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Legumes
Published in Christopher Cumo, Ancestral Diets and Nutrition, 2020
Egyptians and Romans observed that legumes improved soil fertility without understanding why. In 1886, German chemists Hermann Hellriegel (1831–1895) and Hermann Wilfarth (1853–1904) supplied the answer by describing nitrogen fixation.7Rhizobium bacteria and legumes interact symbiotically. The bacteria infect legume root filaments, known as hairs, forming nodules. Nodules shelter these bacteria, which convert the soil’s nitrogen gas (N2) into ammonium cations (NH4+). Plants, and in turn herbivores and omnivores, depend on this transformation because roots cannot absorb nitrogen gas but can take up ions as nourishment. Ammonium benefits not only legumes. Unabsorbed surplus remains available for next year’s crops.
Chemical Structure of the Core Region of Lipopolysaccharides
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Bacteria of the genera Rhizobium and Bradyrhizobium live in symbiosis with legume plants and participate in the process of nitrogen assimilation. Several partial core structures of LPS from R. leguminisarum, R. meliloti, and B. japonicum have been published (Table 9) (219, 226). The core structure of R. etli CE3 comprises two oligosaccharides, which have also been isolated from R. leguminisarum bv. trifolii strains ANU843 and 24.1, a branched tetrasaccharide consisting of Gal, Man, GalA, and Kdo, which is substituted at 0–4 of Kdo by a branched trisaccharide built up from two GalA and one Kdo residues (226,227). In both species, the O-antigen is linked to O-6 of the Gal residue of the tetrasaccharide unit, and in the core of R. etli this is furnished via a third Kdo residue. The anomeric configuration of the Kdo residues are not published.
The Rhizobium/Bradyrhizobium-Legume Symbiosis
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Gene clusters — Symbiotic genes tend to be more closely clustered in Rhizobium (at least in the temperate Rhizobium strains, R. leguminosarum, R. trifolii, and R. meliloti) than in Brady rhizobium. For example, the nifH nifD nifK genes form a single operon in Rhizobium but are present in two widely separated operons (nifH and nifD nifK) in Bradyrhizobium.
Insights in nodule-inhabiting plant growth promoting bacteria and their ability to stimulate Vicia faba growth
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Amr M. Mowafy, Mona S. Agha, Samia A. Haroun, Mohamed A. Abbas, Mohamed Elbalkini
Symbiotic nitrogen fixation, which is positioned as a major part of biological nitrogen fixation, is an important alternative source of chemical nitrogen fertilizers not only for leguminous but also for non-leguminous plants. The interaction between legumes and rhizobia leads to root nodule organogenesis, an organ that is produced in response to bacterial nod factors and plant developmental signals leading to the formation of a plant stem cell niche [1]. Recently, rhizobia have been shown to improve the nutrition of non-leguminous crops, such as barley, wheat and canola [2]. It has been established that the legume nodule is exclusively inhabited by the rhizobium. Meanwhile, in 2001, this concept has changed dramatically when non-rhizobial strains were regarded for their ability to nodulate legumes, such as Methylobacterium and Burkholderia that have been isolated from Crotalaria [3] and Mimosa [4], respectively. In addition to nodule-inducing bacteria, several bacterial strains have been isolated from nodules as co-inhabitants with rhizobium, such as Klebsiella, Pseudomonas [5], Bacillus [6] and Streptomyces [7]. Interestingly, a review titled ‘the nodule microbiome: N2-fixing rhizobia do not live alone’ has been published in 2017 to conclude that some of these non-rhizobial bacteria might be nitrogen fixer or participate in nodule genesis and the others, more striking, might neither participate in nodulation nor fix nitrogen [8].
Nanotoxicity of engineered nanomaterials (ENMs) to environmentally relevant beneficial soil bacteria – a critical review
Published in Nanotoxicology, 2019
Ricky W. Lewis, Paul M. Bertsch, David H. McNear
Sinorhizobium meliloti is a soil bacterium capable of fixing N2 through a symbiotic relationship with plant species from the Medicago, Melilotus, and Trigonella genera (Roumiantseva et al. 2002). The symbiosis between Si. meliloti and the model legume, Medicago truncatula, is currently being exploited to dissect the biochemical and molecular mechanisms of the legume symbiosis and much more. The plant growth-promoting abilities of Si. meliloti in non-leguminous plants (lettuce) have been known for some time now (Galleguillos et al. 2000), but the mechanism remains obscured. Some strains of rhizobia have been shown to exhibit ACC deaminase activity which may lead to plant growth promoting activities, but it is not thought that Si. meliloti 1021 possesses the ACC deaminase gene (Ma et al. 2003).