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Azospirillum brasilense

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Yaacov Okon – 1st expert on this subject based on the ideXlab platform

  • Characterization of Genes Involved in Poly-β- Hydroxybutyrate Metabolism in Azospirillum brasilense
    Symbiosis, 2020
    Co-Authors: Zohar Edelshtein, Jos Vanderleyden, Daniel Kadouri, Edouard Jurkevitch, Ann Vande Broek, Yaacov Okon

    Abstract:

    Under suboptimal growth conditions and like many other prokaryotes, rhizobacteria of the genus Azospirillum produce high levels of poly-βhydroxybutyrate (PHB). The two genes, bdhA (3-hydroxybutyrate dehydrogenase) and acsA2 (acetoacetyl-CoA synthetase), which are considered to be involved in the PHB degradation pathway in Azospirillum brasilense strain Sp7, were identified, cloned, and sequenced. Additionally, the expression of the bacterial genes phbA (βketothiolase) and phbC (PHB synthase), which are involved in PHB biosynthesis and the expression of the acsA2 gene, were studied using GUS fusions. Our results indicate that these genes are constitutively expressed in Azospirillum brasilense Sp7 and that the Ntr, PII and PZ nitrogen regulatory systems, which have been shown to be involved in the regulation of PHB synthesis, do not affect the expression of these genes. Expression of these genes is also shown to occur during association of A. brasilense with wheat roots.

  • key physiological properties contributing to rhizosphere adaptation and plant growth promotion abilities of Azospirillum brasilense
    Fems Microbiology Letters, 2012
    Co-Authors: Sharon Fibachpaldi, Saul Burdman, Yaacov Okon

    Abstract:

    Azospirillum brasilense is a plant growth promoting rhizobacterium (PGPR) that is being increasingly used in agriculture in a commercial scale. Recent research has elucidated key properties of A. brasilense that contribute to its ability to adapt to the rhizosphere habitat and to promote plant growth. They include synthesis of the auxin indole-3-acetic acid, nitric oxide, carotenoids, and a range of cell surface components as well as the ability to undergo phenotypic variation. Storage and utilization of polybetahydroxyalkanoate polymers are important for the shelf life of the bacteria in production of inoculants, products containing bacterial cells in a suitable carrier for agricultural use. Azospirillum brasilense is able to fix nitrogen, but despite some controversy, as judging from most systems evaluated so far, contribution of fixed nitrogen by this bacterium does not seem to play a major role in plant growth promotion. In this review, we focus on recent advances in the understanding of physiological properties of A . brasilense that are important for rhizosphere performance and successful interactions with plant roots.

  • effect of Azospirillum brasilense coinoculated with rhizobium on phaseolus vulgaris flavonoids and nod factor production under salt stress
    Soil Biology & Biochemistry, 2008
    Co-Authors: Marta S Dardanelli, Yaacov Okon, Francisco Fernandez J De Cordoba, Rosario M Espuny, Miguel Angel Rodriguez Carvajal, Maria Soria E Diaz, Antonio Miguel Gil Serrano, Manuel Megias

    Abstract:

    The effects of salt upon Azospirillum brasilense strain Cd on plant growth, nodulation, flavonoid and lipochitooligosaccharide (LCOs-Nod factor) production, were sequentially followed after 4, 7 and 14 days during a Rhizobium-Phaseolus vulgaris cv. Negro Jamapa interaction, in a hydroponics growth system. Azospirillum brasilense promoted root branching in bean seedling roots and increased secretion of nod-gene-inducing flavonoid species, as detected by high-performance liquid chromatography (HPLC). The results also support that A. brasilense allows a longer, more persistent exudation of flavonoids by bean roots. A general positive effect of Azospirillum-Rhizobium coinoculation on the expression of nod-genes by Rhizobium tropici CIAT899 and Rhizobium etli ISP42, and on nodulation factor patterns, was observed in the presence of root exudates. The negative effects obtained under salt stress on nod-gene expression and on Nod factors’ appearance were relieved in coinoculated plants.

Jos Vanderleyden – 2nd expert on this subject based on the ideXlab platform

  • Characterization of Genes Involved in Poly-β- Hydroxybutyrate Metabolism in Azospirillum brasilense
    Symbiosis, 2020
    Co-Authors: Zohar Edelshtein, Jos Vanderleyden, Daniel Kadouri, Edouard Jurkevitch, Ann Vande Broek, Yaacov Okon

    Abstract:

    Under suboptimal growth conditions and like many other prokaryotes, rhizobacteria of the genus Azospirillum produce high levels of poly-βhydroxybutyrate (PHB). The two genes, bdhA (3-hydroxybutyrate dehydrogenase) and acsA2 (acetoacetyl-CoA synthetase), which are considered to be involved in the PHB degradation pathway in Azospirillum brasilense strain Sp7, were identified, cloned, and sequenced. Additionally, the expression of the bacterial genes phbA (βketothiolase) and phbC (PHB synthase), which are involved in PHB biosynthesis and the expression of the acsA2 gene, were studied using GUS fusions. Our results indicate that these genes are constitutively expressed in Azospirillum brasilense Sp7 and that the Ntr, PII and PZ nitrogen regulatory systems, which have been shown to be involved in the regulation of PHB synthesis, do not affect the expression of these genes. Expression of these genes is also shown to occur during association of A. brasilense with wheat roots.

  • The nodPQ genes in Azospirillum brasilense Sp7 are involved in sulfation of lipopolysaccharides.
    Environmental Microbiology, 2005
    Co-Authors: Els Vanbleu, Biswa Choudhury, Russell W. Carlson, Jos Vanderleyden

    Abstract:

    Summary

    Here we report on the presence of sulfated lipopolysaccharide molecules in Azospirillum brasilense, a plant growth-promoting rhizosphere bacterium. Chemical analysis provided structural data on the O-antigen composition and demonstrated the possible involvement of the nodPQ genes in O-antigen sulfation.

  • Identification and characterization of a periplasmic nitrate reductase in Azospirillum brasilense Sp245.
    Archives of Microbiology, 2001
    Co-Authors: Oda Steenhoudt, Yaacov Okon, Veerle Keijers, Jos Vanderleyden

    Abstract:

    The Azospirillum brasilense Sp245 napABC genes, encoding nitrate reductase activity, were isolated and sequenced. The derived protein sequences are very similar throughout the whole Nap segment to the NapABC protein sequences of Escherichia coli, Pseudomonas sp. G-179, Ralstonia eutropha, Rhodobacter sphaeroides, and Paracoccus denitrificans. Based on whole-cell nitrate reductase assays with the artificial electron donors benzyl viologen and methyl viologen, and assays with periplasmic cell-free extracts, it was concluded that the napABC-encoded enzyme activity in Azospirillum brasilense Sp245 corresponds to a periplasmic dissimilatory nitrate reductase, which was expressed under anoxic conditions and oxic conditions. A kanamycin-resistant Azospirillum brasilense Sp245 napA insertion mutant was constructed. The mutant still expressed assimilatory nitrate reductase activity, but was devoid of its periplasmic dissimilatory nitrate reductase activity.

Marta S Dardanelli – 3rd expert on this subject based on the ideXlab platform

  • reorganization of Azospirillum brasilense cell membrane is mediated by lipid composition adjustment to maintain optimal fluidity during water deficit
    Journal of Applied Microbiology, 2016
    Co-Authors: A Cesari, Natalia Soledad Paulucci, Maria Alicia Biasutti, Yanina Belen Reguera, L A Gallarato, Christopher Kilmurray, Marta S Dardanelli

    Abstract:

    AIMS: We study the Azospirillum brasilense tolerance to water deficit and the dynamics of adaptive process at the level of the membrane. METHODS AND RESULTS: Azospirillum brasilense was exposed to polyethylene glycol (PEG) growth and PEG shock. Tolerance, phospholipids and fatty acid (FA) composition and membrane fluidity were determined. Azospirillum brasilense was able to grow in the presence of PEG; however, its viability was reduced. Cells grown with PEG showed membrane fluidity similar to those grown without, the lipid composition was modified, increasing phosphatidylcholine and decreasing phosphatidylethanolamine amounts. The unsaturation FAs degree was reduced. The dynamics of the adaptive response revealed a decrease in fluidity 20 min after the addition of PEG, indicating that the PEG has a fluidizing effect on the hydrophobic region of the cell membrane. Fluidity returned to initial values after 60 min of PEG exposure. CONCLUSION: Azospirillum brasilense is able to perceive osmotic changes by changing the membrane fluidity. This effect is offset by changes in the composition of membrane phospholipid and FA, contributing to the homeostasis of membrane fluidity under water deficit. SIGNIFICANCE AND IMPACT OF THE STUDY: This knowledge can be used to develop new Azospirillum brasilense formulations showing an adapted membrane to water deficit.

  • effect of Azospirillum brasilense coinoculated with rhizobium on phaseolus vulgaris flavonoids and nod factor production under salt stress
    Soil Biology & Biochemistry, 2008
    Co-Authors: Marta S Dardanelli, Yaacov Okon, Francisco Fernandez J De Cordoba, Rosario M Espuny, Miguel Angel Rodriguez Carvajal, Maria Soria E Diaz, Antonio Miguel Gil Serrano, Manuel Megias

    Abstract:

    The effects of salt upon Azospirillum brasilense strain Cd on plant growth, nodulation, flavonoid and lipochitooligosaccharide (LCOs-Nod factor) production, were sequentially followed after 4, 7 and 14 days during a Rhizobium-Phaseolus vulgaris cv. Negro Jamapa interaction, in a hydroponics growth system. Azospirillum brasilense promoted root branching in bean seedling roots and increased secretion of nod-gene-inducing flavonoid species, as detected by high-performance liquid chromatography (HPLC). The results also support that A. brasilense allows a longer, more persistent exudation of flavonoids by bean roots. A general positive effect of Azospirillum-Rhizobium coinoculation on the expression of nod-genes by Rhizobium tropici CIAT899 and Rhizobium etli ISP42, and on nodulation factor patterns, was observed in the presence of root exudates. The negative effects obtained under salt stress on nod-gene expression and on Nod factors’ appearance were relieved in coinoculated plants.