The Unusual Symbiosis Between the Nitrogen Fixing Bacterium ORS571 and Its Host Sesbania Rostrata: Regulation of Nitrogen Fixation and Assimilation Genes in the Free Living Versus Symbiotic State

1987 ◽  
pp. 266-271 ◽  
Author(s):  
F. de Bruijn ◽  
K. Pawlowski ◽  
P. Ratet ◽  
U. Hilgert ◽  
J. Schell
Keyword(s):  
Nitrogen Fixation ◽  
Sesbania Rostrata ◽  
Nitrogen Fixing ◽  
Free Living

NON-SYMBIOTIC NITROGEN FIXATION IN SOME QUEBEC SOILS

1965 ◽  
Vol 11 (1) ◽  
pp. 29-38 ◽  
Author(s):  
P-C. Chang ◽  
R. Knowles
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Soil Types ◽  
Anaerobic Incubation ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Aerobic Conditions ◽  
Bacterial Counts ◽  
Facultatively Anaerobic ◽  
Nitrogen Fixers

The occurrence of free-living nitrogen fixers, the potential for nitrogen fixation, and the correlation between the nitrogen-fixing capacities of the soils and bacterial counts were studied using representative Quebec soils.Clostridium occurred more frequently than did Azotobacter. Studies with N15showed that nitrogen fixation was more frequent under anaerobic than under aerobic conditions in all the soil types studied in their unamended state. The addition of glucose stimulated nitrogen fixation. During anaerobic incubation, nitrogen fixation was found to be correlated significantly with the increase in numbers of both total aerobes and Clostridia. The results suggested that facultatively anaerobic nitrogen fixers, and aerobic nitrogen fixers other than Azotobacter, were present.

Genetics of plant-microbe nitrogen-fixing symbiosis

1985 ◽  
Vol 85 (3-4) ◽  
pp. 239-252
Author(s):  
G. C. Machray ◽  
W. D. P. Stewart
Keyword(s):  
Nitrogen Fixation ◽  
Genetic Analysis ◽  
Symbiotic Nitrogen Fixation ◽  
Model System ◽  
Present Knowledge ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Genetic Level ◽  
And Control ◽  
Control Of Expression

SynopsisA wide variety of plant-microbe nitrogen-fixing symbioses which include cyanobacteria as the nitrogenfixing partner exist. While some information has been gathered on the biochemical changes in the cyanobacterium upon entering into symbiosis, very little is known about the accompanying changes at the genetic level. Much of our present knowledge of the organisation and control of expression of nitrogenfixation (nif) genes is derived from studies of the free-living diazotroph Klebsiella pneumoniae. This organism thus provides a model system and source of experimental material for the genetic analysis of symbiotic nitrogen fixation. We describe the use of cloned K. pneumoniae genes for nitrogen fixation and its regulation in the genetic analysis' of nitrogen fixation in cyanobacteria which can enter into symbiosis with plants. These studies reveal some dissimilarities in the organisation of nif genes and raise questions as to the genetic control of nitrogen fixation in symbiosis.

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.

scholarly journals DNA Methylation in Ensifer Species during Free-Living Growth and during Nitrogen-Fixing Symbiosis with Medicago spp.

mSystems ◽  
2022 ◽  
Author(s):  
George C. diCenzo ◽  
Lisa Cangioli ◽  
Quentin Nicoud ◽  
Janis H. T. Cheng ◽  
Matthew J. Blow ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Methylation ◽  
Nitrogen Fixation ◽  
Terminal Differentiation ◽  
Nitrogen Fixing ◽  
Bacterial Transformation ◽  
Free Living

Nitrogen fixation by rhizobia in symbiosis with legumes is economically and ecologically important. The symbiosis can involve a complex bacterial transformation—terminal differentiation—that includes major shifts in the transcriptome and cell cycle.

scholarly journals Identification by Suppression Subtractive Hybridization of Frankia Genes Induced under Nitrogen-Fixing Conditions

2010 ◽  
Vol 76 (5) ◽  
pp. 1692-1694 ◽  
Author(s):  
Masatoshi Yamaura ◽  
Toshiki Uchiumi ◽  
Shiro Higashi ◽  
Mikiko Abe ◽  
Ken-ichi Kucho
Keyword(s):  
Nitrogen Fixation ◽  
Suppression Subtractive Hybridization ◽  
Unknown Function ◽  
Subtractive Hybridization ◽  
Living Conditions ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Free Living Conditions

ABSTRACT Frankia is an actinobacterium that fixes nitrogen under both symbiotic and free-living conditions. We identified genes upregulated in free-living nitrogen-fixing cells by using suppression subtractive hybridization. They included genes with predicted functions related to nitrogen fixation, as well as with unknown function. Their upregulation was a novel finding in Frankia.

scholarly journals A Chemotaxis Receptor Modulates Nodulation during the Azorhizobium caulinodans-Sesbania rostrata Symbiosis

2016 ◽  
Vol 82 (11) ◽  
pp. 3174-3184 ◽  
Author(s):  
Nan Jiang ◽  
Wei Liu ◽  
Yan Li ◽  
Hailong Wu ◽  
Zhenhai Zhang ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Chemotaxis ◽  
Sesbania Rostrata ◽  
Nitrogen Fixing ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Free Living ◽  
Content Type

ABSTRACTAzorhizobium caulinodansORS571 is a free-living nitrogen-fixing bacterium which can induce nitrogen-fixing nodules both on the root and the stem of its legume hostSesbania rostrata. This bacterium, which is an obligate aerobe that moves by means of a polar flagellum, possesses a single chemotaxis signal transduction pathway. The objective of this work was to examine the role that chemotaxis and aerotaxis play in the lifestyle of the bacterium in free-living and symbiotic conditions. In bacterial chemotaxis, chemoreceptors sense environmental changes and transmit this information to the chemotactic machinery to guide motile bacteria to preferred niches. Here, we characterized a chemoreceptor ofA. caulinodanscontaining an N-terminal PAS domain, named IcpB. IcpB is a soluble heme-binding protein that localized at the cell poles. AnicpBmutant strain was impaired in sensing oxygen gradients and in chemotaxis response to organic acids. Compared to the wild-type strain, theicpBmutant strain was also affected in the production of extracellular polysaccharides and impaired in flocculation. When inoculated alone, theicpBmutant induced nodules onS. rostrata, but the nodules formed were smaller and had reduced N2-fixing activity. TheicpBmutant failed to nodulate its host when inoculated competitively with the wild-type strain. Together, the results identify chemotaxis and sensing of oxygen by IcpB as key regulators of theA. caulinodans-S. rostratasymbiosis.IMPORTANCEBacterial chemotaxis has been implicated in the establishment of various plant-microbe associations, including that of rhizobial symbionts with their legume host. The exact signal(s) detected by the motile bacteria that guide them to their plant hosts remain poorly characterized.Azorhizobium caulinodansORS571 is a diazotroph that is a motile and chemotactic rhizobial symbiont ofSesbania rostrata, where it forms nitrogen-fixing nodules on both the roots and the stems of the legume host. We identify here a chemotaxis receptor sensing oxygen inA. caulinodansthat is critical for nodulation and nitrogen fixation on the stems and roots ofS. rostrata. These results identify oxygen sensing and chemotaxis as key regulators of theA. caulinodans-S. rostratasymbiosis.

scholarly journals Artificial activation of nif gene expression in nodule bacteria Ex Planta

2019 ◽  
Vol 17 (2) ◽  
pp. 35-42
Author(s):  
Andrey K. Baymiev ◽  
Roman S. Gumenko ◽  
Anastasiya A. Vladimirova ◽  
Ekaterina S. Akimova ◽  
Zilya R. Vershinina ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Regulatory Protein ◽  
Inducible Promoter ◽  
Nitrogen Fixing ◽  
Nodule Bacteria ◽  
Free Living ◽  
Living State ◽  
Artificial Activation ◽  
Nifa Gene

Background. Rhizobia are the most effective nitrogen-fixing organisms that can fix nitrogen only in symbiosis with leguminous plants. The general transcriptional activator of nitrogen fixation genes in diazotrophic bacteria is NifA. In this work, the possibility of modifying the regulation of nitrogen fixation in the nodule bacteria Mesorhizobium, Ensifer and Rhizobium was studied by introducing an additional copy of the nifA gene into the bacterial genomes during the regulation of induced bacterial promoters. Materials and methods. A series of expression genetic constructs with NifA genes of nodule bacteria strains under the control of an inducible promoter Pm were created. The resulting constructs were transformed into strains of nodule bacteria. The obtained recombinant strains were investigated for the appearance of their nitrogen-fixing activity in the free-living state. Results. It was shown that the expression of nifA in recombinant cells of all three genera of bacteria leads to the appearance of insignificant nitrogenase activity. At the same time, the level of nitrogenase activity does not have a correlation with the level of expression of the introduced nifA gene, which, most likely, is a consequence of the multilevel regulation of nitrogen fixation. Conclusion. The possibility of artificial activation of nitrogenase activity in nodule bacteria in the free-living state by introducing the NifA regulatory protein gene into bacteria was shown.

Fifty years of sustainable no-tillage agriculture in the semi-arid Canadian Prairies

2020 ◽  
Author(s):  
Sina Adl ◽  
Manoj Kumar ◽  
Lucia Paupescu
Keyword(s):  
Nitrogen Fixation ◽  
Food Web ◽  
Size Distribution ◽  
Aggregate Size ◽  
No Tillage ◽  
Nitrogen Fixing ◽  
Free Living ◽  
Canadian Prairies ◽  
Aggregate Size Distribution ◽  
Semi Arid

<p>Fifty years of sustainable no-tillage agriculture in the semi-arid Canadian Prairies </p><p>Agriculture collapsed in the Canadian Prairies during the multi-year drought of 1926-1934. Two changes to local agriculture practice became critical in the recovery of top-soil and agricultural yield. One was abandonment of summer fallow, the other was adoption of no-tillage techniques pioneered in this region. We have obtained soil samples from commercial fields in cereal production (up to one century), from long-term experimental field-plots at research stations, from undisturbed prairies, and from secondary grasslands converted from agriculture. The data provides a chronosequence of fields about 40 years in continuous no-tillage, to contrast against fields in traditional tillage, against secondary grasslands, and undisturbed native prairie. For all samples, we measured free-living nitrogen fixation capacity (15N) in the laboratory, aggregate size distribution, microbial nitrogen fixing community (<em>nif</em> gene), and both bacteria (16S DNA) and eukaryote (18S DNA) diversity. We reconstructed eukaryote community structure and food web structure for the fields. Our results indicate that despite decades of continuous no-tillage, free-living nitrogen fixing capacity remains far below undisturbed prairies, but improved from ploughed fields. Soil aggregate size distribution remains lower in continuous no-tillage, but grasslands contain more larger-sized aggregates enabling more nitrogen fixation. Biodiversity indices follow a pattern of reduced diversity with increased disturbance from agriculture. Biodiversity improves with years into no-tillage or abandonment to secondary grasslands. Overall, we had anticipated a greater recovery of biodiversity, food web complexity, and of free-living nitrogen fixation in decades old continuous no-tillage fields, compared to continuous tillage. Nonetheless, the region of Canadian prairies in no-tillage has been resilient to cyclical droughts, and has accumulated soil organic carbon since adoption of no-tillage. The results are significant because about 95% of the area in cereal crops (~10 million Ha) is in no-tillage, and significant soil organic matter has accumulated in the agroecosystem to contribute to carbon storage to mitigate climate change. </p>

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