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Wen Xin Chen - One of the best experts on this subject based on the ideXlab platform.
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Replicon-Dependent Differentiation of Symbiosis-Related Genes in Sinorhizobium Strains Nodulating Glycine max
Applied and Environmental Microbiology, 2013Co-Authors: Hui Juan Guo, En Tao Wang, Xing Xing Zhang, Yan Ming Zhang, Chang Fu Tian, Wen Xin ChenAbstract:In order to investigate the genetic differentiation of Sinorhizobium strains nodulating Glycine max and related microevolutionary mechanisms, three housekeeping genes (SMc00019, truA, and thrA) and 16 symbiosis-related genes on the chromosome (7 genes), pSymA (6 genes), and pSymB (3 genes) were analyzed. Five distinct species were identified among the test strains by calculating the average nucleotide identity (ANI) of SMc00019-truA-thrA: Sinorhizobium fredii, Sinorhizobium sojae, Sinorhizobium sp. I, Sinorhizobium sp. II, and Sinorhizobium sp. III. These species assignments were also supported by population genetics and phylogenetic analyses of housekeeping genes and symbiosis-related genes on the chromosome and pSymB. Different levels of genetic differentiation were observed among these species or different replicons. S. sojae was the most divergent from the other test species and was characterized by its low intraspecies diversity and limited geographic distribution. Intergenic recombination dominated the evolution of 19 genes from different replicons. Intraspecies recombination happened frequently in housekeeping genes and symbiosis-related genes on the chromosome and pSymB, whereas pSymA genes showed a clear pattern of lateral-transfer events between different species. Moreover, pSymA genes were characterized by a lower level of polymorphism and recombination than those on the chromosome and pSymB. Taken together, genes from different replicons of rhizobia might be involved in the establishment of symbiosis with legumes, but these symbiosis-related genes might have evolved differently according to their corresponding replicons.
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Identification of isolates from soybean nodules in Xinjiang Region as Sinorhizobium xinjiangense and genetic differentiation of S. xinjiangense from Sinorhizobium fredii.
International Journal of Systematic and Evolutionary Microbiology, 2002Co-Authors: Gui Xiang Peng, En Tao Wang, Zhi Yuan Tan, Barbara Reinhold-hurek, Wen Feng Chen, Wen Xin ChenAbstract:Eight fast-growing rhizobial isolates from Xinjiang soils were identified as Sinorhizobium xinjiangense by analyses of 16S rRNA gene sequences, SDS-PAGE of proteins, intergenic spacer sequences and DNA-DNA hybridization. Based on all of the results, these isolates and the reference strains for S. xinjiangense were a distinct genomic species, although the 16S rRNA genes were closely related to that of Sinorhizobium fredii.
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Rhizobium indigoferae sp. nov. and Sinorhizobium kummerowiae sp. nov., respectively isolated from Indigofera spp. and Kummerowia stipulacea.
International journal of systematic and evolutionary microbiology, 2002Co-Authors: Ge Hong Wei, En Tao Wang, Zhi Yuan Tan, Ming E Zhu, Wen Xin ChenAbstract:Forty-eight rhizobial isolates from root nodules of Indigofera and Kummerowia, two genera of annual or perennial wild legumes growing in the Loess Plateau in north-western China, were characterized by a polyphasic approach. Two main groups, cluster 1 and cluster 2, were defined based upon the results of numerical taxonomy, SDS-PAGE of whole-cell proteins and DNA relatedness. All the isolates within cluster 1 were isolated from Indigofera and they were identified as Rhizobium strains by 16S rRNA gene analysis. DNA relatedness of 29.5-48.9% was obtained among the cluster 1 isolates and the reference strains for defined Rhizobium species. Cluster 2 consisted of isolates from Kummerowia stipulacea and was identified as belonging to Sinorhizobium by 16S rRNA gene analyses. DNA relatedness varied from 5.2 to 41.7% among the isolates of cluster 2 and reference strains for Sinorhizobium species. Considering the existence of distinctive features among these two groups and related species within the genera Rhizobium and Sinorhizobium, we propose two novel species, Rhizobium indigoferae sp. nov. for cluster 1, with isolate CCBAU 71714(T) (= AS 1.3046(T)) as the type strain, and Sinorhizobium kummerowiae sp. nov. for cluster 2, with isolate CCBAU 71042(T) (= AS 1.3045(T)) as the type strain.
Esperanza Martínez-romero - One of the best experts on this subject based on the ideXlab platform.
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Rhizobia with different symbiotic efficiencies nodulate Acaciella angustissima in Mexico, including Sinorhizobium chiapanecum sp. nov. which has common symbiotic genes with Sinorhizobium mexicanum.
FEMS Microbiology Ecology, 2008Co-Authors: Reiner Rincón-rosales, Lourdes Lloret, Edith Ponce, Esperanza Martínez-romeroAbstract:Bacteria from nodules of the legume Acaciella angustissima native to the south of Mexico were characterized genetically and their nodulation and competitiveness were evaluated. Phylogenetic studies derived from rpoB gene sequences indicated that A. angustissima is nodulated by Sinorhizobium mexicanum, Rhizobium tropici, Mesorhizobium plurifarium and Agrobacterium tumefaciens and by bacteria related to Sinorhizobium americanum, Sinorhizobium terangae, Rhizobium etli and Rhizobium gallicum. A new lineage related to S. terangae is recognized based on the sequences of gyrA, nolR, recA, rpoB and rrs genes, DNA-DNA hybridization and phenotypic characteristics. The name for this new species is Sinorhizobium chiapanecum and its type strain is ITTG S70T. The symbiotic genes nodA and nifH were similar to those from S. mexicanum strains, which are Acaciella symbionts as well, with nodA gene sequences grouped within a cluster of nod genes from strains that nodulate plants from the Mimosoideae subfamily of the Leguminosae. Sinorhizobium isolates were the most frequently obtained from A. angustissima nodules and were among the best strains to promote plant growth in A. angustissima and to compete in interstrain nodule competition assays. Lateral transfer of symbiotic genes is not evident among the genera that nodulate A. angustissima (Rhizobium, Sinorhizobium and Mesorhizobium) but may occur among the sympatric and closely related sinorhizobia that nodulate Acaciella.
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Inactivation of the nodH gene in Sinorhizobium sp. BR816 enhances symbiosis with Phaseolus vulgaris L.
Fems Microbiology Letters, 2006Co-Authors: Roseline Remans, Esperanza Martínez-romero, Carla Snoeck, Christel Verreth, Anja Croonenborghs, Ellen Luyten, Maxime Ndayizeye, Jan Michiels, Jos VanderleydenAbstract:Sulfate modification on Rhizobium Nod factor signaling molecules is not a prerequisite for successful symbiosis with the common bean (Phaseolus vulgaris L.). However, many bean-nodulating rhizobia, including the broad host strain Sinorhizobium sp. BR816, produce sulfated Nod factors. Here, we show that the nodH gene, encoding a sulfotransferase, is responsible for the transfer of sulfate to the Nod factor backbone in Sinorhizobium sp. BR816, as was shown for other rhizobia. Interestingly, inactivation of nodH enables inoculated bean plants to fix significantly more nitrogen under different experimental setups. Our studies show that nodH in the wild-type strain is still expressed during the later stages of symbiosis. This is the first report on enhanced nitrogen fixation by blocking Nod factor sulfation.
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Sinorhizobium americanus sp. nov., a New Sinorhizobium Species Nodulating Native Acacia spp. in Mexico
Systematic and Applied Microbiology, 2004Co-Authors: Ivonne Toledo, Lourdes Lloret, Esperanza Martínez-romeroAbstract:The sinorhizobia isolated from root nodules of Acacia species native of Mexico constitute a diverse group of bacteria on the basis of their metabolic enzyme electromorphs but share restriction patterns of the PCR products of 16S rRNA genes and a common 500 kb symbiotic plasmid. They are distinguished from other Sinorhizobium species by their levels of DNA-DNA hybridization and the sequence of 16S rRNA and nifH genes. nolR gene hybridization patterns were found useful to identify sinorhizobia and characterize species. A new species, Sinorhizobium americanus, is described and the type strain is CFNEI 156 from Acacia acatlensis.
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Description of new Ensifer strains from nodules and proposal to transfer Ensifer adhaerens Casida 1982 to Sinorhizobium as Sinorhizobium adhaerens comb. nov. Request for an opinion.
International journal of systematic and evolutionary microbiology, 2003Co-Authors: Anne Willems, Esperanza Martínez-romero, Manuel Fernández-lópez, Estefania Muñoz-adelantado, Johan Goris, Paul De Vos, Nicolas Toro, Monique GillisAbstract:A group of four diverse rhizobial isolates and two soil isolates that are highly related to Ensifer adhaerens were characterized by a polyphasic approach. On the basis of DNA-DNA hybridizations and phenotypic features, these strains cannot be distinguished clearly form Ensifer adhaerens, a soil bacterium that was described in 1982, mainly on the basis of phenotypic characteristics. Phylogenetically, Ensifer and Sinorhizobium form a single group in the 16S rDNA dendrogram of the alpha-Proteobacteria, as well as in an analysis of partial recA gene sequences. They may therefore be regarded as a single genus. Because Sinorhizobium was proposed in 1988, according to the Bacteriological Code (1990 Revision) the older name, Ensifer, has priority. However, there are several reasons why a change from Sinorhizobium to Ensifer may not be the best solution and making an exception to Rule 38 may be more appropriate. We therefore propose the species Sinorhizobium adhaerens comb. nov. and put forward a Request for an Opinion to the Judicial Commission regarding the conservation of Sinorhizobium adhaerens over Ensifer adhaerens.
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Sinorhizobium morelense sp. nov., a Leucaena leucocephala-associated bacterium that is highly resistant to multiple antibiotics.
International journal of systematic and evolutionary microbiology, 2002Co-Authors: En Tao Wang, Anne Willems, Manuel Fernández-lópez, Zhi Yuan Tan, Barbara Reinhold-hurek, Esperanza Martínez-romeroAbstract:Sinorhizobium morelense sp. nov. is described to designate a group of bacteria isolated from root nodules of Leucaena leucocephala. S. morelense shows 98% 16S rRNA gene sequence similarity to some Sinorhizobium species and to Ensifer adhaerens. This novel species is distinguished from other Sinorhizobium species and from E. adhaerens by DNA-DNA hybridization, 165 rRNA gene restriction fragments and sequence and some distinctive phenotypic features. Strains of this species are highly resistant to some antibiotics, such as carbenicillin (1 mg ml(-1)), kanamycin (500 microg ml(-1)) and erythromycin (300 microg ml(-1)). They do not form nodules, but a nodulating strain, Lc57, is closely related to the novel species. Strain Lc04T (= LMG 21331T = CFN E1007T) is designated as the type strain of this novel species.
Peter Mergaert - One of the best experts on this subject based on the ideXlab platform.
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Specific Host-Responsive Associations Between Medicago truncatula Accessions and Sinorhizobium Strains
Molecular Plant-microbe Interactions, 2017Co-Authors: Théophile Kazmierczak, Marianna Nagymihály, Florian Lamouche, Quentin Barrière, Ibtissem Guefrachi, Benoit Alunni, Mouna Ouadghiri, Jamal Ibijbijen, Eva Kondorosi, Peter MergaertAbstract:Legume plants interact with rhizobia to form nitrogen-fixing root nodules. Legume-rhizobium interactions are specific and only compatible rhizobia and plant species will lead to nodule formation. Even within compatible interactions, the genotype of both the plant and the bacterial symbiont will impact on the efficiency of nodule functioning and nitrogen-fixation activity. The model legume Medicago truncatula forms nodules with several species of the Sinorhizobium genus. However, the efficiency of these bacterial strains is highly variable. In this study, we compared the symbiotic efficiency of Sinorhizobium meliloti strains Sm1021, 102F34, and FSM-MA, and Sinorhizobium medicae strain WSM419 on the two widely used M. truncatula accessions A17 and R108. The efficiency of the interactions was determined by multiple parameters. We found a high effectiveness of the FSM-MA strain with both M. truncatula accessions. In contrast, specific highly efficient interactions were obtained for the A17-WSM419 and R108-102...
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Specific Host-Responsive Associations Between Medicago truncatula Accessions and Sinorhizobium Strains
Molecular Plant-Microbe Interactions, 2017Co-Authors: Théophile Kazmierczak, Marianna Nagymihály, Florian Lamouche, Quentin Barrière, Ibtissem Guefrachi, Benoit Alunni, Mouna Ouadghiri, Jamal Ibijbijen, Eva Kondorosi, Peter MergaertAbstract:Legume plants interact with rhizobia to form nitrogen-fixing root nodules. Legume-rhizobium interactions are specific and only compatible rhizobia and plant species will lead to nodule formation. Even within compatible interactions, the genotype of both the plant and the bacterial symbiont will impact on the efficiency of nodule functioning and nitrogen-fixation activity. The model legume Medicago truncatula forms nodules with several species of the Sinorhizobium genus. However, the efficiency of these bacterial strains is highly variable. In this study, we compared the symbiotic efficiency of Sinorhizobium meliloti strains Sm1021, 102F34, and FSM-MA, and Sinorhizobium medicae strain WSM419 on the two widely used M. truncatula accessions A17 and R108. The efficiency of the interactions was determined by multiple parameters. We found a high effectiveness of the FSM-MA strain with both M. truncatula accessions. In contrast, specific highly efficient interactions were obtained for the A17-WSM419 and R108-102F34 combinations. Remarkably, the widely used Sm1021 strain performed weakly on both hosts. We showed that Sm1021 efficiently induced nodule organogenesis but cannot fully activate the differentiation of the symbiotic nodule cells, explaining its weaker performance. These results will be informative for the selection of appropriate rhizobium strains in functional studies on symbiosis using these M. truncatula accessions, particularly for research focusing on late stages of the nodulation process.
En Tao Wang - One of the best experts on this subject based on the ideXlab platform.
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Replicon-Dependent Differentiation of Symbiosis-Related Genes in Sinorhizobium Strains Nodulating Glycine max
Applied and Environmental Microbiology, 2013Co-Authors: Hui Juan Guo, En Tao Wang, Xing Xing Zhang, Yan Ming Zhang, Chang Fu Tian, Wen Xin ChenAbstract:In order to investigate the genetic differentiation of Sinorhizobium strains nodulating Glycine max and related microevolutionary mechanisms, three housekeeping genes (SMc00019, truA, and thrA) and 16 symbiosis-related genes on the chromosome (7 genes), pSymA (6 genes), and pSymB (3 genes) were analyzed. Five distinct species were identified among the test strains by calculating the average nucleotide identity (ANI) of SMc00019-truA-thrA: Sinorhizobium fredii, Sinorhizobium sojae, Sinorhizobium sp. I, Sinorhizobium sp. II, and Sinorhizobium sp. III. These species assignments were also supported by population genetics and phylogenetic analyses of housekeeping genes and symbiosis-related genes on the chromosome and pSymB. Different levels of genetic differentiation were observed among these species or different replicons. S. sojae was the most divergent from the other test species and was characterized by its low intraspecies diversity and limited geographic distribution. Intergenic recombination dominated the evolution of 19 genes from different replicons. Intraspecies recombination happened frequently in housekeeping genes and symbiosis-related genes on the chromosome and pSymB, whereas pSymA genes showed a clear pattern of lateral-transfer events between different species. Moreover, pSymA genes were characterized by a lower level of polymorphism and recombination than those on the chromosome and pSymB. Taken together, genes from different replicons of rhizobia might be involved in the establishment of symbiosis with legumes, but these symbiosis-related genes might have evolved differently according to their corresponding replicons.
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Identification of isolates from soybean nodules in Xinjiang Region as Sinorhizobium xinjiangense and genetic differentiation of S. xinjiangense from Sinorhizobium fredii.
International Journal of Systematic and Evolutionary Microbiology, 2002Co-Authors: Gui Xiang Peng, En Tao Wang, Zhi Yuan Tan, Barbara Reinhold-hurek, Wen Feng Chen, Wen Xin ChenAbstract:Eight fast-growing rhizobial isolates from Xinjiang soils were identified as Sinorhizobium xinjiangense by analyses of 16S rRNA gene sequences, SDS-PAGE of proteins, intergenic spacer sequences and DNA-DNA hybridization. Based on all of the results, these isolates and the reference strains for S. xinjiangense were a distinct genomic species, although the 16S rRNA genes were closely related to that of Sinorhizobium fredii.
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Sinorhizobium morelense sp. nov., a Leucaena leucocephala-associated bacterium that is highly resistant to multiple antibiotics.
International journal of systematic and evolutionary microbiology, 2002Co-Authors: En Tao Wang, Anne Willems, Manuel Fernández-lópez, Zhi Yuan Tan, Barbara Reinhold-hurek, Esperanza Martínez-romeroAbstract:Sinorhizobium morelense sp. nov. is described to designate a group of bacteria isolated from root nodules of Leucaena leucocephala. S. morelense shows 98% 16S rRNA gene sequence similarity to some Sinorhizobium species and to Ensifer adhaerens. This novel species is distinguished from other Sinorhizobium species and from E. adhaerens by DNA-DNA hybridization, 165 rRNA gene restriction fragments and sequence and some distinctive phenotypic features. Strains of this species are highly resistant to some antibiotics, such as carbenicillin (1 mg ml(-1)), kanamycin (500 microg ml(-1)) and erythromycin (300 microg ml(-1)). They do not form nodules, but a nodulating strain, Lc57, is closely related to the novel species. Strain Lc04T (= LMG 21331T = CFN E1007T) is designated as the type strain of this novel species.
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Rhizobium indigoferae sp. nov. and Sinorhizobium kummerowiae sp. nov., respectively isolated from Indigofera spp. and Kummerowia stipulacea.
International journal of systematic and evolutionary microbiology, 2002Co-Authors: Ge Hong Wei, En Tao Wang, Zhi Yuan Tan, Ming E Zhu, Wen Xin ChenAbstract:Forty-eight rhizobial isolates from root nodules of Indigofera and Kummerowia, two genera of annual or perennial wild legumes growing in the Loess Plateau in north-western China, were characterized by a polyphasic approach. Two main groups, cluster 1 and cluster 2, were defined based upon the results of numerical taxonomy, SDS-PAGE of whole-cell proteins and DNA relatedness. All the isolates within cluster 1 were isolated from Indigofera and they were identified as Rhizobium strains by 16S rRNA gene analysis. DNA relatedness of 29.5-48.9% was obtained among the cluster 1 isolates and the reference strains for defined Rhizobium species. Cluster 2 consisted of isolates from Kummerowia stipulacea and was identified as belonging to Sinorhizobium by 16S rRNA gene analyses. DNA relatedness varied from 5.2 to 41.7% among the isolates of cluster 2 and reference strains for Sinorhizobium species. Considering the existence of distinctive features among these two groups and related species within the genera Rhizobium and Sinorhizobium, we propose two novel species, Rhizobium indigoferae sp. nov. for cluster 1, with isolate CCBAU 71714(T) (= AS 1.3046(T)) as the type strain, and Sinorhizobium kummerowiae sp. nov. for cluster 2, with isolate CCBAU 71042(T) (= AS 1.3045(T)) as the type strain.
Philippe De Lajudie - One of the best experts on this subject based on the ideXlab platform.
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Divergent genes in potential inoculant Sinorhizobium strains are related to DNA replication, recombination, and repair.
Journal of Basic Microbiology, 2016Co-Authors: Petri Penttinen, Philippe De Lajudie, M. L. Roumiantseva, Victoria S. Muntyan, Dario Greco, Zewdu Terefework, Petri Auvinen, Kristina LindstromAbstract:To serve as inoculants of legumes, nitrogen-fixing rhizobium strains should be competitive and tolerant of diverse environments. We hybridized the genomes of symbiotically efficient and salt tolerant Sinorhizobium inoculant strains onto the Sinorhizobium meliloti Rm1021 microarray. The number of variable genes, that is, divergent or putatively multiplied genes, ranged from 503 to 1556 for S. meliloti AK23, S. meliloti STM 1064 and S. arboris HAMBI 1552. The numbers of divergent genes affiliated with the symbiosis plasmid pSymA and related to DNA replication, recombination and repair were significantly higher than expected. The variation was mainly in the accessory genome, implying that it was important in shaping the adaptability of the strains.
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Development of a lab-made microarray for analyzing the genetic diversity of nitrogen fixing symbionts Sinorhizobium meliloti and Sinorhizobium medicae.
Journal of Microbiological Methods, 2006Co-Authors: Xavier Bailly, Philippe De Lajudie, Gilles Béna, Vanina Lenief, Jean-christophe AvarreAbstract:Some bacterial species, like nitrogen-fixing Sinorhizobium that interact with Medicago plants, are prone to frequent horizontal gene transfers. Investigation of their genetic structure requires to study polymorphism patterns at many loci. Although DNA microarrays represent a method of choice for high throughput analysis of polymorphisms, this technology yet remains an expensive and heavy approach, thus depriving most of research groups from this powerful tool. In an attempt to overcome this limitation, we have developed a simple genotyping procedure by DNA microarrays, and have evaluated its ability to characterize a Sinorhizobium population. Thirty 18- to 24-mer oligonucleotide probes were designed to target the most frequent mutations in three polymorphic loci of Sinorhizobium meliloti and S. medicae. Probe hybridization efficiency was compared on two spotting surfaces: nylon membranes and epoxy-coated glass slides. Epoxy-coated glass slides revealed more sensitive than nylon membranes and allowed discrimination of single mismatches. Using this procedure, an uncharacterized population consisting of 33 S. meliloti/S. medicae isolates was successfully genotyped.
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analysis of cellular fatty acids and phenotypic relationships of agrobacterium bradyrhizobium mesorhizobium rhizobium and Sinorhizobium species using the sherlock microbial identification system
International Journal of Systematic and Evolutionary Microbiology, 2000Co-Authors: S W Tighe, K Dipietro, Giselle Nick, Philippe De Lajudie, Kristina Lindstrom, B. D. W. JarvisAbstract:Previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. In this study, the fatty acid profiles of over 600 strains belonging to the genera Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium were evaluated using the gaschromatography-based Sherlock Microbial Identification System (MIS). Data collected with the MIS showed that the three phylogenetically defined biovars of the genus Agrobacterium formed discrete clusters, whilst species belonging to the genus Mesorhizobium formed three subclusters which were easily distinguished. These three subclusters contained Mesorhizobium ciceri and Mesorhizobium mediterraneum, Mesorhizobium tianshanense fatty acid group I and Mesorhizobium plurifarium, and Mesorhizobium huakuii and Mesorhizobium loti. The genus Sinorhizobium was composed of an individual position for Sinorhizobium meliloti and a large cluster comprising Sinorhizobium fredii, Sinorhizobium saheli, Sinorhizobium terangae, Sinorhizobium kostiense and Sinorhizobium arboris. S. meliloti contained significantly higher levels of the fatty acid 19:0 cyclo omega 8 cis and clustered with Rhizobium sp. (Hedysarum coronarium). However, discrimination between the species of genera Sinorhizobium and Rhizobium was a function of the concentration of 16:0 3-OH. The genus Rhizobium contained a single cluster containing Rhizobium sp. (Hedysarum coronarium), Rhizobium gallicum, Rhizobium leguminosarum and Rhizobium etli, along with individual positions for Rhizobium giardinii, Rhizobium tropici, Rhizobium galegae and Rhizobium hainanense. R. tropici and R. hainanense exhibited similarity to Agrobacterium biovar 2, whilst R. galegae was similar to Agrobacterium biovar 1. R. giardinii appeared unique, with comparatively little similarity to the other species. Analysis of the genus Bradyrhizobium revealed large differences from the other genera studied. Two subgroups of Bradyrhizobium elkanii were detected and easily distinguished from Bradyrhizobium japonicum. Bradyrhizobium liaoningense and Bradyrhizobium sp. (Arachis hypogaea), a group isolated from Chinese peanut plants, showed similarities to B. japonicum, whilst a subgroup of M. tianshanense appeared identical to Bradyrhizobium sp. (Arachis hypogaea).
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Sinorhizobium arboris sp. nov. and Sinorhizobium kostiense sp. nov., isolated from leguminous trees in Sudan and Kenya.
International journal of systematic bacteriology, 1999Co-Authors: G Nick, Philippe De Lajudie, B D Eardly, S Suomalainen, L Paulin, X Zhang, M Gillis, K LindströmAbstract:SDS-PAGE of total bacterial proteins was applied to the classification of 25 Sudanese and five Kenyan strains isolated from the root nodules of Acacia senegal and Prosopis chilensis. Twenty strains were also studied by multilocus enzyme electrophoresis (MLEE) and the whole 16S rRNA gene was sequenced from two strains representing the two major clusters. These results, together with the previously reported numerical taxonomy analysis, pulsed-field gel electrophoresis studies, DNA-DNA dot-blot hybridization, genomic fingerprinting using repetitive sequence-based PCR, DNA base composition analysis, DNA-DNA reassociation analysis, partial sequencing of the 16S rRNA gene and RFLP analysis of the amplified 16S rRNA gene, showed that all 30 strains belong to the genus Sinorhizobium. Two of the strains grouped with Sinorhizobium saheli and seven with Sinorhizobium terangae, while the rest did not cluster with any of the established species. The majority of the strains formed two phenotypically and genotypically distinct groups and we therefore propose that these strains should be classified as two new species, Sinorhizobium arboris sp. nov. and Sinorhizobium kostiense sp. nov.
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the sesbania root symbionts Sinorhizobium saheli and s teranga bv sesbaniae can form stem nodules on sesbania rostrata although they are less adapted to stem nodulation than azorhizobium caulinodans
Applied and Environmental Microbiology, 1997Co-Authors: Caroline Boivin, Ibrahima Ndoye, Gilles Lortet, Philippe De Lajudie, A. Ndiaye, Bernard DreyfusAbstract:Sesbania species can establish symbiotic interactions with rhizobia from two taxonomically distant genera, including the Sesbania rostrata stem-nodulating Azorhizobium sp. and Azorhizobium caulinodans and the newly described Sinorhizobium saheli and Sinorhizobium teranga bv. sesbaniae, isolated from the roots of various Sesbania species. A collection of strains from both groups were analyzed for their symbiotic properties with different Sesbania species. S. saheli and S. teranga bv. sesbaniae strains were found to effectively stem nodulate Sesbania rostrata, showing that stem nodulation is not restricted to Azorhizobium. Sinorhizobia and azorhizobia, however, exhibited clear differences in other aspects of symbiosis. Unlike Azorhizobium, S. teranga bv. sesbaniae and S. saheli did not induce effective stem nodules on plants previously inoculated on the roots, although stem nodulation was arrested at different stages. For Sesbania rostrata root nodulation, Sinorhizobium appeared more sensitive than Azorhizobium to the presence of combined nitrogen. S. saheli and S. teranga bv. sesbaniae were effective symbionts with all Sesbania species tested, while Azorhizobium strains fixed nitrogen only in symbiosis with Sesbania rostrata. In a simple screening test, S. saheli and S. teranga bv. sesbaniae were incapable of asymbiotic nitrogenase activity. Thus, Azorhizobium can easily be distinguished from Sinorhizobium among Sesbania symbionts on the basis of symbiotic and free-living nitrogen fixation. The ability of Azorhizobium to overcome the systemic plant control appears to be a stem adaptation function. This last property, together with its host-specific symbiotic nitrogen fixation, makes Azorhizobium highly specialized for stem nodulation of the aquatic legume Sesbania rostrata.
