Book ChapterDOI
Ecophysiological aspects of growth and nitrogen fixation in Azospirillum spp.
TLDR
The nitrogenase activity of Azospirillum spp.Abstract:
The nitrogenase activity ofAzospirillum spp. is efficiently regulated by environmental factors. InA. brasilense andA. lipoferum a rapid ‘switch off’ of nitrogenase activity occurs after the addition of ammonium chloride. As in photosynthetic bacteria, a covalent modification of nitrogenase reductase (Fe-protein) is involved. InA. amazonense, a non-covalent mechanism causes only a partial inhibition of nitrogenase activity after ammonium chloride is added. In anaerobic conditions, nitrogenase reductase is also ‘switched off’ by a covalent modification inA. brasilense andA. lipoferum. Short-time exposure ofAzospirillum to increased oxygen levels causes a partially reversible inhibition of nitrogenase activity, but no covalent modification is involved.Azospirillum spp. show variations in their oxygen tolerance. High levels of carotenoids confer a slightly improved oxygen tolerance. Certain amino acids (e. g. glutamate, aspartate, histidine and serine) affect growth and nitrogen fixation differently inAzospirillum spp. Amino acids may influence growth and nitrogen fixation ofAzospirillum in the association with plants.Azospirillum brasilense andA. halopraeferens are the more osmotolerant species. They utilize most amino acids poorly and accumulate glycine betaine, which also occurs in osmotically stressed grasses as a compatible solute to counteract osmotic stress. Nitrogen fixation is stimulated by glycine betaine and choline. Efficient iron acquisition is a prerequisite for competitive and aerotoleran growth and for high nitrogenase activity.Azospirillum halopraeferens andA. amazonense assimilate iron reasonably well, whereas growth of someA. brasilense andA. lipoferum strains is severely inhibited by iron limitation and by competition with foreign microbial iron chelators. However, growth of certain iron-limitedA. brasilense strains is stimulated by the phytosiderophore mugineic acid. Thus, various plant-derived substances may stimulate growth and nitrogen fixation ofAzospirillum.read more
Citations
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Journal ArticleDOI
Plant-driven selection of microbes
TL;DR: The general part of the manuscript is followed by the more detailed presentation of specific examples for the selection and interaction of roots and microbes, such as in the rhizosphere of strawberry, potato and oilseed rape, where the soil-borne plant pathogen Verticillium dahliae can cause high yield losses; the potential of biocontrol by specific constituents of the Rhizosphere microbial community is demonstrated.
Book ChapterDOI
Strategies of plants for acquisition of iron
Horst Marschner,Volker Römheld +1 more
TL;DR: Understanding is poor concerning the processes taking place in the apoplasm of root rhizodermal cells and of the role of low-molecular-weight root exudates and siderophores in Fe acquisition of plants growing in soils of differing Fe availability.
Journal ArticleDOI
Osmoadaptation by rhizosphere bacteria.
Karen J. Miller,Janet M. Wood +1 more
TL;DR: The present review focuses on the osmoadaptive responses of three gram-negative rhizobacterial genera: Rhizobium, Azospirillum, and Pseudomonas and examines the compatible solutes and osmoprotectants utilized by various species within these genera.
Journal ArticleDOI
Deleterious rhizosphere bacteria: an integrating perspective
TL;DR: The capacity for fluctuation in the phytogenic function of rhizobacteria presents a challenge for management of DRB and manipulation of the rhizosphere to improve the sustainability of agriculture.
Journal ArticleDOI
The roots of the halophyte Salicornia brachiata are a source of new halotolerant diazotrophic bacteria with plant growth-promoting potential
TL;DR: Nitrogen fixation as well as plant growth-promoting traits such as indole acetic acid (IAA) production, phosphate solubilisation, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity were demonstrated.
References
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Book
Bergey's Manual of Systematic Bacteriology
TL;DR: BCL3 and Sheehy cite Bergey's manual of determinative bacteriology of which systematic bacteriology, first edition, is an expansion.
Journal ArticleDOI
Living with water stress: evolution of osmolyte systems
TL;DR: Osmolyte compatibility is proposed to result from the absence of osmolytes interactions with substrates and cofactors, and the nonperturbing or favorable effects of oSMolytes on macromolecular-solvent interactions.
Journal ArticleDOI
Beta-carotene: an unusual type of lipid antioxidant
G. W. Burton,Keith U. Ingold +1 more
TL;DR: New experiments in vitro show that beta-carotene belongs to a previously unknown class of biological antioxidants, and exhibits good radical-trapping antioxidant behavior only at partial pressures of oxygen significantly less than 150 torr, the pressure of oxygen in normal air.
Journal ArticleDOI
Enhanced plant growth by siderophores produced by plant growth-promoting rhizobacteria
TL;DR: Evidence is presented that PGPR exert their plant growth-promoting activity by depriving native microflora of iron by producing extracellular siderophores (microbial iron transport agents) which efficiently complex environmental iron, making it less available to certain nativemicroflora.
Journal ArticleDOI
Evidence for a specific uptake system for iron phytosiderophores in roots of grasses.
Volker Römheld,Horst Marschner +1 more
TL;DR: The results indicate the existence of a specific uptake system for Fe(III)phytosiderophores in roots of barley and all other graminaceous species and two strategies are evident for the acquisition of iron by plants under iron deficiency.
Related Papers (5)
Regulation of nitrogenase activity by oxygen in Azospirillum brasilense and Azospirillum lipoferum.
A Hartmann,R H Burris +1 more