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Nodulation and nitrogen fixation

Kent N Strodtman, Sooyoung Frank, Severin Stevenson, Jay J Thelen, David W Emerich
The form and physiology of Bradyrhizobium diazoefficiens after the decline of symbiotic nitrogen fixation has been characterized. Proteomic analyses showed that post-symbiotic B. diazoefficiens underwent metabolic remodeling as well-defined groups of proteins declined, increased or remained unchanged from 56 to 119 days after planting, suggesting a transition to a hemibiotrophic-like lifestyle. Enzymatic analysis showed distinct patterns in both the cytoplasm and the periplasm. Similar to the bacteroid, the post-symbiotic bacteria rely on a non-citric acid cycle supply of succinate and, although viable, they did not demonstrate the ability to grow within the senescent nodule...
December 8, 2018: International Journal of Molecular Sciences
Juan Liang, Anne Hoffrichter, Andreas Brachmann, Macarena Marín
Rhizobia bacteria engage in nitrogen-fixing root nodule symbiosis, a mutualistic interaction with legume plants in which a bidirectional nutrient exchange takes place. Occasionally, this interaction is suboptimal resulting in the formation of ineffective nodules in which little or no atmospheric nitrogen fixation occurs. Rhizobium leguminosarum Norway induces ineffective nodules in a wide range of Lotus hosts. To investigate the basis of this phenotype, we sequenced the complete genome of Rl Norway and compared it to the genome of the closely related strain R...
2018: Standards in Genomic Sciences
Hai D T Nguyen, Sylvie Cloutier, Eden S P Bromfield
We present the complete genome sequence of Bradyrhizobium ottawaense strain OO99T , a nitrogen-fixing bacterium from root nodules of soybean. The genome consists of a single 8.6-Mb chromosome and includes a symbiosis island. Genes involved in symbiotic nitrogen fixation, stress response, resistance to antibiotics, and toxic compounds were detected.
November 2018: Microbiology resource announcements
Alejandrina Hernández-López, Mauricio Díaz, Jonathan Rodríguez-López, Gabriel Guillén, Federico Sánchez, Claudia Díaz-Camino
Bax-inhibitor 1 (BI-1) is a cell death suppressor conserved in all eukaryotes that modulates cell death in response to abiotic stress and pathogen attack in plants. Thus far nothing is known about its role in the establishment of symbiotic interactions. Here, we demonstrate the functional relevance of an Arabidopsisthaliana BI-1 homolog (PvBI-1a) to symbiosis between the common bean (Phaseolus vulgaris) and Rhizobium tropici. We show that the PvBI-1a expression changes observed during early symbiosis resemble those of some defence-response related proteins...
November 21, 2018: Journal of Experimental Botany
Sebastian Schneider, Arno Schintlmeister, Manuel Becana, Michael Wagner, Dagmar Woebken, Stefanie Wienkoop
Legume-rhizobia symbioses play a major role in food production for an ever growing human population. In this symbiosis, dinitrogen is reduced ('fixed') to ammonia by the rhizobial nitrogenase enzyme complex and is secreted to the plant host cells, while dicarboxylic acids derived from photosynthetically-produced sucrose are transported into the symbiosomes and serve as respiratory substrates for the bacteroids. The symbiosome membrane contains high levels of SST1 protein, a sulfate transporter. Sulfate is an essential nutrient for all living organisms, but its importance for symbiotic nitrogen fixation and nodule metabolism has long been underestimated...
November 15, 2018: Plant, Cell & Environment
Manisha Shrestha, Karl K Compton, Jordan Mancl, Benjamin Webb, Anne Brown, Birgit Scharf, Florian D Schubot
The alpha-proteobacterium Sinorhizobium meliloti can live freely in the soil or engage in a symbiosis with its legume host.  S. meliloti facilitates nitrogen-fixation in root nodules, thus providing pivotal, utilizable nitrogen to the host.  The organism has eight chemoreceptors, namely McpT to McpZ and IcpA that facilitate chemotaxis.  McpX is the first known bacterial sensor of quaternary amine compounds (QACs) such as choline and betaines.  Because QACs are exuded at chemotaxis-relevant concentrations by germinating alfalfa seeds, McpX has been proposed to contribute to host-specific chemotaxis...
November 15, 2018: Biochemical Journal
Fanuel Kawaka, Huxley Makonde, Mathews Dida, Peter Opala, Omwoyo Ombori, John Maingi, John Muoma
Biological nitrogen fixation (BNF) in legumes plays a critical role in improving soil fertility. Despite this vital role, there is limited information on the genetic diversity and BNF of bacteria nodulating common bean (Phaseolus vulgaris L.). This study evaluated the genetic diversity and symbiotic nitrogen fixation of bacteria nodulating common bean in soils of Western Kenya. The genetic diversity was determined using 16S rRNA gene partial sequences while BNF was estimated in a greenhouse experiment. The sequences of the native isolates were closely affiliated with members from the genera Pantoea, Klebsiella, Rhizobium, Enterobacter and Bacillus...
2018: PloS One
Drishti Mandal, Senjuti Sinharoy
Mesorhizobium sp. produces root nodules in chickpea. Chickpea and model legume Medicago truncatula are members of inverted repeat lacking clade (IRLC). The rhizobia after internalization into the plant cell are called 'bacteroid'. Nodule Specific Cysteine-rich (NCR) peptides in IRLC legumes guide bacteroids to a 'terminally differentiated swollen (TDS)' form. Bacteroids in chickpea are less TDS than those in Medicago. Nodule development in chickpea indicates recent evolutionary diversification and merits further study...
November 6, 2018: Molecular Plant-microbe Interactions: MPMI
Manuel Becana, Stefanie Wienkoop, Manuel A Matamoros
Sulfur is an essential nutrient in plants as a constituent element of some amino acids, metal cofactors, coenzymes, and secondary metabolites. Not surprisingly, sulfur deficiency decreases plant growth, photosynthesis, and seed yield in both legumes and non-legumes. In nodulated legumes, sulfur supply is positively linked to symbiotic nitrogen fixation (SNF) and sulfur starvation causes three additional major effects: decrease of nodulation, inhibition of SNF, and slowing down of nodule metabolism. These effects are due, at least in part, to the impairment of nitrogenase biosynthesis and activity, the accumulation of nitrogen-rich amino acids, and the decline in leghemoglobin, ferredoxin, ATP, and glucose in nodules...
2018: Frontiers in Plant Science
K S Antonets, O P Onishchuk, O N Kurchak, K V Volkov, A N Lykholay, E A Andreeva, E E Andronov, A G Pinaev, N A Provorov, A A Nizhnikov
The importance of root nodule bacteria in biotechnology is determined by their distinctive feature: symbiotic nitrogen fixation resulting in the production of organic nitrogen-containing compounds. While interacting with host legume plants, the cells of these bacteria undergo global changes at all levels of expression of genetic information leading to the formation in root nodules of so-called bacteroids functioning as nitrogen fixation factories. The molecular mechanisms underlying plant-microbial symbiosis are actively investigated, and one of the most interesting and poorly studied aspects of this problem is the species-specificity of interaction between root nodule bacteria and host plants...
September 2018: Molekuliarnaia Biologiia
Brendan Epstein, Reda A I Abou-Shanab, Abdelaal Shamseldin, Margaret R Taylor, Joseph Guhlin, Liana T Burghardt, Matthew Nelson, Michael J Sadowsky, Peter Tiffin
Genome-wide association studies (GWAS) can identify genetic variants responsible for naturally occurring and quantitative phenotypic variation. Association studies therefore provide a powerful complement to approaches that rely on de novo mutations for characterizing gene function. Although bacteria should be amenable to GWAS, few GWAS have been conducted on bacteria, and the extent to which nonindependence among genomic variants (e.g., linkage disequilibrium [LD]) and the genetic architecture of phenotypic traits will affect GWAS performance is unclear...
October 24, 2018: MSphere
Shogo Nishihata, Takahiko Kondo, Kosei Tanaka, Shu Ishikawa, Shinji Takenaka, Choong-Min Kang, Ken-Ichi Yoshida
BACKGROUND: Bradyrhizobium diazoefficiens USDA110 nodulates soybeans for nitrogen fixation. It accumulates poly-3-hydroxybutyrate (PHB), which is of physiological importance as a carbon/energy source for survival during starvation, infection, and nitrogen fixation conditions. PHB accumulation is orchestrated by not only the enzymes for PHB synthesis but also PHB-binding phasin proteins (PhaPs) stabilizing the PHB granules. The transcription factor PhaR controls the phaP genes. RESULTS: Inactivation of phaR led to decreases in PHB accumulation, less cell yield, increases in exopolysaccharide (EPS) production, some improvement in heat stress tolerance, and slightly better growth under microaerobic conditions...
October 24, 2018: BMC Microbiology
Joy B Winbourne, Matt T Harrison, Ben W Sullivan, Silvia Alvarez-Clare, Silvia R Lins, Luiz Martinelli, Megan Nasto, Daniel Piotto, Samir Rolim, Michelle Wong, Stephen Porder
Symbiotic nitrogen fixation (SNF) makes atmospheric nitrogen biologically available and regulates carbon storage in many terrestrial ecosystems. Despite its global importance, estimates of SNF rates are highly uncertain, particularly in tropical forests where rates are assumed to be high. Here we provide a framework for evaluating the uncertainty of sample-based SNF estimates and discuss its implications for quantifying SNF and thus understanding of forest function. We apply this framework to field data sets from six lowland tropical rainforests (mature and secondary) in Brazil and Costa Rica...
November 2018: American Naturalist
William P Buhian, Sandra Bensmihen
The rhizobia-legume symbiosis is a mutualistic association in which bacteria provide plants with nitrogen compounds and the plant provides bacteria with carbon sources. A successful symbiotic interaction relies on a molecular dialog between the plant and the bacteria, and generally involves rhizobial lipo-chitooligosaccharide signals called Nod factors (NFs). In most cases, specific NF perception is required for rhizobia to enter root cells through newly formed intracellular structures called infection threads (ITs)...
2018: Frontiers in Plant Science
Liyu Chen, Lu Qin, Lili Zhou, Xinxin Li, Zhichang Chen, Lili Sun, Wenfei Wang, Zhihao Lin, Jing Zhao, Naoki Yamaji, Jian Feng Ma, Mian Gu, Guohua Xu, Hong Liao
Symbiotic nitrogen (N2 ) fixation plays a vital role in sustainable agriculture. Efficient N2 fixation requires various materials, including phosphate (Pi); however, the molecular mechanism underlying the transport of Pi into nodules and bacteroids remains largely unknown. A nodule-localized Pi transporter, GmPT7, was functionally characterized in soybean (Glycine max) and its role in N2 fixation and yield was investigated via composite and whole transgenic plants. GmPT7 protein was localized to the plasma membrane and showed transport activity for Pi in yeast...
October 14, 2018: New Phytologist
Claus Lang, Melanie J Barnett, Robert F Fisher, Lucinda S Smith, Michelle E Diodati, Sharon R Long
Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner...
October 10, 2018: MSphere
Guy Dovrat, Efrat Sheffer
Plants, especially perennials, growing in drylands and seasonally dry ecosystems are uniquely adapted to dry conditions. Legume shrubs and trees, capable of symbiotic dinitrogen (N2 ) fixation, often dominate in drylands. However, the strategies that allow symbiotic fixation in these ecosystems, and their influence on the nitrogen cycle, are largely unresolved. We evaluated the climatic, biogeochemical and ontogenetic factors influencing nitrogen fixation in an abundant Mediterranean legume shrub, Calicotome villosa...
October 9, 2018: New Phytologist
Jie-Shun Lin, Xiaolin Li, Zhenpeng Luo, Kirankumar S Mysore, Jiangqi Wen, Fang Xie
Legume plants can assimilate inorganic nitrogen and have access to fixed nitrogen through symbiotic interaction with diazotrophic bacteria called rhizobia. Symbiotic nitrogen fixation is an energy-consuming process and is strongly inhibited when sufficient levels of fixed nitrogen are available, but the molecular mechanisms governing this regulation are largely unknown. The transcription factor nodule inception (NIN) is strictly required for nodulation and belongs to a family of NIN-like proteins (NLPs), which have been implicated in the regulation of nitrogen homeostasis in Arabidopsis...
November 2018: Nature Plants
Mustapha Mohammed, Sanjay K Jaiswal, Elias N K Sowley, Benjamin D K Ahiabor, Felix D Dakora
Kersting's groundnut ( Macrotyloma geocarpum Harms) is a neglected, endangered food and medicinal legume in Africa. Efforts to harness the benefits of the legume-rhizobia symbiosis have focused on few major legumes to the neglect of underutilized ones such as Kersting's groundnut. This study assessed plant growth, N-fixed and grain yield of five Kersting's groundnut landraces in response to inoculation with Bradyrhizobium strain CB756 at two locations in the Northern Region of Ghana. The transferability of cowpea-derived Simple Sequence Repeat (SSR) markers to Kersting's groundnut was also assessed...
2018: Frontiers in Microbiology
Amalia Soenens, Margarita Gomila, Juan Imperial
We describe for the first time a non-symbiotic species of the recently described genus Neorhizobium, lacking nodulation or nitrogen fixation genes. The strains were isolated from a dryland agricultural soil in southern Spain where no record of legume cultivation is available, thus we propose the name Neorhizobium tomejilense sp. nov. (type strain T17_20T , LMG 30623T and CECT 9621T ). N. tomejilense exhibit a clear distinct lineage from the other Neorhizobium species, Neorhizobium galegae, Neorhizobium alkalisoli and Neorhizobium huautlense, based on polyphasic evidence...
September 17, 2018: Systematic and Applied Microbiology
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