scholarly journals Unique genome evolution in an intracellular N2-fixing symbiont of a rhopalodiacean diatom

2014 ◽  
Vol 83 (4) ◽  
pp. 409-413 ◽  
Author(s):  
Takuro Nakayama ◽  
Yuji Inagaki
Keyword(s):  
Nitrogen Fixation ◽  
Genome Evolution ◽  
Nitrogen Compounds ◽  
Diatom Species ◽  
Comparative Genome Analysis ◽  
Fixed Nitrogen ◽  
Metabolic Capacity ◽  
Symbiotic Relationships ◽  
The Family ◽  
Spheroid Body

Cyanobacteria, the major photosynthetic prokaryotic lineage, are also known as a major nitrogen fixer in nature. N<sub>2</sub>-fixing cyanobacteria are frequently found in symbioses with various types of eukaryotes and supply fixed nitrogen compounds to their eukaryotic hosts, which congenitally lack N<sub>2</sub>-fixing abilities. Diatom species belonging to the family Rhopalodiaceae also possess cyanobacterial symbionts called spheroid bodies. Unlike other cyanobacterial N<sub>2</sub>-fixing symbionts, the spheroid bodies reside in the cytoplasm of the diatoms and are inseparable from their hosts. Recently, the first spheroid body genome from a rhopalodiacean diatom has been completely sequenced. Overall features of the genome sequence showed significant reductive genome evolution resulting in a diminution of metabolic capacity. Notably, despite its cyanobacterial origin, the spheroid body was shown to be truly incapable of photosynthesis implying that the symbiont energetically depends on the host diatom. The comparative genome analysis between the spheroid body and another N<sub>2</sub>-fixing symbiotic cyanobacterial group corresponding to the UCYN-A phylotypes – both were derived from cyanobacteria closely related to genus <em>Cyanothece</em> – revealed that the two symbionts are on similar, but explicitly distinct tracks of reductive evolution. Intimate symbiotic relationships linked by nitrogen fixation as seen in rhopalodiacean diatoms may help us better understand the evolution and mechanisms of bacterium-eukaryote endosymbioses.

Investigations on the root nodule bacteria of leguminous plants: XIX. Influence of various factors on the excretion of nitrogenous compounds from the nodules

1937 ◽  
Vol 27 (3) ◽  
pp. 332-348 ◽  
Author(s):  
Artturi Ilmari Virtanen ◽  
Synnöve von Hausen ◽  
Tauno Laine
Keyword(s):  
Amino Acids ◽  
Nitrogen Fixation ◽  
Root Nodule ◽  
Nitrogen Nutrition ◽  
Nitrogen Compounds ◽  
Nodule Bacteria ◽  
Fixed Nitrogen ◽  
Nitrogenous Compounds ◽  
Primary Products ◽  
Equal Effectiveness

1. It has been shown experimentally that the excretion of nitrogen noted by us in cultures of inoculated legumes takes place from the nodule bacteria, probably from the intranodular ones, and not from the roots. No excretion of amino acids occurs in cultures of uninoculated legumes growing on nitrate nitrogen.2. Our earlier hypothesis that the legumes receive their nitrogen nutrition from the nodules in the form of organic nitrogen compounds, particularly amino acids, is in perfect accord with our new observations concerning the process of excretion. All facts indicate that the amino acids concerned are primary products of the nitrogen fixation, and not breakdown products of proteins. Bond's valuable work along quite different lines produced results which support this conclusion. He, however, did not study the chemical nature of the nitrogen compounds in question.3. The excretion of nitrogen occurs in media capable of absorbing the excreted nitrogen compounds (cellulose, kaolin, sand, soil). The demonstration of the excretion is not possible in water cultures except when very large quantities of water are used. On the basis of these facts a hypothesis is advanced to explain the nature of the excretion.4. The term total fixed nitrogen has been used as an expression for the extent of nitrogen fixation, while the term extent of excretion is employed to indicate that percentage of the total fixed nitrogen which is excreted from the nodules.5. The extent of excretion depends largely on the strain used for inoculation. With strains of apparently equal effectiveness in nitrogen fixation, the extent of excretion may vary considerably, so that actually such strains differ in their effectiveness.

scholarly journals Symbiotic Nitrogen Fixation and the Challenges to Its Extension to Nonlegumes

2016 ◽  
Vol 82 (13) ◽  
pp. 3698-3710 ◽  
Author(s):  
Florence Mus ◽  
Matthew B. Crook ◽  
Kevin Garcia ◽  
Amaya Garcia Costas ◽  
Barney A. Geddes ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Synthetic Biology ◽  
Biological Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Crop Plants ◽  
Symbiotic Relationships ◽  
Mutualistic Relationship ◽  
Interest In Research ◽  
Biological Nitrogen ◽  
Developed World

ABSTRACTAccess to fixed or available forms of nitrogen limits the productivity of crop plants and thus food production. Nitrogenous fertilizer production currently represents a significant expense for the efficient growth of various crops in the developed world. There are significant potential gains to be had from reducing dependence on nitrogenous fertilizers in agriculture in the developed world and in developing countries, and there is significant interest in research on biological nitrogen fixation and prospects for increasing its importance in an agricultural setting. Biological nitrogen fixation is the conversion of atmospheric N2to NH3, a form that can be used by plants. However, the process is restricted to bacteria and archaea and does not occur in eukaryotes. Symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen. This process is restricted mainly to legumes in agricultural systems, and there is considerable interest in exploring whether similar symbioses can be developed in nonlegumes, which produce the bulk of human food. We are at a juncture at which the fundamental understanding of biological nitrogen fixation has matured to a level that we can think about engineering symbiotic relationships using synthetic biology approaches. This minireview highlights the fundamental advances in our understanding of biological nitrogen fixation in the context of a blueprint for expanding symbiotic nitrogen fixation to a greater diversity of crop plants through synthetic biology.

The flavin transferase ApbE flavinylates the ferredoxin:NAD+-oxidoreductase Rnf required for N2 fixation in Azotobacter vinelandii

2021 ◽  
Author(s):  
Yulia V Bertsova ◽  
Marina V Serebryakova ◽  
Alexander A Baykov ◽  
Alexander V Bogachev
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Growth Defect ◽  
Deficient Mutant ◽  
Fixed Nitrogen ◽  
Oxidoreductase Activity ◽  
Threonine Residue ◽  
Ferredoxin Reductase ◽  
Relative Contribution ◽  
Fixation System

Abstract Azotobacter vinelandii, the model microbe in nitrogen fixation studies, uses the ferredoxin:NAD+-oxidoreductase Rnf to regenerate ferredoxin (flavodoxin) acting as an electron donor for nitrogenase. However, the relative contribution of Rnf into nitrogenase functioning is unknown because this bacterium contains another ferredoxin reductase, FixABCX. Furthermore, Rnf is flavinylated in the cell, but the importance and pathway of this modification reaction also remain largely unknown. We have constructed A. vinelandii cells with impaired activities of FixABCX and/or putative flavin transferase ApbE. The ApbE-deficient mutant could not produce covalently flavinylated membrane proteins and demonstrated a markedly decreased flavodoxin:NAD+ oxidoreductase activity and significant growth defect under diazotrophic conditions. The double ΔFix/ΔApbE mutation abolished the flavodoxin:NAD+ oxidoreductase activity and the ability of A. vinelandii to grow in the absence of fixed nitrogen source. ApbE flavinylated a truncated RnfG subunit of Rnf1 by forming a phosphoester bond between FMN and a threonine residue. These findings indicate that Rnf (presumably its Rnf1 form) is the major ferredoxin-reducing enzyme in the nitrogen fixation system and that the activity of Rnf depends on its covalent flavinylation by the flavin transferase ApbE.

scholarly journals Studies on Nitrogen Fixation by Blue-Green Algae

1942 ◽  
Vol 19 (1) ◽  
pp. 78-87
Author(s):  
G. E. FOGG
Keyword(s):  
Nitrogen Fixation ◽  
Green Algae ◽  
Anabaena Cylindrica ◽  
Fixed Nitrogen ◽  
Blue Green Algae ◽  
Combined Nitrogen

1. Anabaena cylindrica Lemin. has been obtained in pure unialgal bacteria-free culture. 2. Due precautions having been taken against contamination by other organisms and error due to absorption of fixed nitrogen from the atmosphere, this alga has been shown to possess the capacity of fixing nitrogen. 3. Nitrogen fixation does not take place in the presence of a sufficient quantity of readily available combined nitrogen.

Adaptive convergent evolution of genome proofreading in SARS-CoV2: insights into the Eigen’s paradox

2021 ◽  
Author(s):  
Keerthic Aswin ◽  
Srinivasan Ramachandran ◽  
Vivek T Natarajan
Keyword(s):  
Convergent Evolution ◽  
Genome Stability ◽  
Evolutionary History ◽  
Rna Binding ◽  
Phylogenetic Analyses ◽  
Comparative Genome Analysis ◽  
The Family ◽  
History Of ◽  
Key Residues

AbstractEvolutionary history of coronaviruses holds the key to understand mutational behavior and prepare for possible future outbreaks. By performing comparative genome analysis of nidovirales that contain the family of coronaviruses, we traced the origin of proofreading, surprisingly to the eukaryotic antiviral component ZNFX1. This common recent ancestor contributes two zinc finger (ZnF) motifs that are unique to viral exonuclease, segregating them from DNA proof-readers. Phylogenetic analyses indicate that following acquisition, genomes of coronaviruses retained and further fine-tuned proofreading exonuclease, whereas related families harbor substitution of key residues in ZnF1 motif concomitant to a reduction in their genome sizes. Structural modelling followed by simulation suggests the role of ZnF in RNA binding. Key ZnF residues strongly coevolve with replicase, and the helicase involved in duplex RNA unwinding. Hence, fidelity of replication in coronaviruses is a result of convergent evolution, that enables maintenance of genome stability akin to cellular proofreading systems.

The effect of Inoculation and cobalt application on the growth of and nitrogen fixation by sweet lupins

1978 ◽  
Vol 29 (6) ◽  
pp. 1191 ◽  
Author(s):  
DL Chatel ◽  
AD Robson ◽  
JW Gartrell ◽  
MJ Dilworth
Keyword(s):  
Nitrogen Fixation ◽  
Cell Division ◽  
Plant Growth ◽  
Nitrogen Content ◽  
Lupinus Angustifolius ◽  
Fixed Nitrogen ◽  
Soil Application ◽  
Seed Inoculation

The response of sweet lupins, Lupinus angustifolius L., to a soil application of cobalt and to seed inoculation was examined in both field and glasshouse experiments. Plant growth was dependent on nodule-fixed nitrogen, and the addition of cobalt increased the nitrogen content and the growth of the lupins in the absence of inoculation. Bacteroids in the nodules of inoculated plants without cobalt were found to be fewer and longer than those with cobalt, which suggests that cobalt is involved in the mechanism of rhizobial cell division.

Rhizobium as a factor in the re-establishment of legume-based pastures on clay soils of the wheat belt of north-western New South Wales

1998 ◽  
Vol 38 (6) ◽  
pp. 555 ◽  
Author(s):  
A. M. Bowman ◽  
D. M. Hebb ◽  
D. J. Munnich ◽  
J. Brockwell
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
New South ◽  
New South Wales ◽  
Clay Soils ◽  
Natural Fertility ◽  
Fixed Nitrogen ◽  
South Wales ◽  
Annual Medics ◽  
North Western

Summary. Populations of Rhizobium meliloti in self-mulching clay soils (Vertisols) at 48 sites on 27 properties in north-western New South Wales were classified according to number and ability to fix nitrogen with several species of Medicago. Rhizobia were counted using serial dilution, nodulation frequency, plant infection tests. Abilities of the soil populations to fix nitrogen were determined in the laboratory with whole-soil inoculation of Medicago seedlings in test tubes with shoots exposed to the atmosphere and roots within the tubes under bacteriological control, and in the field using a technique based on the natural abundance of 15N in the soil. The majority of soils contained >1000 cells of R. meliloti per gram. The major component of those populations fixed nitrogen with lucerne (Medicago sativa) and some components of some soils also fixed nitrogen with M. polymorpha, M. scutellata, M. littoralis, M. tornata, M. laciniata and Trigonella suavissima. However, a number of soils were located which contained few if any rhizobia effective in nitrogen fixation with M. polymorpha. Overall, the effectiveness of nitrogen fixation of the naturally occurring populations of R. meliloti in association with M. polymorpha, M. scutellata, M. littoralis and M. tornata was only 46% of the effectiveness of standard strains. At one particular site, where 10 lines of annual Medicago spp. were growing experimentally, fixed nitrogen as a proportion of shoot nitrogen averaged only 28%. At that site, there were no effective rhizobia for M. scutellata and it was wholly dependent on the soil as the source of its nitrogen. The results are discussed in relation to the need for a substantial input of legume nitrogen for restoring the natural fertility of self-mulching clay soils in degraded wheat lands of north-western New South Wales. It is suggested that lucerne, or perhaps other perennial Medicago spp., might fill this role better than annual medics such as M. polymorpha and M. scutellata that are more dependent than lucerne on specific strains of R. meliloti to meet their requirements for symbiotic nitrogen fixation.

Détermination de l'identité isotopique de l'azote fixé par le Frankia associé au genre Alnus

1988 ◽  
Vol 66 (7) ◽  
pp. 1241-1247 ◽  
Author(s):  
A. M. Domenach ◽  
F. Kurdali ◽  
C. Danière ◽  
R. Bardin
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Alnus Glutinosa ◽  
Natural Ecosystem ◽  
Free Medium ◽  
Fixed Nitrogen ◽  
Aerial Parts ◽  
Reference Plant ◽  
N Enrichment ◽  
N Natural Abundance

To use the 15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on the Frankia strains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in 15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness of Frankia strains and 15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in 15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.

scholarly journals Nitrogen Fixation in the Coralloid Roots of Macrozamia Communis L. Johnson

1965 ◽  
Vol 18 (6) ◽  
pp. 1135 ◽  
Author(s):  
FJ Bergersen ◽  
GS Kennedy ◽  
W Wittmann
Keyword(s):  
Nitrogen Fixation ◽  
Green Algae ◽  
Intact Plant ◽  
Large Excess ◽  
Fixed Nitrogen ◽  
Blue Green Algae ◽  
Plant Parts ◽  
Isotopic Method ◽  
Coralloid Roots

Coralloid roots of Macrozamia communis have been shown by the isotopic method to fix nitrogen when they contain the endophytic blue�green algae. Immature coralloid roots devoid of the endophyte did not fix nitrogen. Coralloid roots from glasshouse-grown plants fixed 2� 7 times as much nitrogen when illuminated than they did in the dark and the IfiN excess was about equally divided between fractions soluble or insoluble in 3N HCI. Coralloid roots excavated from beneath large fieldgrown plants were opaque and did not fix more nitrogen when illuminated than they did in the dark. Most of the newly fixed nitrogen was found in the buffered sucrose extract of crushed tissue. When an intact plant bearing coralloid roots was exposed to an atmosphere containing a large excess of IfiN. for 48 hr the IfiN was found to be distributed through the plant parts. Nitrogen fixed in the coralloid roots is thus available for the growth of the plant. The coralloid roots evolved small amounts of hydrogen.

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