Asymbiotic N2-fixing bacteria associated with three boreal conifers

1984 ◽  
Vol 14 (4) ◽  
pp. 595-597 ◽  
Author(s):  
L. Z. Florence ◽  
F. D. Cook
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Seedling Root ◽  
Natural Stands

Azotobacter spp., Azospirillum spp., and Desulfovibrio spp., were identified as the predominant nitrogen-fixing bacteria associated with seedling root sections collected from natural stands of Pinusbanksiana Lamb., Piceamariana (Mill.) B.S.P., and Larixlaricina (Du Roi) K. Koch growing in Alberta. Samples from the sandy upland habitat of P. banksiana exhibited lower average rates of nitrogen fixation relative to the wet lowland occupied by P. mariana and L. laricina. Average nitrogen-fixing capacity (by acetylene reduction) was greater among bacteria isolates from L. laricina than those from P. mariana. Azospirillum spp. were strongly associated with P. mariana, while Azotobacter spp. were isolated more frequently from L. laricina.

scholarly journals Nitrogen Fixation in Pozol, a Traditional Fermented Beverage

2020 ◽  
Vol 86 (16) ◽  
Author(s):  
Jocelin Rizo ◽  
Marco A. Rogel ◽  
Daniel Guillén ◽  
Carmen Wacher ◽  
Esperanza Martinez-Romero ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Growth Promotion ◽  
Point Of View ◽  
Intestinal Microbiome ◽  
Acetylene Reduction Activity ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Free Living ◽  
Functional Perspective

ABSTRACT Traditional fermentations have been widely studied from the microbiological point of view, but little is known from the functional perspective. In this work, nitrogen fixation by free-living nitrogen-fixing bacteria was conclusively demonstrated in pozol, a traditional Mayan beverage prepared with nixtamalized and fermented maize dough. Three aspects of nitrogen fixation were investigated to ensure that fixation actually happens in the dough: (i) the detection of acetylene reduction activity directly in the substrate, (ii) the presence of potential diazotrophs, and (iii) an in situ increase in acetylene reduction by inoculation with one of the microorganisms isolated from the dough. Three genera were identified by sequencing the 16S rRNA and nifH genes as Kosakonia, Klebsiella, and Enterobacter, and their ability to fix nitrogen was confirmed. IMPORTANCE Nitrogen-fixing bacteria are found in different niches, as symbionts in plants, in the intestinal microbiome of several insects, and as free-living microorganisms. Their use in agriculture for plant growth promotion via biological nitrogen fixation has been extensively reported. This work demonstrates the ecological and functional importance that these bacteria can have in food fermentations, reevaluating the presence of these genera as an element that enriches the nutritional value of the dough.

A Survey of Asymbiotic Nitrogen Fixation in the Rhizosphere of Weeds

Weed Science ◽  
1978 ◽  
Vol 26 (2) ◽  
pp. 148-150 ◽  
Author(s):  
A. R. Conklin ◽  
P. K. Biswas
Keyword(s):  
Thin Film ◽  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Rhizosphere Soil ◽  
Soil Samples ◽  
Reduction Technique ◽  
Nitrogen Fixing ◽  
Weed Species ◽  
Nitrogen Fixing Bacteria ◽  
Asymbiotic Nitrogen Fixation

The occurrence of asymbiotic nitrogen fixing bacteria in the rhizosphere of twenty weed species has been investigated. Using the roll tube method root-rhizosphere soil samples were diluted and added to test tubes containing low N media. Tubes were flushed with nitrogen, stoppered, and rolled to form a thin film of media on the inner wall. After 7 days incubation the nitrogen fixation rates were estimated using the acetylene reduction technique. Rates ranged from 38 to 783 nmoles acetylene reduced per hour. Of twenty species tested, three showed high rhizosphere populations of asymbiotic nitrogen fixing bacteria.

Use of Pankhurst tubes to assay acetylene reduction by facultative and anaerobic nitrogen-fixing bacteria

1969 ◽  
Vol 15 (11) ◽  
pp. 1342-1343 ◽  
Author(s):  
N. E. R. Campbell ◽  
Harold J. Evans
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Most Probable Number ◽  
Bacterial Isolates ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Probable Number ◽  
Density Measurements ◽  
Large Numbers ◽  
Root Surfaces

Pankhurst tubes are simple and inexpensive vessels in which to screen large numbers of bacterial isolates by the acetylene reduction test for nitrogen fixation. A modification is described which allows, in addition, optical density measurements of growth. The method is well suited to most probable number estimations of facultative and anaerobic nitrogen-fixing bacteria in soils and on root surfaces.

scholarly journals Genomic characterization and computational phenotyping of nitrogen-fixing bacteria isolated from Colombian sugarcane fields

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luz K. Medina-Cordoba ◽  
Aroon T. Chande ◽  
Lavanya Rishishwar ◽  
Leonard W. Mayer ◽  
Lina C. Valderrama-Aguirre ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Nitrogen Fixation ◽  
Plant Growth ◽  
Phosphate Solubilization ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Promising Tool ◽  
A Genome ◽  
Plant Growth Promoting ◽  
Growth Promoting

AbstractPrevious studies have shown the sugarcane microbiome harbors diverse plant growth promoting microorganisms, including nitrogen-fixing bacteria (diazotrophs), which can serve as biofertilizers. The genomes of 22 diazotrophs from Colombian sugarcane fields were sequenced to investigate potential biofertilizers. A genome-enabled computational phenotyping approach was developed to prioritize sugarcane associated diazotrophs according to their potential as biofertilizers. This method selects isolates that have potential for nitrogen fixation and other plant growth promoting (PGP) phenotypes while showing low risk for virulence and antibiotic resistance. Intact nitrogenase (nif) genes and operons were found in 18 of the isolates. Isolates also encode phosphate solubilization and siderophore production operons, and other PGP genes. The majority of sugarcane isolates showed uniformly low predicted virulence and antibiotic resistance compared to clinical isolates. Six strains with the highest overall genotype scores were experimentally evaluated for nitrogen fixation, phosphate solubilization, and the production of siderophores, gibberellic acid, and indole acetic acid. Results from the biochemical assays were consistent and validated computational phenotype predictions. A genotypic and phenotypic threshold was observed that separated strains by their potential for PGP versus predicted pathogenicity. Our results indicate that computational phenotyping is a promising tool for the assessment of bacteria detected in agricultural ecosystems.

Endophytic nitrogen fixation – a possible ‘hidden’ source of nitrogen for lodgepole pine trees growing at unreclaimed gravel mining sites

2019 ◽  
Vol 95 (11) ◽  
Author(s):  
Kiran Preet Padda ◽  
Akshit Puri ◽  
Chris Chanway
Keyword(s):  
Nitrogen Fixation ◽  
Lodgepole Pine ◽  
Nifh Gene ◽  
Control Treatment ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Mining Sites ◽  
Greenhouse Study ◽  
Gravel Mining ◽  
Pine Trees

ABSTRACT Lodgepole pine (Pinus contorta var. latifolia) trees have been thriving on unreclaimed gravel mining sites in British Columbia, Canada, with tissue nitrogen-content and growth-rate unaffected by extremely low soil nitrogen-levels. This indicates that pine trees could be accessing a hidden nitrogen source to fulfill their nitrogen requirements – possibly via endophytic nitrogen-fixation. Endophytic bacteria originally isolated from native pine trees growing at gravel sites were selected (n = 14) for in vitro nitrogen-fixation assays and a year long greenhouse study to test the overall hypothesis that naturally occurring endophytic nitrogen-fixing bacteria sustain pine tree growth under nitrogen-limited conditions. Each of the 14 bacteria colonized the internal tissues of pine trees in the greenhouse study and fixed significant amounts of nitrogen from atmosphere (23%–53%) after one year as estimated through 15N isotope dilution assay. Bacterial inoculation also significantly enhanced the length (31%–64%) and biomass (100%–311%) of pine seedlings as compared to the non-inoculated control treatment. In addition, presence of the nifH gene was confirmed in all 14 bacteria. Our results support the possibility that pine trees associate with nitrogen-fixing bacteria, capable of endophytic colonization, to survive at unreclaimed gravel mining pits and this association could potentially be utilized for effective reclamation of highly disturbed sites in a sustainable manner.

Changes in acetylene reduction activities and effects of inoculated rhizosphere nitrogen-fixing bacteria on rice

2005 ◽  
Vol 41 (5) ◽  
pp. 371-378 ◽  
Author(s):  
Zhe Piao ◽  
Zongjun Cui ◽  
Bin Yin ◽  
Jian Hu ◽  
Chunhong Zhou ◽  
...  
Keyword(s):  
Acetylene Reduction ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria

Potential for nitrogen fixation in the rhizosphere and habitat of natural stands of the wild rice Zizania aquatica

1979 ◽  
Vol 57 (11) ◽  
pp. 1285-1291 ◽  
Author(s):  
M. T. Ogan
Keyword(s):  
Nitrogen Fixation ◽  
Water Column ◽  
Acetylene Reduction ◽  
Wild Rice ◽  
Heterotrophic Bacteria ◽  
Nitrogenase Activity ◽  
Early Summer ◽  
Zizania Aquatica ◽  
Natural Stands ◽  
Root Surfaces

The potential for nitrogen fixation in the rhizosphere and habitat of natural stands of Zizania aquatica (L) was studied by the acetylene reduction method. The data obtained suggested that this potential exists in the water column, the rhizosphere soil of the wild rice habitat, and on the root surfaces of the plants.In situ determination of rates of nitrogen fixation in the water column showed low but significant levels only in late spring – early summer and the rate was thought to be dependent on the presence of the blue-green algae Aphanizomenon. Laboratory experimental evidence showed that acetylene reduction by rhizosphere surface soil was attributable to Oscillatoria species while bacteria were more active in the subsurface soil and on the root surfaces. The bacteria-mediated nitrogenase activity was often preceded by a long lag period. The heterotrophic bacteria involved were enumerated, isolated, and characterised and they belong to the genera Azotobacter and Clostridium. Algal components of blooms occurring within the stands of Zizania at various times were identified.

scholarly journals Differing Courses of Genetic Evolution of Bradyrhizobium Inoculants as Revealed by Long-Term Molecular Tracing in Acacia mangium Plantations

2014 ◽  
Vol 80 (18) ◽  
pp. 5709-5716 ◽  
Author(s):  
M. M. Perrineau ◽  
C. Le Roux ◽  
A. Galiana ◽  
A. Faye ◽  
R. Duponnois ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Growth Promotion ◽  
Acacia Mangium ◽  
Housekeeping Genes ◽  
Nitrogen Fixing ◽  
Microbial Inoculants ◽  
Nitrogen Fixing Bacteria ◽  
Content Type ◽  
Significant Difference

ABSTRACTIntroducing nitrogen-fixing bacteria as an inoculum in association with legume crops is a common practice in agriculture. However, the question of the evolution of these introduced microorganisms remains crucial, both in terms of microbial ecology and agronomy. We explored this question by analyzing the genetic and symbiotic evolution of twoBradyrhizobiumstrains inoculated onAcacia mangiumin Malaysia and Senegal 15 and 5 years, respectively, after their introduction. Based on typing of several loci, we showed that these two strains, although closely related and originally sampled in Australia, evolved differently. One strain was recovered in soil with the same five loci as the original isolate, whereas the symbiotic cluster of the other strain was detected with no trace of the three housekeeping genes of the original inoculum. Moreover, the nitrogen fixation efficiency was variable among these isolates (either recombinant or not), with significantly high, low, or similar efficiencies compared to the two original strains and no significant difference between recombinant and nonrecombinant isolates. These data suggested that 15 years after their introduction, nitrogen-fixing bacteria remain in the soil but that closely related inoculant strains may not evolve in the same way, either genetically or symbiotically. In a context of increasing agronomical use of microbial inoculants (for biological control, nitrogen fixation, or plant growth promotion), this result feeds the debate on the consequences associated with such practices.

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