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Journal ArticleDOI

Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants

TL;DR: A wide diversity of nitrogen-fixing bacterial species belonging to most phyla of the Bacteria domain have the capacity to colonize the rhizosphere and to interact with plants.
Abstract: Nitrogen is generally considered one of the major limiting nutrients in plant growth. The biological process responsible for reduction of molecular nitrogen into ammonia is referred to as nitrogen fixation. A wide diversity of nitrogen-fixing bacterial species belonging to most phyla of the Bacteria domain have the capacity to colonize the rhizosphere and to interact with plants. Leguminous and actinorhizal plants can obtain their nitrogen by association with rhizobia or Frankia via differentiation on their respective host plants of a specialized organ, the root nodule. Other symbiotic associations involve heterocystous cyanobacteria, while increasing numbers of nitrogen-fixing species have been identified as colonizing the root surface and, in some cases, the root interior of a variety of cereal crops and pasture grasses. Basic and advanced aspects of these associations are covered in this review.

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Citations
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Journal ArticleDOI
TL;DR: Features of the rhizosphere that are important for nutrient acquisition from soil are reviewed, with specific emphasis on the characteristics of roots that influence the availability and uptake of phosphorus and nitrogen.
Abstract: The rhizosphere is a complex environment where roots interact with physical, chemical and biological properties of soil. Structural and functional characteristics of roots contribute to rhizosphere processes and both have significant influence on the capacity of roots to acquire nutrients. Roots also interact extensively with soil microorganisms which further impact on plant nutrition either directly, by influencing nutrient availability and uptake, or indirectly through plant (root) growth promotion. In this paper, features of the rhizosphere that are important for nutrient acquisition from soil are reviewed, with specific emphasis on the characteristics of roots that influence the availability and uptake of phosphorus and nitrogen. The interaction of roots with soil microorganisms, in particular with mycorrhizal fungi and non-symbiotic plant growth promoting rhizobacteria, is also considered in relation to nutrient availability and through the mechanisms that are associated with plant growth promotion.

1,476 citations


Cites background from "Nitrogen-fixing bacteria associated..."

  • ...For rhizobia and Frankia this involves symbiotic relationships with host legume and actinorhizal plants, respectively (see review by Franche et al. 2009), and are therefore not considered here....

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  • ...Rhizobia develop symbiotic relationships with host legumes and through atmospheric N2 fixation within nodules can provide up to 90% of the N requirements of the plant (see Franche et al. 2009; Höflich et al. 1994)....

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Journal ArticleDOI
TL;DR: It is surmised that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.
Abstract: There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (P<0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.

987 citations


Cites background from "Nitrogen-fixing bacteria associated..."

  • ...…or Burkholderia ambifaria (Chiarini et al., 2006), free N-fixers such as Cyanothece sp. (Junier et al., 2009), as well as symbiotic N-fixing bacteria (Bradyrhizobium) (Stacey et al., 1995) or Herbaspirillum which is involved in endophytic N fixation (Elbeltagy et al., 2001; Franche et al., 2009)....

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  • ...Cyanobacteria have been shown to colonize plant roots (Gantar et al., 1991; Lundberg et al., 2012), promote plant growth (Prasanna et al., 2009) and are an important plant source for inorganic N due to their ability to fix N (Franche et al., 2009)....

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  • ..., 2009) and are an important plant source for inorganic N due to their ability to fix N (Franche et al., 2009)....

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  • ..., 1995) or Herbaspirillum which is involved in endophytic N fixation (Elbeltagy et al., 2001; Franche et al., 2009)....

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Journal ArticleDOI
TL;DR: In this article, the authors evaluate competitive and mutualistic interactions between plants and microorganisms and analyse the ecological consequences of these interactions in the rhizosphere, and they find that despite strong competition between roots and micro-organisms for N, a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the root network.
Abstract: Demand of all living organisms on the same nutrients forms the basis for interspecific competition between plants and microorganisms in soils. This competition is especially strong in the rhizosphere. To evaluate competitive and mutualistic interactions between plants and microorganisms and to analyse ecological consequences of these interactions, we analysed 424 data pairs from 41 (15)N-labelling studies that investigated (15)N redistribution between roots and microorganisms. Calculated Michaelis-Menten kinetics based on K(m) (Michaelis constant) and V(max) (maximum uptake capacity) values from 77 studies on the uptake of nitrate, ammonia, and amino acids by roots and microorganisms clearly showed that, shortly after nitrogen (N) mobilization from soil organic matter and litter, microorganisms take up most N. Lower K(m) values of microorganisms suggest that they are especially efficient at low N concentrations, but can also acquire more N at higher N concentrations (V(max)) compared with roots. Because of the unidirectional flow of nutrients from soil to roots, plants are the winners for N acquisition in the long run. Therefore, despite strong competition between roots and microorganisms for N, a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the rhizosphere. This temporal niche differentiation is highly relevant ecologically because it: protects ecosystems from N losses by leaching during periods of slow or no root uptake; continuously provides roots with available N according to plant demand; and contributes to the evolutionary development of mutualistic interactions between roots and microorganisms.

858 citations

Journal ArticleDOI
TL;DR: There is a gap between the mode of action (mechanism) of the PGPR for plant growth and the role of thePGPR as biofertilizer—thus the importance of nano-encapsulation technology in improving the efficacy of PGPR is highlighted.
Abstract: Plant growth promoting rhizobacteria (PGPR) shows an important role in the sustainable agriculture industry. The increasing demand for crop production with a significant reduction of synthetic chemical fertilizers and pesticides use is a big challenge nowadays. The use of PGPR has been proven to be an environmentally sound way of increasing crop yields by facilitating plant growth through either a direct or indirect mechanism. The mechanisms of PGPR include regulating hormonal and nutritional balance, inducing resistance against plant pathogens, and solubilizing nutrients for easy uptake by plants. In addition, PGPR show synergistic and antagonistic interactions with microorganisms within the rhizosphere and beyond in bulk soil, which indirectly boosts plant growth rate. There are many bacteria species that act as PGPR, described in the literature as successful for improving plant growth. However, there is a gap between the mode of action (mechanism) of the PGPR for plant growth and the role of the PGPR as biofertilizer—thus the importance of nano-encapsulation technology in improving the efficacy of PGPR. Hence, this review bridges the gap mentioned and summarizes the mechanism of PGPR as a biofertilizer for agricultural sustainability.

787 citations


Cites background from "Nitrogen-fixing bacteria associated..."

  • ...The PGPM can be classified into three dominant groups of microorganisms: arbuscular mycorrhizal fungi (AMF) [107], plant growth promoting rhizobacteria (PGPR) [108], and nitrogen fixing rhizobia [109], which are deemed to be beneficial to plant growth and nutrition....

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Journal ArticleDOI
TL;DR: The key mechanisms involved in plant stress tolerance and the effectiveness of microbial inoculation for enhancing plant growth under stress conditions have been discussed at length in this review.

727 citations


Cites background from "Nitrogen-fixing bacteria associated..."

  • ...…enhances due to growth promotion mechanisms used by microbes such as production of phytohormones, suppressing of pathogens, nitrogen fixation and solubilization of minerals (Ahmad et al., 2008; Bootkotr and Mongkolthanaruk, 2012; Franche et al., 2009; Hayat et al., 2010; Saharan and Nehra, 2011)....

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  • ...The interactions may take place between plant and fungus/bacteria in which both partners get benefits as mutualistic association (Beattie, 2007; Finlay, 2007) and ultimately plant growth enhances due to growth promotion mechanisms used by microbes such as production of phytohormones, suppressing of pathogens, nitrogen fixation and solubilization of minerals (Ahmad et al., 2008; Bootkotr and Mongkolthanaruk, 2012; Franche et al., 2009; Hayat et al., 2010; Saharan and Nehra, 2011)....

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References
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Journal ArticleDOI
TL;DR: Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification, and are both constant and readily determinable in cultured material.
Abstract: Summary: On the basis of a comparative study of 178 strains of cyanobacteria, representative of this group of prokaryotes, revised definitions of many genera are proposed. Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification. The differential characters proposed are both constant and readily determinable in cultured material. The 22 genera recognized are placed in five sections, each distinguished by a particular pattern of structure and development. Generic descriptions are accompanied by strain histories, brief accounts of strain properties, and illustrations; one or more reference strains are proposed for each genus. The collection on which this analysis was based has been deposited in the American Type Culture Collection, where strains will be listed under the generic designations proposed here.

7,107 citations


"Nitrogen-fixing bacteria associated..." refers background in this paper

  • ...Long regarded as algae because they performed oxygenic photosynthesis, they are now classified into the domain of Bacteria, in five Sections based mostly on morphological criteria (Rippka et al. 1979)....

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  • ...Nostoc hrmA mutants are unable to survive in long-term coculture with Anthoceros due to their continued formation of hormogonia....

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  • ...Then, compatible Nostoc strains induce divisions in the host cells lining the channel and Nostoc cells are subsequently taken up into plant cells....

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  • ...Symbiotic associations with vascular plants Gunnera, a genus of about 40 species, is the only angiosperm with which the cyanobacterium referred to as Nostoc punctiforme is associated (Rasmussen and Svenning 2001)....

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  • ...In contrast, wild-type filaments of Nostoc spp., after an initial burst of HIF-induced hormogonia formation, show a period of immunity to HIF enabling growth and nitrogen fixation....

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Journal ArticleDOI
TL;DR: Highlights in biological nitrogen fixation during the last fifty years are highlighted.
Abstract: Biological nitrogen fixation (BNF) is the process of the reduction of dinitrogen from the air to ammonia carried out by a large number of species of free-living and symbiotic microbes called diazotrophs. BNF presents an inexpensive and environmentally sound, sustainable approach to crop production and constitutes one of the most important Plant Growth Promotion (PGP) scenarios. Here I will summarize various aspects of BNF, including the dinitrogen reduction catalysed reaction carried out by “nitrogenase” and the enzymes/genes involved and their regulation, the inherent “oxygen paradox” , the identification of diazotrophs, sustainable agricultural uses of BNF, symbiotic plant-diazotroph interactions and endophytic diazotrophs, data from the field, and future prospects in BNF.

1,512 citations

Journal ArticleDOI
TL;DR: The biochemical basis of the assay is described along with relevant characteristics including Km, C2H2/N2 conversion factor, and specific N2[C2H 2]-fixing activities obtained with various systems, and methods of measurement of N2 fixation are compared.
Abstract: A comprehensive report of the acetylene reduction assay for measurement of N2 fixation is presented. The objective is to facilitate the effective use and identify some potential limitations of the method. The report is based on more than 200 accounts of the use of this technique in 15 countries during the last 5 years. Methods of measurement of N2 fixation are compared. Nomenclature, e.g., N2[C2H2] fixed, is introduced to identify values of N2 fixation determined by C2H2-C2H2 assay. The biochemical basis of the assay is described along with relevant characteristics including Km, C2H2/N2 conversion factor, and specific N2[C2H2]-fixing activities obtained with various systems. Effects of combined nitrogen, temperature, light, pO2, N2, pC2H2 and water on activity are summarized. Available methods for sample preparation, assay chamber, gas phase, assay condition, termination of reaction, C2H4 analysis and expression of results are compared. The many uses of the C2H2-C2H4 assay for investigations of the biochemistry of nitrogenase and physiology of N2-fixing organisms, definition of N2-fixing organisms and measurement of field N2 fixation by legume, non-legume, soil, marine, rhizosphere, phylloplane and mammalian samples are tabulated.

1,021 citations


"Nitrogen-fixing bacteria associated..." refers methods in this paper

  • ...A major achievement for rapid determination of nitrogenase activity was the development of an assay using the acetylene reduction technique (Hardy et al. 1973), which could be applied not only to pure cultures and cellular extracts, but also to excised roots, soil cores and greenhouse experiments…...

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Journal ArticleDOI
TL;DR: This review focuses on the tissue-specific nature of the developmental processes associated with nodulation and the mechanisms by which these processes are coordinated during the formation of a nodule.
Abstract: The formation of nitrogen-fixing nodules on legumes requires an integration of infection by rhizobia at the root epidermis and the initiation of cell division in the cortex, several cell layers away from the sites of infection. Several recent developments have added to our understanding of the signaling events in the epidermis associated with the perception of rhizobial nodulation factors and the role of plant hormones in the activation of cell division leading to nodule morphogenesis. This review focuses on the tissue-specific nature of the developmental processes associated with nodulation and the mechanisms by which these processes are coordinated during the formation of a nodule.

1,003 citations


"Nitrogen-fixing bacteria associated..." refers background in this paper

  • ...Further steps in the signalling cascade lead to induction of cortical cell division (Limpens and Bisseling 2003; Kinkema et al. 2006; Oldroyd and Downie 2008)....

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Journal ArticleDOI
TL;DR: The ability of microorganisms to use nitrogen gas as the sole nitrogen source and engage in symbioses with host plants confers many ecological advantages, but also incurs physiological penalties because the process is oxygen sensitive and energy dependent.
Abstract: Some bacteria have the remarkable capacity to fix atmospheric nitrogen to ammonia under ambient conditions, a reaction only mimicked on an industrial scale by a chemical process that requires high temperatures, elevated pressure and special catalysts. The ability of microorganisms to use nitrogen gas as the sole nitrogen source and engage in symbioses with host plants confers many ecological advantages, but also incurs physiological penalties because the process is oxygen sensitive and energy dependent. Consequently, biological nitrogen fixation is highly regulated at the transcriptional level by sophisticated regulatory networks that respond to multiple environmental cues.

979 citations


"Nitrogen-fixing bacteria associated..." refers background in this paper

  • ...well as the regulatory nifLA genes controlling expression of the nif cluster (Merrick and Edwards 1995; Dixon and Kahn 2004)....

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  • ...which the nitrogen fixation process can operate (for details see Fischer 1994; Dixon and Kahn 2004; Pedrosa and Elmerich, 2007)....

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  • ...…rnfABCDGEF cluster) to nitrogenase, molybdenum uptake and homeostasis, and oxygen protection and regulation, including respiratory chains adapted to oxygen conditions at which the nitrogen fixation process can operate (for details see Fischer 1994; Dixon and Kahn 2004; Pedrosa and Elmerich, 2007)....

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  • ...In addition, Klebsiella contains genes required for electron transport to nitrogenase (nifF and nifJ), as well as the regulatory nifLA genes controlling expression of the nif cluster (Merrick and Edwards 1995; Dixon and Kahn 2004)....

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