebsiella Pneumoniae ◽

Mutational Analysis ◽

Positive Control ◽

Promoter Sequences

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Plasmids Formed in Nitrogen-fixing Escherichia coli-Klebsiella pneumoniae Hybrids

Journal of General Microbiology ◽

10.1099/00221287-80-1-241 ◽

1974 ◽

Vol 80 (1) ◽

pp. 241-251 ◽

Cited By ~ 17

Author(s):

F. C. Cannon ◽

R. A. Dixon ◽

J. R. Postgate ◽

S. B. Primrose

Keyword(s):

Escherichia Coli ◽

Klebsiella Pneumoniae ◽

Nitrogen Fixing

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Purification and partial characterization of a pyruvate oxidoreductase from the photosynthetic bacterium Rhodospirillum rubrum grown under nitrogen-fixing conditions

Biochemical Journal ◽

10.1042/bj2790155 ◽

1991 ◽

Vol 279 (1) ◽

pp. 155-158 ◽

Cited By ~ 37

Author(s):

E Brostedt ◽

S Nordlund

Keyword(s):

Klebsiella Pneumoniae ◽

Rhodospirillum Rubrum ◽

Nitrogenase Activity ◽

Photosynthetic Bacterium ◽

Molecular Properties ◽

Partial Characterization ◽

Nitrogen Fixing ◽

Pyruvate Oxidoreductase

A pyruvate oxidoreductase with the capacity to support pyruvate-dependent nitrogenase activity in vitro has been purified from the photosynthetic bacterium Rhodospirillum rubrum. The enzyme requires CoA for activity and is irreversibly inactivated by oxygen. The molecular properties and Km values for the substrates have been studied. In supporting nitrogenase activity addition of ferredoxin is required. Overall the enzyme is similar to the nif-specific pyruvate: flavodoxin oxidoreductase purified from Klebsiella pneumoniae.

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Nitrogen Fixation in Wheat Provided by Klebsiella pneumoniae 342

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2004.17.10.1078 ◽

2004 ◽

Vol 17 (10) ◽

pp. 1078-1085 ◽

Cited By ~ 165

Author(s):

A. Leonardo Iniguez ◽

Yuemei Dong ◽

Eric W. Triplett

Keyword(s):

Nitrogen Fixation ◽

Klebsiella Pneumoniae ◽

Nitrogen Deficiency ◽

Triticum Aestivum L ◽

Nitrogen Fixing ◽

Root Cortex ◽

Wheat Roots ◽

Total N ◽

Plant Nitrogen ◽

Deficiency Symptoms

In this report, all of the criteria necessary for the demonstration of nitrogen fixation in wheat (Triticum aestivum L.), the world's most important crop, are shown upon inoculation with a nitrogen-fixing bacterium, Klebsiella pneumoniae 342 (Kp342). Kp342 relieved nitrogen (N) deficiency symptoms and increased total N and N concentration in the plant. Nitrogen fixation was confirmed by 15N isotope dilution in the plant tissue and in a plant product, chlorophyll. All of these observations were in contrast to uninoculated plants, plants inoculated with a nitrogen-fixing mutant of Kp342, and plants inoculated with dead Kp342 cells. Nitrogenase reductase was produced by Kp342 in the intercellular space of the root cortex. Wild-type Kp342 and the nifH mutant colonized the interior of wheat roots in equal numbers on a fresh weight basis. The nitrogen fixation phenotype described here was specific to cv. Trenton. Inoculation of cvs. Russ or Stoa with Kp342 resulted in no relief of nitrogen deficiency symptoms.

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