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Benjamin A Webb, K Karl Compton, Rafael Castañeda Saldaña, Timofey Arapov, W Keith Ray, Richard F Helm, Birgit E Scharf
The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine, and trigonelline. The wild type displayed a positive response to all QACs. Using LC-MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related non-host species, spotted medic (Medicago arabica), unique profiles were released...
October 17, 2016: Molecular Microbiology
Harald Marx, Catherine E Minogue, Dhileepkumar Jayaraman, Alicia L Richards, Nicholas W Kwiecien, Alireza F Sihapirani, Shanmugam Rajasekar, Junko Maeda, Kevin Garcia, Angel R Del Valle-Echevarria, Jeremy D Volkening, Michael S Westphall, Sushmita Roy, Michael R Sussman, Jean-Michel Ané, Joshua J Coon
Legumes are essential components of agricultural systems because they enrich the soil in nitrogen and require little environmentally deleterious fertilizers. A complex symbiotic association between legumes and nitrogen-fixing soil bacteria called rhizobia culminates in the development of root nodules, where rhizobia fix atmospheric nitrogen and transfer it to their plant host. Here we describe a quantitative proteomic atlas of the model legume Medicago truncatula and its rhizobial symbiont Sinorhizobium meliloti, which includes more than 23,000 proteins, 20,000 phosphorylation sites, and 700 lysine acetylation sites...
October 17, 2016: Nature Biotechnology
Andrew G Palmer, Arijit Mukherjee, Danielle M Stacy, Stephen Lazar, Jean-Michel Ané, Helen E Blackwell
Density-dependent phenotypic switching in bacteria, the phenomenon of quorum sensing (QS), is instrumental in many pathogenic and mutualistic behaviors. In many Gram-negative bacteria, QS is regulated by N-acylated-l-homoserine lactones (AHLs). Synthetic analogues of these AHLs hold significant promise for regulating QS at the host-symbiont interface. Regulation depends on refined temporal and spatial models of quorums under native conditions. Critical to this is an understanding of how the presence of these signals may affect a prospective host...
October 14, 2016: Chembiochem: a European Journal of Chemical Biology
Maria D Molina-Sánchez, Fernando M García-Rodríguez, Nicolás Toro
The functional unit of mobile group II introns is a ribonucleoprotein particle (RNP) consisting of the intron-encoded protein (IEP) and the excised intron RNA. The IEP has reverse transcriptase activity but also promotes RNA splicing, and the RNA-protein complex triggers site-specific DNA insertion by reverse splicing, in a process called retrohoming. In vitro reconstituted ribonucleoprotein complexes from the Lactococcus lactis group II intron Ll.LtrB, which produce a double strand break, have recently been studied as a means of developing group II intron-based gene targeting methods for higher organisms...
2016: Frontiers in Molecular Biosciences
Maryam Zamani, George C diCenzo, Branislava Milunovic, Turlough M Finan
We report that the smb20752 gene of the alfalfa symbiont Sinorhizobium meliloti is a novel symbiotic gene required for full N2 -fixation. Deletion of smb20752 resulted in lower nitrogenase activity and smaller nodules without impacting overall nodule morphology. Orthologs of smb20752 were present in all alpha and beta rhizobia, including the ngr_b20860 gene of Sinorhizobium fredii NGR234. A ngr_b20860 mutant formed Fix(-) determinate nodules that developed normally to a late stage of the symbiosis on the host plants Macroptillium atropurpureum and Vigna unguiculata...
October 11, 2016: Environmental Microbiology
Mengsheng Gao, Hanh T Nguyen, Isai Salas Gonzalez, Max Teplitski
The RNA-binding chaperone Hfq plays a critical role in the establishment and functionality of the symbiosis between Sinorhizobium meliloti and its legume hosts. A mutation in hfq reduces symbiotic efficiency resulting in a Fix- phenotype, characterized by the inability of the bacterium to fix nitrogen. At least in part, this is due to the ability of Hfq to regulate the fixLJ operon, which encodes a sensor kinase-response regulator pair that controls expression of the nitrogenase genes. The ability of Hfq to bind fixLJ in vitro and in planta was demonstrated with gel shift and co-immunoprecipitation experiments...
October 7, 2016: Molecular Plant-microbe Interactions: MPMI
Min Luo, Thameesha T Gamage, Benjamin W Arentson, Katherine N Schlasner, Donald F Becker, John J Tanner
Aldehyde dehydrogenases (ALDHs) catalyze the NAD(P)(+)-dependent oxidation of aldehydes to carboxylic acids and are important for metabolism and detoxification. Although the ALDH superfamily fold is well established, some ALDHs contain an uncharacterized domain of unknown function (DUF) near the C-terminus of the polypeptide chain. Herein, we report the first structure of a protein containing the ALDH superfamily DUF. Proline utilization A from Sinorhizobium meliloti (SmPutA) is a 1233-residue bifunctional enzyme that contains the DUF in addition to proline dehydrogenase and L-glutamate-γ-semialdehyde dehydrogenase catalytic modules...
September 27, 2016: Journal of Biological Chemistry
Masaru Bamba, Sayuri Nakata, Seishiro Aoki, Koji Takayama, Juan Núñez-Farfán, Motomi Ito, Masaki Miya, Tadashi Kajita
To understand the geographic distributions of rhizobia that associated with widely distributed wild legumes, 66 nodules obtained from 41 individuals including three sea-dispersed legumes (Vigna marina, Vigna luteola, and Canavalia rosea) distributed across the tropical and subtropical coastal regions of the world were studied. Partial sequences of 16S rRNA and nodC genes extracted from the nodules showed that only Bradyrhizobium and Sinorhizobium were associated with the pantropical legumes, and some of the symbiont strains were widely distributed over the Pacific...
September 23, 2016: Antonie Van Leeuwenhoek
Humberto Peralta, Alejandro Aguilar, Rafael Díaz, Yolanda Mora, Gabriel Martínez-Batallar, Emmanuel Salazar, Carmen Vargas-Lagunas, Esperanza Martínez, Sergio Encarnación, Lourdes Girard, Jaime Mora
BACKGROUND: Rhizobia are soil bacteria that establish symbiotic relationships with legumes and fix nitrogen in root nodules. We recently reported that several nitrogen-fixing rhizobial strains, belonging to Rhizobium phaseoli, R. trifolii, R. grahamii and Sinorhizobium americanum, were able to colonize Phaseolus vulgaris (common bean) seeds. To gain further insight into the traits that support this ability, we analyzed the genomic sequences and proteomes of R. phaseoli (CCGM1) and S. americanum (CCGM7) strains from seeds and compared them with those of the closely related strains CIAT652 and CFNEI73, respectively, isolated only from nodules...
2016: BMC Genomics
Rafael Nisa-Martínez, María Dolores Molina-Sánchez, Nicolás Toro
Bacterial group II introns are self-splicing catalytic RNAs and mobile retroelements that have an open reading frame encoding an intron-encoded protein (IEP) with reverse transcriptase (RT) and RNA splicing or maturase activity. Some IEPs carry a DNA endonuclease (En) domain, which is required to cleave the bottom strand downstream from the intron-insertion site for target DNA-primed reverse transcription (TPRT) of the inserted intron RNA. Host factors complete the insertion of the intron. By contrast, the major retrohoming pathway of introns with IEPs naturally lacking endonuclease activity, like the Sinorhizobium meliloti intron RmInt1, is thought to involve insertion of the intron RNA into the template for lagging strand DNA synthesis ahead of the replication fork, with possible use of the nascent strand to prime reverse transcription of the intron RNA...
2016: PloS One
Mohammed Shabab, Markus F F Arnold, Jon Penterman, Andrew J Wommack, Hartmut T Bocker, Paul A Price, Joel S Griffitts, Elizabeth M Nolan, Graham C Walker
Interactions of rhizobia with legumes establish the chronic intracellular infection that underlies symbiosis. Within nodules of inverted repeat-lacking clade (IRLC) legumes, rhizobia differentiate into nitrogen-fixing bacteroids. This terminal differentiation is driven by host nodule-specific cysteine-rich (NCR) peptides that orchestrate the adaptation of free-living bacteria into intracellular residents. Medicago truncatula encodes a family of >700 NCR peptides that have conserved cysteine motifs. NCR247 is a cationic peptide with four cysteines that can form two intramolecular disulfide bonds in the oxidized forms...
September 6, 2016: Proceedings of the National Academy of Sciences of the United States of America
F Pérez-Montaño, I Jiménez-Guerrero, S Acosta-Jurado, P Navarro-Gómez, F J Ollero, J E Ruiz-Sainz, F J López-Baena, J M Vinardell
Sinorhizobium fredii HH103 is a rhizobial soybean symbiont that exhibits an extremely broad host-range. Flavonoids exuded by legume roots induce the expression of rhizobial symbiotic genes and activate the bacterial protein NodD, which binds to regulatory DNA sequences called nod boxes (NB). NB drive the expression of genes involved in the production of molecular signals (Nod factors) as well as the transcription of ttsI, whose encoded product binds to tts boxes (TB), inducing the secretion of proteins (effectors) through the type 3 secretion system (T3SS)...
2016: Scientific Reports
Elizaveta Krol, Christina Klaner, Petra Gnau, Volkhard Kaever, Lars-Oliver Essen, Anke Becker
To identify physiological processes affected by cAMP in the plant-symbiotic nitrogen-fixing proteobacterium Sinorhizobium meliloti Rm2011, cAMP levels were artificially increased by overexpression of its cognate adenylate/guanylate cyclase gene cyaJ. This resulted in high accumulation of cAMP in the culture supernatant, decreased swimming motility and increased production of succinoglycan, an exopolysaccharide involved in host invasion. Weaker, similar phenotypic changes were induced by overexpression of cyaB and cyaG1...
August 16, 2016: Microbiology
Yohanna Sarria-Guzmán, Yosef Chávez-Romero, Selene Gómez-Acata, Joaquín Adolfo Montes-Molina, Eleacin Morales-Salazar, Luc Dendooven, Yendi E Navarro-Noya
Plant-associated microbes have specific beneficial functions and are considered key drivers for plant health. The bacterial community structure of healthy Anthurium andraeanum L. plants was studied by 16S rRNA gene pyrosequencing associated with different plant parts and the rhizosphere. A limited number of bacterial taxa, i.e., Sinorhizobium, Fimbriimonadales, and Gammaproteobacteria HTCC2089 were enriched in the A. andraeanum rhizosphere. Endophytes were more diverse in the roots than in the shoots, whereas all shoot endophytes were found in the roots...
September 29, 2016: Microbes and Environments
Annick Bertrand, Marie Bipfubusa, Catherine Dhont, François-P Chalifour, Pascal Drouin, Chantal J Beauchamp
Specific amino acids have protective functions in plants under stress conditions. This study assessed the effects of rhizobial strains on the amino acid composition in alfalfa under salt stress. Two alfalfa cultivars (Medicago sativa L. cv Apica and salt-tolerant cv Halo) in association with two Sinorhizobium meliloti strains with contrasting growth under salt stress (strain A2 and salt-tolerant strain Rm1521) were exposed to different levels of NaCl (0, 20, 40, 80 or 160 mM NaCl) under controlled conditions...
August 3, 2016: Plant Physiology and Biochemistry: PPB
Manel Chiboub, Omar Saadani, Imen Challougui Fatnassi, Souhir Abdelkrim, Ghassen Abid, Moez Jebara, Salwa Harzalli Jebara
The inoculation of plants with plant-growth-promoting rhizobacteria has become a priority in the phytoremediation of heavy-metal-contaminated soils. A total of 82 bacteria were isolated from Sulla coronaria root nodules cultivated on four soil samples differently contaminated by heavy metals. The phenotypic characterization of these isolates demonstrated an increased tolerance to cadmium reaching 4.1mM, and to other metals, including Zn, Cu and Ni. Polymerase Chain Reaction/Restriction Fragment Length Polymorphism (PCR/RFLP) analysis showed a large diversity represented by genera related to Agrobacterium sp...
September 2016: Comptes Rendus Biologies
Nicolás Toro, Francisco Martínez-Abarca, Manuel Fernández-López
BACKGROUND: Population genetic analyses based on genome-wide sequencing data have been carried out for Sinorhizobium medicae and S. meliloti, two closely related bacterial species forming nitrogen-fixing symbioses with plants of the genus Medicago. However, genome coverage was low or the isolates had a broad geographic distribution, making it difficult to interpret the estimated diversity and to unravel the early events underlying population genetic variations and ecological differentiation...
2016: BMC Genomics
Sebastián Acosta-Jurado, Pilar Navarro-Gómez, Piedad Del Socorro Murdoch, Juan-Carlos Crespo-Rivas, Shi Jie, Lidia Cuesta-Berrio, José-Enrique Ruiz-Sainz, Miguel-Ángel Rodríguez-Carvajal, José-María Vinardell
In the rhizobia-legume symbiotic interaction, bacterial surface polysaccharides, such as exopolysaccharide (EPS), lipopolysaccharide (LPS), K-antigen polysaccharide (KPS) or cyclic glucans (CG), appear to play crucial roles either acting as signals required for the progression of the interaction and/or preventing host defence mechanisms. The symbiotic significance of each of these polysaccharides varies depending on the specific rhizobia-legume couple. In this work we show that the production of exopolysaccharide by Sinorhizobium fredii HH103, but not by other S...
2016: PloS One
N A Provorov, E E Andronov
The processes of speciation and macroevolution of root nodule bacteria (rhizobia), based on deep rearrangements of their genomes and occurring in the N₂-fixing symbiotic system, are reconstructed. At the first stage of rhizobial evolution, transformation of free-living diazotrophs (related to Rhodopseudomonas) to symbiotic N₂-fixers (Bradyrhizobium) occurred due to the acquisition of the fix gene system, which is responsible for providing nitrogenase with electrons and reducing equivalents, as well as for oxygen-dependent regulation of nitrogenase synthesis in planta, and then of the nod genes responsible for the synthesis of the lipo- chito-oligosaccharide Nod factors, which induce root nodule development...
March 2016: Mikrobiologiia
Kata R Mikuláss, Krisztina Nagy, Balázs Bogos, Zsolt Szegletes, Etelka Kovács, Attila Farkas, György Váró, Éva Kondorosi, Attila Kereszt
BACKGROUND: Certain legume plants produce a plethora of AMP-like peptides in their symbiotic cells. The cationic subgroup of the nodule-specific cysteine-rich (NCR) peptides has potent antimicrobial activity against gram-negative and gram-positive bacteria as well as unicellular and filamentous fungi. FINDINGS: It was shown by scanning and atomic force microscopies that the cationic peptides NCR335, NCR247 and Polymyxin B (PMB) affect differentially on the surfaces of Sinorhizobium meliloti bacteria...
2016: Annals of Clinical Microbiology and Antimicrobials
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