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The Genetics of the Frankia-Actinorhizal Symbiosis
Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018
Pascal Simonet, Philippe Normand, Ann M. Hirsch, Antoon D. L. Akkermans
The process of biological nitrogen fixation which is carried out by a number of prokaryotic organisms via the nitrogenase enzyme complex remains rate-limiting in many agricultural areas. There has been much discussion about improving biological nitrogen fixation, especially the Rhizobium-legume symbiosis which is the best known. However, many other symbiotic associations occur, and these have been recently reviewed.1,2 Symbiosis between woody, dicotyledonous plants and Frankia, a filamentous prokaryote which is classified in the order Actinomycetales,3 is particularly interesting, and several reviews have been published recently that describe in detail various aspects of the Frankia-actinorhizal plant symbiosis. These include the biology of Frankia,4 the efficiency of the nitrogen-fixing activity of the actinorhizal association,5 the ecology,6 host plant-endophyte specificity, and the genetics of Frankia.7 The progress in Frankia-actinorhizal plant symbiosis has been presented in the proceedings of symposia on this subject during the last decade: Petersham,8 Corvallis,9 Madison,10 Wageningen,11 Laval,12 and Umeå.13
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].
Graphene oxide influence in soil bacteria is dose dependent and changes at osmotic stress: growth variation, oxidative damage, antioxidant response, and plant growth promotion traits of a Rhizobium strain
Published in Nanotoxicology, 2022
Tiago Lopes, Paulo Cardoso, Diana Matos, Ricardo Rocha, Adília Pires, Paula Marques, Etelvina Figueira
Plant growth-promoting rhizobacteria (PGPR) are an important group of bacteria that can help boost plant productivity and mitigate drought effects (Ahemad and Kibret 2014; Lugtenberg and Kamilova 2009). PGPR possesses several capabilities of plant growth promotion, such as the production of indole acetic acid, which promotes the development of lateral roots (Ahemad and Kibret 2014), biological nitrogen fixation, increasing the amount of nitrogen present in soil (Ahemad and Kibret 2014), production of siderophores that increases iron availability for plants, as well for bacteria (Ahemad and Kibret 2014), or solubilization and mineralization of phosphate that increases the availability of phosphorus for plants (Goswami, Thakker, and Dhandhukia 2016). Environments with low water potentials can cause cell water efflux, leading to an increase in metabolites concentration in the cytoplasm (Paul 2013). Some of these metabolites are toxic to cells and their increased concentration due to water loss can affect cell metabolism (Wood 2011). To survive and be able to proliferate in environments with low water potentials, cells must regulate osmotically by producing compatible solutes (Brown and Simpson 1972). Solutes like glycine betaine, able to maintain an equivalent osmolarity between the cell and the medium (Larsen et al. 1987; Freeman et al. 2013), or alginate, that preserve membrane integrity and provide a competitive advantage in water-limited environments (Chang et al. 2007; Bérard et al. 2015; Welsh 2000), were reported as the parameters that best explained the osmotic tolerance levels displayed by soil bacteria (Sá, Cardoso, and Figueira 2019). However, these mechanisms are metabolically and energetically costly, reducing resources for bacterial growth (Wichern, Wichern, and Joergensen 2006; Schimel, Balser, and Wallenstein 2007), and with poorly known consequences for their PGP abilities.