scholarly journals A Simple in situ Assay to Assess Plant-Associative Bacterial Nitrogenase Activity

2021 ◽  
Vol 12 ◽  
Author(s):  
Timothy L. Haskett ◽  
Hayley E. Knights ◽  
Beatriz Jorrin ◽  
Marta D. Mendes ◽  
Philip S. Poole
Keyword(s):  
Nitrogenase Activity ◽  
Cereal Crops ◽  
N Fixation ◽  
Diazotrophic Bacteria ◽  
Free Living ◽  
Reduction Assay ◽  
Microbe Interactions ◽  
And Function ◽  
In Situ Assay

Assessment of plant-associative bacterial nitrogen (N) fixation is crucial for selection and development of elite diazotrophic inoculants that could be used to supply cereal crops with nitrogen in a sustainable manner. Although diazotrophic bacteria possess diverse oxygen tolerance mechanisms, most require a sub 21% oxygen environment to achieve optimal stability and function of the N-fixing catalyst nitrogenase. Consequently, assessment of N fixation is routinely carried out on “free-living” bacteria grown in the absence of a host plant and such experiments may not accurately divulge activity in the rhizosphere where the availability and forms of nutrients such as carbon and N, which are key regulators of N fixation, may vary widely. Here, we present a modified in situ acetylene reduction assay (ARA), utilizing the model cereal barley as a host to comparatively assess nitrogenase activity in diazotrophic bacteria. The assay is rapid, highly reproducible, applicable to a broad range of diazotrophs, and can be performed with simple equipment commonly found in most laboratories that investigate plant-microbe interactions. Thus, the assay could serve as a first point of order for high-throughput identification of elite plant-associative diazotrophs.

scholarly journals A simple assay for quantification of plant-associative bacterial nitrogen fixation

2021 ◽  
Author(s):  
Timothy L Haskett ◽  
Philip S Poole
Keyword(s):  
Nitrogen Fixation ◽  
Crop Production ◽  
Plant Root ◽  
Cereal Crops ◽  
N Fixation ◽  
In Planta ◽  
Low Oxygen ◽  
Microbe Interactions ◽  
And Function ◽  
Plant Root Systems

AbstractAccurate quantification of plant-associative bacterial nitrogen (N) fixation is crucial for selection and development of elite diazotrophic inoculants that could be used to supply cereal crops with nitrogen in a sustainable manner. Because a low oxygen environment that may not be conducive to plant growth is essential for optimal stability and function of the N-fixing catalyst nitrogenase, quantification of N fixation is routinely carried out on “free-living” bacteria grown in the absence of a host plant. Such experiments may not divulge the true extent of N fixation occurring in the rhizosphere where the availability and forms of nutrients such as carbon and N, which are key regulators of N fixation, may vary widely. Here, we present a modified in planta acetylene reduction assay, utilising the model cereal barley as a host, to quantify associative N fixation by diazotrophic bacteria. The assay is rapid, highly reproducible, applicable to a broad range of diazotrophs, and can be performed with simple equipment commonly found in most laboratories that investigate plant-microbe interactions.ImportanceExploiting “nitrogen-fixing” bacteria that reduce atmospheric dinitrogen into ammonia as inoculants of cereal crops has great potential to alleviate current inputs of environmentally deleterious fertiliser nitrogen and drive more sustainable crop production. Accurately quantifying plant-associative bacterial nitrogen fixation is central to the development of such inoculant bacteria, but most assays fail to adequately reproduce the conditions of plant root systems. In this work, we have validated and optimised a simple in planta assay to accurately quantify N fixation in bacteria occupying the root and surrounding soil of the model cereal barley. This assay represents a benchmark for quantification of plant-associative bacterial N fixation.

Research on Improvement of Nitrogenase Activity of Free-Living Nitrogen-Fixing Bacteria Using DBD Plasma

2013 ◽  
Vol 671-674 ◽  
pp. 2674-2678 ◽  
Author(s):  
Yan Yun Zhu ◽  
Xiao Li Zhu ◽  
Fang She Yang
Keyword(s):  
Rhizosphere Soil ◽  
Barrier Discharge ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Bacterial Strains ◽  
Dbd Plasma ◽  
Nitrogen Fixing Bacteria ◽  
Free Living ◽  
Reduction Assay ◽  
Rrna Sequencing

Nitrogen-fixing bacteria were screened from the rhizosphere soil of plants in Shaanxi in China. 36 free-living nitrogen-fixing bacterial strains were isolated and their nitrogenase activity were determined by acetylene reduction assay (ARA), two strains named FLNB03 and FLNB09 with higher nitrogenase activity were isolated and identified by 16S rRNA sequencing. The datum showed that FLNB03 was similar to Acinetobacter and their similarity reached 99%, FLNB09 was similar to Agrobacterium sp. and their similarity reached 99%. Then both of them were treated using Dielectric Barrier Discharge (DBD) plasma for mutation and their mutants called FLNB03-2 and FLNB09-3 were obtained. The nitrogenase activity of FLNB03-2 was 0.61±0.10 nmol•107cfu-1•h-1, and that of FLNB09-3 was 0.40±0.05 nmol•107cfu-1•h-1, their nitrogenase activity increased by 22.00% and 14.29% than their original bacteria respectively. FLNB03-2 and FLNB09-3 might be used as microbial fertilizer.

Field measurements of nitrogenase activity in soils amended with wheat straw

1983 ◽  
Vol 34 (6) ◽  
pp. 725 ◽  
Author(s):  
MM Roper
Keyword(s):  
Nitrogenase Activity ◽  
New South ◽  
Field Measurements ◽  
Field Capacity ◽  
Nitrogen Fertilizers ◽  
Free Living ◽  
Straw Decomposition ◽  
Indirect Measure ◽  
South Wales

Nitrogenase activity and decomposition of straw were examined in situ in two areas (Gunnedah and Cowra) representative of large areas of the New South Wales wheat belt. Measurements of nitrogenase activity were made by adapting the acetylene reduction assay for use in the field. Evolution of CO2 was monitored as an indirect measure of decomposition of straw. The addition of straw to soil stimulated nitrogenase activity which was related to the amount of straw added and the rate of straw decomposition. There were significant levels of activity provided the soil was moist and warm. Nitrogenase activity increased with mean daily soil temperature (up to at least 30�C) and decreased as the soil dried from field capacity. It is concluded that nitrogen fixation by free-living nitrogen-fixing microorganisms in soils amended with straw may contribute to the nitrogen status of the soil and thus reduce the need for nitrogen fertilizers.

The acetylene reduction assay for measuring nitrogen fixation in waterlogged soil

1971 ◽  
Vol 17 (8) ◽  
pp. 1049-1056 ◽  
Author(s):  
W. A. Rice ◽  
E. A. Paul
Keyword(s):  
Nitrogen Fixation ◽  
Aqueous Phase ◽  
Nitrogenase Activity ◽  
Total Sample ◽  
Gas Diffusion ◽  
N Fixation ◽  
Waterlogged Soil ◽  
Sample Depth ◽  
Reduction Assay ◽  
Glucose System

Nitrogen fixation in waterlogged, soil–straw, and sand–clay–straw mixtures was measured with the C2H2 reduction assay, the 15N-tracer technique, and the Kjeldahl method. The reduction of 6 to 15 moles C2H2 corresponded to the fixation of 1 mole N2. The theoretical ratio is 3 moles C2H2 to 1 mole N2. A ratio of 3 moles C2H2 reduced for each mole of N2 fixed was obtained when samples of sand–clay–straw were incubated under conditions that minimized effects that were due to gas diffusion through the aqueous phase. Calculations indicated that N2 at a partial pressure of 0.2 atm above the samples was not sufficient to saturate the nitrogenase enzyme of the organisms in lower layers of soil–straw samples. Thus the concentration of N2 dissolved in the aqueous phase limited nitrogen fixation. C2H2 is more soluble in water than N2; the C2H2 reduction was not as limited by the C2H2 concentration in the aqueous phase.N2 was experimentally shown to be limited at depth in a sand–clay–glucose system in that fixation decreased from 128 to 36 μg N/g of sand–clay incubated so that the total sample depth ranged from 0.2 to 3 cm.The C2H2 reduction assay provides a method for measuring the potential nitrogenase activity in the waterlogged soil amended with straw; however, this assay must be calibrated for specific conditions. The data also indicate that where N2 diffusion rates may limit N fixation, a normal atmosphere (80%) of N2 should be used in the experiment.

Effects of the length of incubation period and herbicides on nitrogenase activity of pea (Pisum sativum L.)

2002 ◽  
Vol 50 (2) ◽  
pp. 135-143
Author(s):  
G. Singh ◽  
Keyword(s):  
Pisum Sativum ◽  
Incubation Period ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Pot Experiment ◽  
Flowering Stage ◽  
Seed Filling ◽  
Pisum Sativum L ◽  
Reduction Assay

In a pot experiment the effects of the length of incubation period and the pre-emergence application of terbutryn/terbuthylazine at 2.80 kg a.i. ha-1 or post-emergence application of bentazone at 2.88 kg a.i. ha-1 on the nitrogenase activity in intact pea plants were measured in situ by the acetylene reduction assay. An incubation period of 10 min resulted in the highest nitrogenase activity. As the length of the incubation period increased to 30 or 60 min the total as well as the specific nitrogenase activity decreased. Terbutryn/terbuthylazine decreased the total nitrogenase activity at all three (i.e. vegetative, flowering and seed-filling) stages, whereas bentazone resulted in a significant decrease at the flowering stage only. However, terbutryn/terbuthylazine-treated plants had the highest specific nitrogenase activity both at the flowering and seed-filling stages.

A new method for the in situ assay of α-glucosidase activity and inhibitor screening through an enzyme substrate-mediated DNA hybridization chain reaction

2019 ◽  
Vol 43 (24) ◽  
pp. 9458-9465
Author(s):  
Xiquan Yue ◽  
Lihong Su ◽  
Xu Chen ◽  
Junfeng Liu ◽  
Longpo Zheng ◽  
...  
Keyword(s):  
Small Molecule ◽  
Dna Hybridization ◽  
New Method ◽  
Hybridization Chain Reaction ◽  
Chain Reaction ◽  
Inhibitor Screening ◽  
Glucosidase Activity ◽  
Enzyme Substrate ◽  
In Situ Assay

The strategy is based on small molecule-mediated hybridization chain reaction.

scholarly journals Network analysis of the left anterior descending coronary arteries in swim-trained rats by an in situ video microscopic technique

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Marianna Török ◽  
Petra Merkely ◽  
Anna Monori-Kiss ◽  
Eszter Mária Horváth ◽  
Réka Eszter Sziva ◽  
...  
Keyword(s):  
Sex Differences ◽  
Left Ventricular ◽  
Resistance Artery ◽  
Frequency Spectra ◽  
Stress Markers ◽  
Lv Mass ◽  
Network Properties ◽  
Exercise Induced ◽  
And Function

Abstract Background We aimed to identify sex differences in the network properties and to recognize the geometric alteration effects of long-term swim training in a rat model of exercise-induced left ventricular (LV) hypertrophy. Methods Thirty-eight Wistar rats were divided into four groups: male sedentary, female sedentary, male exercised and female exercised. After training sessions, LV morphology and function were checked by echocardiography. The geometry of the left coronary artery system was analysed on pressure-perfused, microsurgically prepared resistance artery networks using in situ video microscopy. All segments over > 80 μm in diameter were studied using divided 50-μm-long cylindrical ring units of the networks. Oxidative-nitrative (O-N) stress markers, adenosine A2A and estrogen receptor (ER) were investigated by immunohistochemistry. Results The LV mass index, ejection fraction and fractional shortening significantly increased in exercised animals. We found substantial sex differences in the coronary network in the control groups and in the swim-trained animals. Ring frequency spectra were significantly different between male and female animals in both the sedentary and trained groups. The thickness of the wall was higher in males as a result of training. There were elevations in the populations of 200- and 400-μm vessel units in males; the thinner ones developed farther and the thicker ones closer to the orifice. In females, a new population of 200- to 250-μm vessels appeared unusually close to the orifice. Conclusions Physical activity and LV hypertrophy were accompanied by a remodelling of coronary resistance artery network geometry that was different in both sexes.

scholarly journals Ultrafine metal-polymer catalysts based on polyconjugated systems for Fisher–Tropsch synthesis

2020 ◽  
Vol 92 (6) ◽  
pp. 977-984
Author(s):  
Mayya V. Kulikova ◽  
Albert B. Kulikov ◽  
Alexey E. Kuz’min ◽  
Anton L. Maximov
Keyword(s):  
Tropsch Synthesis ◽  
X Ray Diffraction ◽  
Fischer Tropsch ◽  
Force Microscopy ◽  
Composite Catalysts ◽  
Fe Catalyst ◽  
Atomic Force ◽  
And Function ◽  
Metal Polymer

AbstractFor previously studied Fischer–Tropsch nanosized Fe catalyst slurries, polymer compounds with or without polyconjugating structures are used as precursors to form the catalyst nanomatrix in situ, and several catalytic experiments and X-ray diffraction and atomic force microscopy measurements are performed. The important and different roles of the paraffin molecules in the slurry medium in the formation and function of composite catalysts with the two types of aforementioned polymer matrices are revealed. In the case of the polyconjugated polymers, the alkanes in the medium are “weakly” coordinated with the metal-polymer composites, which does not affect the effectiveness of the polyconjugated polymers. Otherwise, alkane molecules form a “tight” surface layer around the composite particles, which create transport complications for the reagents and products of Fischer-Tropsch synthesis and, in some cases, can change the course of the in situ catalyst formation.

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