Some properties of a Klebsiella pneumoniae ammonium transport negative mutant (Amt?)

Castorph, Helga; Kleiner, Diethelm

doi:10.1007/bf00402008

Cited by 38 publications

(31 citation statements)

References 18 publications

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“…The amtB gene has been implicated in the release of ammonium previously in other bacteria. Castorph and Kleiner reported that ammonium transport mutants (Amt Ϫ ) excreted ammonium in Klebsiella pneumonia (48). Meletzus et al isolated amtB mutants from A. vinelandii and showed that amtB mutants could grow on limiting ammonium but were unable to transport methylammonium (37).…”

Section: Discussionmentioning

confidence: 99%

Gene Deletions Resulting in Increased Nitrogen Release by Azotobacter vinelandii: Application of a Novel Nitrogen Biosensor

Barney

Eberhart

Ohlert

et al. 2015

Appl Environ Microbiol

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Azotobacter vinelandii is a widely studied model diazotrophic (nitrogen-fixing) bacterium and also an obligate aerobe, differentiating it from many other diazotrophs that require environments low in oxygen for the function of the nitrogenase. As a freeliving bacterium, A. vinelandii has evolved enzymes and transporters to minimize the loss of fixed nitrogen to the surrounding environment. In this study, we pursued efforts to target specific enzymes and further developed screens to identify individual colonies of A. vinelandii producing elevated levels of extracellular nitrogen. Targeted deletions were done to convert urea into a terminal product by disrupting the urease genes that influence the ability of A. vinelandii to recycle the urea nitrogen within the cell. Construction of a nitrogen biosensor strain was done to rapidly screen several thousand colonies disrupted by transposon insertional mutagenesis to identify strains with increased extracellular nitrogen production. Several disruptions were identified in the ammonium transporter gene amtB that resulted in the production of sufficient levels of extracellular nitrogen to support the growth of the biosensor strain. Further studies substituting the biosensor strain with the green alga Chlorella sorokiniana confirmed that levels of nitrogen produced were sufficient to support the growth of this organism when the medium was supplemented with sufficient sucrose to support the growth of the A. vinelandii in coculture. The nature and quantities of nitrogen released by urease and amtB disruptions were further compared to strains reported in previous efforts that altered the nifLA regulatory system to produce elevated levels of ammonium. These results reveal alternative approaches that can be used in various combinations to yield new strains that might have further application in biofertilizer schemes. N utrient requirements are directly linked to biomass production, and any potential increased improvement in the scale of biomass yield will necessitate a proportional increase in the demand for essential nutrients. For all photosynthetic organisms (photoautotrophs such as land plants, algae, and cyanobacteria) with requisite light energy and water, nitrogen is the most limiting and expensive nutrient input for aquaculture and agricultural production alike (1). A majority of our current nitrogen fertilizer production is tied to the burning of fossil fuels to generate ammonia from molecular nitrogen (N 2 gas) through the Haber-Bosch process, which accounts for 3 to 5% of world natural gas consumption, or about 1 to 2% of total worldwide energy expenditures (1-3). In developed countries, industrial nitrogen production is accompanied by a huge economic and energetic cost overall (2), while this key nutrient limits agricultural productivity in developing countries, where energy and infrastructure costs prohibit the utilization of the Haber-Bosch process to produce ammonia from atmospheric nitrogen on a large scale.The development of biological approaches to improve biof...

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Section: Discussionmentioning

confidence: 99%

Gene Deletions Resulting in Increased Nitrogen Release by Azotobacter vinelandii: Application of a Novel Nitrogen Biosensor

Barney

Eberhart

Ohlert

et al. 2015

Appl Environ Microbiol

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“…Activities of glutamine synthetase, glutamate dehydrogenase and GOGAT, as well as amino acid and methylammonium transport, extracellular ammonia levels and bacterial protein contents were determined as described [14].…”

Section: Methodsmentioning

confidence: 99%

Characterization of the gltF gene product of Escherichia coli

Grassl

1999

FEMS Microbiology Letters

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The glt operon of Escherichia coli comprises the structural genes for the glutamate synthase subunits (gltB and gltD) and gltF, whose product was previously suggested to have regulatory functions. The A/T-rich region between gltD and gltF contains a weak promoter and a translation initiation site for gltF. The GltF protein is preceded by a signal peptide, which is cleaved off during export into the periplasmic space. A gltF : :Km R insertion mutant was constructed and shown here to have no detectable phenotype with respect to amino acid utilization or ammonium transport. Thus, GltF is apparently not involved in regulation of nitrogen catabolism. ß

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“…An AmtmUtant of Klebsiella pneumoniae which failed to grow on 1 mM NH4+ was also deficient in glutamine synthetase (4), suggesting introduction of an Ntr mutation. Servin-Gonzalez et al (26) have recently reported the isolation of methylammoniumi-resistant mutants of E. coli.…”

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confidence: 99%

Isolation of an ammonium or methylammonium ion transport mutant of Escherichia coli and complementation by the cloned gene

et al. 1989

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During nitrogen-limited growth, Escherichia coli expresses a specific ammonium or methylammonium ion transport system (Amt). Strains carrying defects in Amt have been isolated following TnlO transposon mutagenesis. These mutants have <10% of the transport activity of the parental strain. Glutamate, glutamine, arginine, or high levels (20 mM) of ammonium will serve as the sole nitrogen source for growth of these strains, and glutamine synthetase is normally expressed and repressed by the nitrogen regulatory (Ntr)

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Some properties of a Klebsiella pneumoniae ammonium transport negative mutant (Amt?)

Cited by 38 publications

References 18 publications

Gene Deletions Resulting in Increased Nitrogen Release by Azotobacter vinelandii: Application of a Novel Nitrogen Biosensor

Gene Deletions Resulting in Increased Nitrogen Release by Azotobacter vinelandii: Application of a Novel Nitrogen Biosensor

Characterization of the gltF gene product of Escherichia coli

Isolation of an ammonium or methylammonium ion transport mutant of Escherichia coli and complementation by the cloned gene

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