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 DNA methylation patterns in bacteria of the genus Ensifer during free-living growth and during nitrogen-fixing symbiosis with Medicago spp

2021 ◽  
Author(s):  
George C. diCenzo ◽  
Lisa Cangioli ◽  
Quentin Nicoud ◽  
Janis H.T. Cheng ◽  
Matthew J. Blow ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Methylation ◽  
Nitrogen Fixation ◽  
Single Molecule ◽  
Dna Sequences ◽  
Regulatory Mechanism ◽  
Terminal Differentiation ◽  
Nitrogen Fixing ◽  
Genome Wide ◽  
A Genome

ABSTRACTMethylation of specific genomic DNA sequences is ubiquitous in bacteria and has known roles in immunity and regulation of cellular processes, such as the cell cycle. Here, we explored DNA methylation in bacteria of the genus Ensifer, including its potential role in regulating the process of terminal differentiation occurring during nitrogen-fixing symbiosis with legumes. Using single-molecule real-time sequencing, six unique genome-wide methylated motifs were identified across four Ensifer strains, five of which were strain-specific. These five motifs were nearly fully methylated across the genomes in all tested conditions, and they were not enriched in the promoter regions of symbiosis, carbon source, or cell cycle-regulated genes, suggesting that most DNA methylation is not a major regulatory mechanism in the genus Ensifer. Only the GANTC motif, recognized by the cell cycle-regulated CcrM methyltransferase, was methylated in all strains. In actively dividing cells, methylation of GANTC motifs increased progressively from the ori to ter region in each replicon, in agreement with a cell cycle-dependent regulation of CcrM. The GANTC methylation profile transited into a genome-wide pattern of near full methylation in the early stage of symbiotic differentiation, followed by a progressive decrease in methylation from the ori to ter regions of fully differentiated symbiotic bacteria. This is evidence of a dysregulated and constitutive CcrM activity during terminal differentiation, which we suggest is a driving factor for endoreduplication of terminally differentiated bacteroids.IMPORTANCENitrogen fixation by bacteria (rhizobia) in symbiosis with legumes is economically and ecologically important. In some cases, the symbiosis involves a complex bacterial transformation, known as terminal differentiation, that includes major shifts in the transcriptome and cell cycle. Epigenetic regulation via DNA methylation is an important regulatory mechanism contributing to the biology of diverse bacteria; however, the roles of DNA methylation in rhizobia and symbiotic nitrogen fixation have been poorly investigated. We show that aside from cell cycle regulation, DNA methylation is unlikely to be a major mechanism of transcriptional regulation in rhizobia and non-rhizobia of the genus Ensifer. However, we found strong evidence that the cell cycle methyltransferase CcrM is dysregulated during symbiosis, which may be a key factor driving the cell cycle switch in terminal differentiation and the establishment of effective rhizobium – legume symbioses. These novel results advance our understanding of this highly important, yet incompletely understood process.

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 Why Should Nodule Cysteine-Rich (NCR) Peptides Be Absent From Nodules of Some Groups of Legumes but Essential for Symbiotic N-Fixation in Others?

2021 ◽  
Vol 3 ◽  
Author(s):  
J. Allan Downie ◽  
Eva Kondorosi
Keyword(s):  
Nitrogen Fixation ◽  
Terminal Differentiation ◽  
N Fixation ◽  
Nitrogen Fixing ◽  
Bacterial Differentiation ◽  
Genes Encoding

In nitrogen-fixing nodules of legumes such as pea (Pisum) and Medicago spp. the plant induces terminal differentiation in the rhizobial endosymbionts by targeting nodule-specific cysteine-rich defensin-like peptides into the bacteria. However, in nodules of other legumes such as soybean and Lotus spp. terminal bacterial differentiation does not occur; these legumes lack genes encoding equivalent peptides controlling rhizobial development. Here, we review the effects of some of these peptides on rhizobia and address the question as to how and why such peptides may have evolved to enslave rhizobia and become essential for nitrogen fixation in some clades of legumes but not in others.

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 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.

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