In situ studies on N2 fixation using the acetylene reduction technique.

Stewart, W. D. P.; Fitzgerald, George P.; Burris, R. H.

doi:10.1073/pnas.58.5.2071

Cited by 824 publications

(320 citation statements)

References 6 publications

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“…Nitrogenase activity (NA) was measured by acetylene−ethylene reduction as− say (Stewart et al 1967) in 100 mL glass flasks after 90 min incubation. Ethylene in the samples was quantified with a gas chromatograph and nitrogenase activity was expressed in nmol/h C 2 H 4 per g fresh biomass.…”

Section: Ecophysiological Parameters Of Nostoc Communementioning

confidence: 99%

Impact of warming on Nostoc colonies (Cyanobacteria) in a wet hummock meadow, Spitsbergen

Elster¹,

Kvíderová²,

Hájek³

et al. 2012

Polish Polar Research

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Abstract:In order to simulate the warming effects on Arctic wetlands, three passive open−top chambers (OTCs) and three control cage−like structures (CCSs) equipped with soil temperature and soil volumetric water content (VWC) probes for continuous micro− climatic measurements were installed in a wet hummock meadow, Petuniabukta, Bille− fjorden, central Spitsbergen, in 2009. The warming effects on primary productivity were investigated during summer seasons 2009 and 2010 in cyanobacterial colonies of Nostoc commune s.l., which plays an important role in the local carbon and nitrogen cycles. The microclimatic data indicated that the effect of OTCs was dependent on microtopography. During winter, two short−term snow−thaw episodes occurred, so that liquid water was available for the Nostoc communities. Because of the warming, the OTC hummock bases remained unfrozen three weeks longer in comparison to the CCSs and, in spring, the OTC hummock tops and bases exceeded 0°C several days earlier than CCS ones. Mean summer temperature differences were 1.6°C in OTC and CCS hummock tops, and 0.3°C in the OTC and CCS hummock bases. The hummock tops were drier than their bases; however the VWC difference between the OTCs and CCSs was small. Due to the only minor differ− ences in the microclimate of OTC and CCS hummock bases, where the Nostoc colonies were located, no differences in ecophysiological characteristics of Nostoc colonies ex− pressed as photochemistry parameters and nitrogenase activities were detected after two years exposition. Long−term monitoring of Nostoc ecophysiology in a manipulated envi− ronment is necessary for understanding their development under climate warming.

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Section: Ecophysiological Parameters Of Nostoc Communementioning

confidence: 99%

Impact of warming on Nostoc colonies (Cyanobacteria) in a wet hummock meadow, Spitsbergen

Elster¹,

Kvíderová²,

Hájek³

et al. 2012

Polish Polar Research

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“…Nitrogen fixation rates were estimated using the acetylene reduction assay (31). Rates were linear during the assay period of 30 min.…”

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confidence: 99%

Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

Bellenger

Wichard

Kraepiel

2008

Appl Environ Microbiol

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Vanadium is a cofactor in the alternative V-nitrogenase that is expressed by some N 2 -fixing bacteria when Mo is not available. We investigated the V requirements, the kinetics of V uptake, and the production of catechol compounds across a range of concentrations of vanadium in diazotrophic cultures of the soil bacterium Azotobacter vinelandii. In strain CA11.70, a mutant that expresses only the V-nitrogenase, V concentrations in the medium between 10 ؊8 and 10 ؊6 M sustain maximum growth rates; they are limiting below this range and toxic above. A. vinelandii excretes in its growth medium micromolar concentrations of the catechol siderophores azotochelin and protochelin, which bind the vanadate oxoanion. The production of catechols increases when V concentrations become toxic. Short-term uptake experiments with the radioactive isotope 49 V show that bacteria take up the V-catechol complexes through a regulated transport system(s), which shuts down at high V concentrations. The modulation of the excretion of catechols and of the uptake of the V-catechol complexes allows A. vinelandii to precisely manage its V homeostasis over a range of V concentrations, from limiting to toxic.

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“…Heterocyst frequency was calculated as percentage of total cells by light microscopic observations after 96 h of incubation in different media. Acetylene reduction assay was used to measure nitrogenase activity 7 .…”

Section: Growth Heterocyst Frequency and Nitrogenase Activitymentioning

confidence: 99%

Isolation and characterization of a Mastigocladus species capable of growth, N2-fixation and N-assimilation at elevated temperature

et al. 2007

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A Mastigocladus species was isolated from the hot spring of Jakrem (Meghalaya) India. Uptake and utilization of nitrate, nitrite, ammonium and amino acids (glutamine, asparagine, arginine, alanine) were studied in this cyanobacterium grown at different temperatures (25ºC, 45ºC). There was 2-3 fold increase in the heterocyst formation and nitrogenase activity in N-free medium at higher temperature (45ºC). Growth and uptake and assimilation of various nitrogen sources were also 2-3 fold higher at 45ºC indicating that it is a thermophile. The extent of induction and repression of nitrate uptake by NO 3¯ and NH 4 + , respectively, differed from that of nitrite. It appeared that Mastigocladus had two independent nitrate/nitrite transport systems. Nitrate reductase and nitrite reductase activitiy was not NO 3¯-inducible and ammonium or amino acids caused only partial repression. Presence of various amino acids in the media partially repressed glutamine synthetase activity. Ammonium (methylammonium) and amino acid uptake showed a biphasic pattern, was energy-dependent and the induction of uptake required de novo protein synthesis. Ammonium transport was substrate (NH 4 + ) -repressible, while the amino acid uptake was substrate inducible. When grown at 25ºC, the cyanobacterium formed maximum akinetes that remained viable upto 5 years under dry conditions.

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In situ studies on N2 fixation using the acetylene reduction technique.

Cited by 824 publications

References 6 publications

Impact of warming on Nostoc colonies (Cyanobacteria) in a wet hummock meadow, Spitsbergen

Impact of warming on Nostoc colonies (Cyanobacteria) in a wet hummock meadow, Spitsbergen

Vanadium Requirements and Uptake Kinetics in the Dinitrogen-Fixing Bacterium Azotobacter vinelandii

Isolation and characterization of a Mastigocladus species capable of growth, N2-fixation and N-assimilation at elevated temperature

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