scholarly journals Role and Regulation of Poly-3-Hydroxybutyrate in Nitrogen Fixation in Azorhizobium caulinodans

2021 ◽  
Author(s):  
Nick Crang ◽  
Khushboo Borah ◽  
Euan K. James ◽  
Beatriz Jorrín ◽  
Patrick Green ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodules ◽  
Carbon Sources ◽  
Laboratory Culture ◽  
Start Codon ◽  
Azorhizobium Caulinodans ◽  
Poor Growth ◽  
Putative Ribosome Binding Site ◽  
Transition Mutation ◽  
Open Access Article

An Azorhizobium caulinodans phaC mutant (OPS0865) unable to make poly-3-hydroxybutyrate (PHB), grows poorly on many carbon sources and cannot fix nitrogen in laboratory culture. However, when inoculated onto its host plant, Sesbania rostrata, the phaC mutant consistently fixed nitrogen. Upon reisolation from S. rostrata root nodules, a suppressor strain (OPS0921) was isolated that has significantly improved growth on a variety of carbon sources and also fixes nitrogen in laboratory culture. The suppressor retains the original mutation and is unable to synthesize PHB. Genome sequencing revealed a suppressor transition mutation, G to A (position 357,354), 13 bases upstream of the ATG start codon of phaR in its putative ribosome binding site (RBS). PhaR is the global regulator of PHB synthesis but also has other roles in regulation within the cell. In comparison with the wild type, translation from the phaR native RBS is increased approximately sixfold in the phaC mutant background, suggesting that the level of PhaR is controlled by PHB. Translation from the phaR mutated RBS (RBS*) of the suppressor mutant strain (OPS0921) is locked at a low basal rate and unaffected by the phaC mutation, suggesting that RBS* renders the level of PhaR insensitive to regulation by PHB. In the original phaC mutant (OPS0865), the lack of nitrogen fixation and poor growth on many carbon sources is likely to be due to increased levels of PhaR causing dysregulation of its complex regulon, because PHB formation, per se, is not required for effective nitrogen fixation in A. caulinodans. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

scholarly journals Characterization of Rhizobia from Root Nodule and Rhizosphere of Lablab purpureus and Vigna sinensis in Bangladesh

2017 ◽  
Vol 5 (1) ◽  
pp. 14 ◽  
Author(s):  
Safirun Pervin ◽  
Bushra Jannat ◽  
Sohana Al Sanjee
Keyword(s):  
Nitrogen Fixation ◽  
Congo Red ◽  
Root Nodules ◽  
Leguminous Plant ◽  
Lablab Purpureus ◽  
Bacterial Strains ◽  
Vigna Sinensis ◽  
Biochemical Tests ◽  
Isolation And Identification ◽  
Poor Growth

Nitrogen fixation resulting from mutual symbiosis of rhizobia and cultivated legume plants is therefore critical to food security as it directly affects agricultural production. Biological Nitrogen Fixation (BNF) can be an important factor in sustainable agriculture.The isolation and identification of different slow growing and fast growing rhizobial strains from the nodules of two leguminous plant species. Symbiotic nitrogen fixing Rhizobium spp. was isolated from (Lablab purpureus and Vigna sinensis). Nodules samples were collected from plants growing in different Districts of Bangladesh and the Glucose-Peptone Agar (GPA), Congo red, Yeast Mannitol Agar (YMA) containing 2% NaCl were employed to make presumptive decisions on the recognition and classification of the isolated bacterial strains. All the isolates were found with poor absorption of dye Congo red and little or no growth on the media of GPA and without altering the pH. Almost all of the isolates exhibit growth on 2% NaCl, poor growth on GPA, thus confirming the rhizobia. After biochemical tests like catalase test and citrate utilization test isolates were confirmed as Rhizobia. The presence of rhizobia on root nodules of leguminous Plant. Not only the leguminous Plant but also the rhizosphere contains rhizobia which help in soil fertilization.

scholarly journals Genetic Analysis of Mutations Affecting pckA Regulation in Rhizobium (Sinorhizobium) meliloti

Genetics ◽  
1997 ◽  
Vol 147 (4) ◽  
pp. 1521-1531 ◽  
Author(s):  
Magne Østerås ◽  
Shelley A P O'Brien ◽  
Turlough M Finan
Keyword(s):  
Sinorhizobium Meliloti ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Root Nodules ◽  
Genetic Regulation ◽  
Carbon Sources ◽  
Dicarboxylic Acids ◽  
Phenotypic Analysis ◽  
Gene Encoding ◽  
Type Locus ◽  
Rapid Induction

Abstract The enzyme phosphoenolpyruvate carboxykinase (Pck) catalyzes the first step in the gluconeogenic pathway in most organisms. We are examining the genetic regulation of the gene encoding Pck, pckA, in Rhizobium (now Sinorhizobium) meliloti. This bacterium forms N2-fixing root nodules on alfalfa, and the major energy sources supplied to the bacteria within these nodules are C4-dicarboxylic acids such as malate and succinate. R. meliloti cells growing in glucose minimal medium show very low pckA expression whereas addition of succinate to this medium results in a rapid induction of pckA transcription. We identified spontaneous mutations (rpk) that alter the regulation of pckA expression such that pckA is expressed in media containing the non-inducing carbon sources lactose and glucose. Genetic and phenotypic analysis allowed us to differentiate at least four rpk mutant classes that map to different locations on the R. meliloti chromosome. The wild-type locus corresponding to one of these rpk loci was cloned by complementation, and two Tn5 insertions within the insert DNA that no longer complemented the rpk mutation were identified. The nucleotide sequence of this region revealed that both Tn5 insertions lay within a gene encoding a protein homologous to the Ga1R/LacI family of transcriptional regulators that are involved in metabolism.

scholarly journals Mutation in the ntrR Gene, a Member of the vap Gene Family, Increases the Symbiotic Efficiency of Sinorhizobium meliloti

2001 ◽  
Vol 14 (7) ◽  
pp. 887-894 ◽  
Author(s):  
Boglárka Oláh ◽  
Erno Kiss ◽  
Zoltán Györgypál ◽  
Judit Borzi ◽  
Gyöngyi Cinege ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pathogenic Bacteria ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Nifh Gene ◽  
Dry Weight ◽  
Nodule Occupancy ◽  
Gene Encoding ◽  
Symbiotic Efficiency ◽  
Host Interactions

In specific plant organs, namely the root nodules of alfalfa, fixed nitrogen (ammonia) produced by the symbiotic partner Sinorhizobium meliloti supports the growth of the host plant in nitrogen-depleted environment. Here, we report that a derivative of S. meliloti carrying a mutation in the chromosomal ntrR gene induced nodules with enhanced nitrogen fixation capacity, resulting in an increased dry weight and nitrogen content of alfalfa. The efficient nitrogen fixation is a result of the higher expression level of the nifH gene, encoding one of the subunits of the nitrogenase enzyme, and nifA, the transcriptional regulator of the nif operon. The ntrR gene, controlled negatively by its own product and positively by the symbiotic regulator syrM, is expressed in the same zone of nodules as the nif genes. As a result of the nitrogen-tolerant phenotype of the strain, the beneficial effect of the mutation on efficiency is not abolished in the presence of the exogenous nitrogen source. The ntrR mutant is highly competitive in nodule occupancy compared with the wild-type strain. Sequence analysis of the mutant region revealed a new cluster of genes, termed the “ntrPR operon,” which is highly homologous to a group of vap-related genes of various pathogenic bacteria that are presumably implicated in bacterium-host interactions. On the basis of its favorable properties, the strain is a good candidate for future agricultural utilization.

scholarly journals NITROGEN FIXATION BY EXCISED SOY BEAN ROOT NODULES

1954 ◽  
Vol 208 (1) ◽  
pp. 29-39
Author(s):  
M.H. Aprison ◽  
Wayne E. Magee ◽  
R.H. Burris
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodules ◽  
Bean Root

scholarly journals Multimodal Spectroscopic Imaging of Pea Root Nodules to Assess the Nitrogen Fixation in the Presence of Biofertilizer Based on Nod-Factors

2021 ◽  
Vol 22 (23) ◽  
pp. 12991
Author(s):  
Katarzyna Susniak ◽  
Mikolaj Krysa ◽  
Dominika Kidaj ◽  
Monika Szymanska-Chargot ◽  
Iwona Komaniecka ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Mass Spectrometry Imaging ◽  
Root Nodules ◽  
Spectroscopic Imaging ◽  
Ionization Mass ◽  
Nod Factors ◽  
Pea Root ◽  
Ft Ir ◽  
Ir And Raman ◽  
Apparent Distribution

Multimodal spectroscopic imaging methods such as Matrix Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI MSI), Fourier Transform Infrared spectroscopy (FT-IR) and Raman spectroscopy were used to monitor the changes in distribution and to determine semi quantitatively selected metabolites involved in nitrogen fixation in pea root nodules. These approaches were used to evaluate the effectiveness of nitrogen fixation by pea plants treated with biofertilizer preparations containing Nod factors. To assess the effectiveness of biofertilizer, the fresh and dry masses of plants were determined. The biofertilizer was shown to be effective in enhancing the growth of the pea plants. In case of metabolic changes, the biofertilizer caused a change in the apparent distribution of the leghaemoglobin from the edges of the nodule to its centre (the active zone of nodule). Moreover, the enhanced nitrogen fixation and presumably the accelerated maturation form of the nodules were observed with the use of a biofertilizer.

Morphological and biochemical changes in peanut nodules during photosynthate stress

1992 ◽  
Vol 38 (6) ◽  
pp. 526-533 ◽  
Author(s):  
A. B. M. Siddique ◽  
A. K. Bal
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodules ◽  
Ultrastructural Level ◽  
Malate Synthase ◽  
Morphological Evidence ◽  
Lipid Bodies ◽  
Biochemical Status ◽  
Short Period ◽  
Infected Cells ◽  
Ultrastructural Damage

Nitrogen fixation in legume root nodules is believed to be supported by the supply of photosynthate of the current photoperiod. However, in peanut nodules, prolonged periods of darkness or detopping do not disrupt nitrogen fixation for at least 48 h. During this period, nodule oleosomes (lipid bodies) have been shown to decrease in number within the infected cells, and it has been suggested that lipids from oleosomes are mobilized to maintain the energy and carbon requirements of the nitrogen-fixing nodules. We present morphological evidence, at the ultrastructural level, for the utilization of oleosomes during photosynthate stress. The biochemical status of the nodule has also been assessed and correlated with ultrastructure. For comparison cowpea nodules were used that totally lacked oleosomes. In peanut nodules leghemoglobin and total protein remained unchanged along with integrated ultrastructure on nodule cells for 48 h, whereas in cowpea a decline in proteins with ultrastructural damage became apparent within a very short period of photosynthate stress. In peanut nodules empty or partially empty oleosomes were taken as evidence for their utilization during the stress period. Key words: N2 fixation, photosynthate stress, lipid bodies, catalase, malate synthase, peanut nodule, β-oxidation.

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