Artykuły w czasopismach: „Rhizobium loti”

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Jarvis, B. D. W., P. Van Berkum, W. X. Chen, S. M. Nour, M. P. Fernandez, J. C. Cleyet-Marel i M. Gillis. "Transfer of Rhizobium loti, Rhizobium huakuii, Rhizobium ciceri, Rhizobium mediterraneum, and Rhizobium tianshanense to Mesorhizobium gen. nov." International Journal of Systematic and Evolutionary Microbiology 47, nr 3 (1.07.1997): 895–98. http://dx.doi.org/10.1099/00207713-47-3-895.

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Boncompagni, Eric, Magne Østerås, Marie-Christine Poggi i Daniel le Rudulier. "Occurrence of Choline and Glycine Betaine Uptake and Metabolism in the Family Rhizobiaceae and Their Roles in Osmoprotection". Applied and Environmental Microbiology 65, nr 5 (1.05.1999): 2072–77. http://dx.doi.org/10.1128/aem.65.5.2072-2077.1999.

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ABSTRACT The role of glycine betaine and choline in osmoprotection of various Rhizobium, Sinorhizobium,Mesorhizobium, Agrobacterium, andBradyrhizobium reference strains which display a large variation in salt tolerance was investigated. When externally provided, both compounds enhanced the growth of Rhizobium tropici,Sinorhizobium meliloti, Sinorhizobium fredii,Rhizobium galegae, Agrobacterium tumefaciens,Mesorhizobium loti, and Mesorhizobium huakuii, demonstrating their utilization as osmoprotectants. However, both compounds were inefficient for the most salt-sensitive strains, such asRhizobium leguminosarum (all biovars), Agrobacterium rhizogenes, Rhizobium etli, and Bradyrhizobium japonicum. Except for B. japonicum, all strains exhibit transport activity for glycine betaine and choline. When the medium osmolarity was raised, choline uptake activity was inhibited, whereas glycine betaine uptake was either increased in R. leguminosarum and S. meliloti or, more surprisingly, reduced in R. tropici, S. fredii, and M. loti. The transport of glycine betaine was increased by growing the cells in the presence of the substrate. With the exception ofB. japonicum, all strains were able to use glycine betaine and choline as sole carbon and nitrogen sources. This catabolic function, reported for only a few soil bacteria, could increase competitiveness of rhizobial species in the rhizosphere. Choline dehydrogenase and betaine-aldehyde dehydrogenase activities were present in the cells of all strains with the exception of M. huakuii and B. japonicum. The main physiological role of glycine betaine in the family Rhizobiaceae seems to be as an energy source, while its contribution to osmoprotection is restricted to certain strains.

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Estrella, Marï¿½a Julia, Socorro Muï¿½oz, Marï¿½a Josï¿½ Soto, Oscar Ruiz i Juan Sanjuï¿½n. "Genetic Diversity and Host Range of Rhizobia Nodulating Lotus tenuis in Typical Soils of the Salado River Basin (Argentina)". Applied and Environmental Microbiology 75, nr 4 (12.12.2008): 1088–98. http://dx.doi.org/10.1128/aem.02405-08.

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ABSTRACT A total of 103 root nodule isolates were used to estimate the diversity of bacteria nodulating Lotus tenuis in typical soils of the Salado River Basin. A high level of genetic diversity was revealed by repetitive extragenic palindromic PCR, and 77 isolates with unique genomic fingerprints were further differentiated into two clusters, clusters A and B, after 16S rRNA restriction fragment length polymorphism analysis. Cluster A strains appeared to be related to the genus Mesorhizobium, whereas cluster B was related to the genus Rhizobium. 16S rRNA sequence and phylogenetic analysis further supported the distribution of most of the symbiotic isolates in either Rhizobium or Mesorhizobium: the only exception was isolate BA135, whose 16S rRNA gene was closely related to the 16S rRNA gene of the genus Aminobacter. Most Mesorhizobium-like isolates were closely related to Mesorhizobium amorphae, Mesorhizobium mediterraneum, Mesorhizobium tianshanense, or the broad-host-range strain NZP2037, but surprisingly few isolates grouped with Mesorhizobium loti type strain NZP2213. Rhizobium-like strains were related to Rhizobium gallicum, Rhizobium etli, or Rhizobium tropici, for which Phaseolus vulgaris is a common host. However, no nodC or nifH genes could be amplified from the L. tenuis isolates, suggesting that they have rather divergent symbiosis genes. In contrast, nodC genes from the Mesorhizobium and Aminobacter strains were closely related to nodC genes from narrow-host-range M. loti strains. Likewise, nifH gene sequences were very highly conserved among the Argentinian isolates and reference Lotus rhizobia. The high levels of conservation of the nodC and nifH genes suggest that there was a common origin of the symbiosis genes in narrow-host-range Lotus symbionts, supporting the hypothesis that both intrageneric horizontal gene transfer and intergeneric horizontal gene transfer are important mechanisms for the spread of symbiotic capacity in the Salado River Basin.

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Pankhurst, Clive E., Douglas H. Hopcroft i William T. Jones. "Comparative morphology and flavolan content of Rhizobium loti induced effective and ineffective root nodules on Lotus species, Leuceana leucocephala, Carmichaelia flagelliformis, Ornithopus sativus, and Clianthus puniceus". Canadian Journal of Botany 65, nr 12 (1.12.1987): 2676–85. http://dx.doi.org/10.1139/b87-358.

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The morphology of Rhizobium loti induced root nodules and the flavolan content of nodulated roots of several Lotus species, Leuceana leucocephala, Carmichaelia flagelliformis, Ornithopus sativus, and Clianthus puniceus were examined. Rhizobium loti strain NZP2037 formed effective (Nod+Fix+) nodules on all legumes, but strain NZP2213 formed Nod+Fix+ nodules only on Lotus corniculatus var. cree and ineffective (Nod+Fix−) nodules on all other legumes. The Nod+Fix− nodules developed by NZP2213 showed morphologies ranging from the complete absence of bacteria within “tumour-like” structures to the development of nodules containing bacteria that were either not released or only incompletely released from infection threads. Within nodules formed by NZP2213 on Lotus corniculatus var. hirsutus and Carmichaelia flagelliformis the rhizobia had multiplied extensively within unwalled, plasma membrane bound, infection droplets. Flavolans rich in prodelphinidin, which is toxic towards NZP2213, were present in the roots of Lotus angustissimus, Lotus pedunculatus, Lotus subbiflorus, and Leuceana leucocephala, but only trace amounts of flavolan were found in the roots of Carmichaelia flagelliformis, Ornithopus sativus, and Clianthus puniceus.

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Gault, RR, A. Pilka, DM Hebb i J. Brockwell. "Nodulation studies on legumes exotic to Australia: symbiotic relationships between Chamaecytisus palmensis (tagasaste) and Lotus spp". Australian Journal of Experimental Agriculture 34, nr 3 (1994): 385. http://dx.doi.org/10.1071/ea9940385.

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Strains of rhizobia were isolated from soil around the roots of tagasaste (Chamaecytisus palmensis) growing at 15 widely separated locations in south-eastem Australia. A further collection of strains of both Rhizobium loti and Bradyrhizobium sp. (Lotus) was assembled from 18 legumes including Lotus and other species symbiotically related to Lotus. The strains were used to inoculate tagasaste and 4 species of Lotus in experiments conducted under bacteriologically controlled conditions in a temperature-controlled glasshouse. Tagasaste formed nodules and fixed N2 with all of its homologous rhizobia but there was a wide range of effectiveness among the 15 strains. Tagasaste also formed nodules with each of the 18 strains from other species but fixed N2 with only 10. Four species of Lotus were inoculated with 3 tagasaste strains. One strain nodulated each species and fixed N2 with L. conimhricensis and L. corniculatus but not with L. parviflorus or L. pedunculatus. A second tagasaste strain formed nodules with all 4 Lotus spp. but did not fix N2, while the third nodulated only L. pedunculatus but did not fix N2. A pattern analysis based on the nodulating ability of the host plants in association with 21 strains showed that tagasaste and L. corniculatus formed 1 symbiotic group, and the other 3 Lotus species formed a third group. The pattern analysis procedure based on nodulating capacity of 21 rhizobial strains in association with the 5 host species indicated substantial symbiotic diversity within the collection, with the strains comprising 8 different symbiotic groups. No strain was highly effective on both tagasaste and any of the 4 species of Lotus. Data were insufficient to classify the root-nodule bacteria of tagasaste as either Rhizobium loti or Bradyrhizobium sp. (Lotus).

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Elkan, G. H. "Taxonomy of the rhizobia". Canadian Journal of Microbiology 38, nr 6 (1.06.1992): 446–50. http://dx.doi.org/10.1139/m92-075.

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Extensive cross testing on a relatively few legume hosts led initially to a taxonomic characterization of rhizobia based on bacteria–plant cross–inoculation groups. This has gradually become less acceptable, and has been replaced by taxonomic groupings derived from numerical taxonomy, carbohydrate metabolism, antibiotic susceptiblities, serology, and various molecular techniques. It has long been recognized that there are two distinct groups of rhizobia based on growth rate. The fast-growing genus Rhizobium includes R. leguminosarum, R. meliloti, R. loti, R. galegae, R. tropici, and R. huakuii. The slow-growing genus Bradyrhizobium contains only one recognized species, B. japonicum. Two new genera have been recognized: Azorhizobium, with one recognized species (A. caulinadans), and Sinorhizobium, with two species (S. fredii and S. xinjiangensis). Genetic studies of both the fast- and slow-growing groups show unacceptably wide intrageneric and intergeneric diversity. Although there have been some elegant studies of some of the genetic relationships among rhizobia, overall there has (have) not been the comprehensive study(ies) needed to allow a conclusive taxonomic scheme. Because proposals for revision are accelerating, minimum standards have been proposed by the International Subcommittee for the Taxonomy of Rhizobium and Agrobacterium. Key words: Rhizobium taxonomy, classification of rhizobia, interrelationships of rhizobia.

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López-Lara, Isabel M., Dimitris Kafetzopoulos, Herman P. Spaink i Jane E. Thomas-Oates. "Rhizobial NodL O-Acetyl Transferase and NodS N-Methyl Transferase Functionally Interfere in Production of Modified Nod Factors". Journal of Bacteriology 183, nr 11 (1.06.2001): 3408–16. http://dx.doi.org/10.1128/jb.183.11.3408-3416.2001.

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ABSTRACT The products of the rhizobial nodulation genes are involved in the biosynthesis of lipochitin oligosaccharides (LCOs), which are host-specific signal molecules required for nodule formation. The presence of an O-acetyl group on C-6 of the nonreducingN-acetylglucosamine residue of LCOs is due to the enzymatic activity of NodL. Here we show that transfer of the nodLgene into four rhizobial species that all normally produce LCOs that are not modified on C-6 of the nonreducing terminal residue results in production of LCOs, the majority of which have an acetyl residue substituted on C-6. Surprisingly, in transconjugant strains ofMesorhizobium loti, Rhizobium etli, and Rhizobium tropici carrying nodL, such acetylation of LCOs prevents the endogenous nodS-dependent transfer of theN-methyl group that is found as a substituent of the acylated nitrogen atom. To study this interference betweennodL and nodS, we have cloned thenodS gene of M. loti and used its product in in vitro experiments in combination with purified NodL protein. It has previously been shown that a chitooligosaccharide N deacetylated on the nonreducing terminus (the so-called NodBC metabolite) is the preferred substrate for NodS as well as for NodL. Here we show that the NodBC metabolite, acetylated by NodL, is not used by the NodS protein as a substrate while the NodL protein can acetylate the NodBC metabolite that has been methylated by NodS.

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Sivakumaran, S., B. D. W. Jarvis i P. J. Lockhart. "Identification of soil bacteria expressing a symbiotic plasmid from Rhizobium leguminosarum bv. trofolii". Canadian Journal of Microbiology 43, nr 2 (1.02.1997): 164–77. http://dx.doi.org/10.1139/m97-022.

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A hundred strains of non-nodulating, Gram-negative, rod-shaped bacteria were isolated from clover–ryegrass pastures on three different soil types and from a sandy loam under lupins. When crossed with Escherichia coli PN200 containing the cointegrate plasmid pPN1, 11 transconjugants gained the ability to form nodules on the roots of white clover (Trifolium repens cv. Grasslands Huia). A nodA probe indicated that they had gained nodulation genes. The identities of these 11 strains and 4 others derived from earlier work on non-nodulating root nodule bacteria, were determined by ribotyping, DNA – DNA hybridization, and partial 16S rRNA sequencing. Good agreement was obtained between the three methods, and 11 of the strains were identified as Rhizobium leguminosarum (6), Rhizobium loti (2), Rhizobium etli (1), Rhizobium tropici (1), and Sinorhizobium meliloti (1). DNA –DNA hybridization indicated that the remaining four strains were related to the Rhizobium leguminosarum reference strains. The existence of several species of non-nodulating rhizobia in pasture soil, including species for which the normal host plant was absent, is discussed in relation to the fate of symbiotic plasmids from Rhizobium seed inoculants. It is also suggested that new species should be named for the geographical region from which they are first isolated rather than the host plant.Key words: Rhizobium, non-nodulating, nonsymbiotic, isolation, identification.

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Banba, Mari, Abu-Baker M. Siddique, Hiroshi Kouchi, Katsura Izui i Shingo Hata. "Lotus japonicus Forms Early Senescent Root Nodules with Rhizobium etli". Molecular Plant-Microbe Interactions® 14, nr 2 (luty 2001): 173–80. http://dx.doi.org/10.1094/mpmi.2001.14.2.173.

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Mesorhizobium loti and Rhizobium etli are microsymbionts of the Lotus and Phaseolus spp., respectively, and secrete essentially the same Nod factors. Lotus japonicus efficiently formed root nodules with R. etli CE3, irrespective of the presence or absence of a flavonoid-independent transcription activator nodD gene. On a nitrogen-free medium, however, the host plant inoculated with R. etli showed a severe nitrogen deficiency symptom. Initially, the nodules formed with R. etli were pale pink and leghemoglobin mRNA was detectable at significant levels. Nevertheless, the nodules became greenish with time. Acetylene-reduction activity of nodules formed with R. etli was comparable with that formed by M. loti 3 weeks postinoculation, but thereafter it decreased rapidly. The nodules formed with R. etli contained much more starch granules than those formed with M. loti. R. etli developed into bacteroids in the L. japonicus nodules, although the density of bacteroids in the infected cells was lower than that in the nodules formed with M. loti. The nodules formed with R. etli were of the early senescence type, in that membrane structures were drastically disintegrated in the infected cells of the greenish nodules. Thus, L. japonicus started and then ceased a symbiotic relationship with R. etli at the final stage.

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Yang, Menghua, Kejing Sun, Lei Zhou, Ruifu Yang, Zengtao Zhong i Jun Zhu. "Functional analysis of three AHL autoinducer synthase genes in Mesorhizobium loti reveals the important role of quorum sensing in symbiotic nodulation". Canadian Journal of Microbiology 55, nr 2 (luty 2009): 210–14. http://dx.doi.org/10.1139/w08-128.

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One of the most important signal transduction pathways in bacteria, quorum sensing, is involved in many regulatory circuits in rhizobia, especially in the control of communication between rhizobia and their plant hosts. In this study, we identified 3 autoinducer synthase genes — mrlI1, mrlI2, and mrlI3 — in Mesorhizobium loti NZP 2213. We found that MrlI1 and MrlI2 could synthesize distinct N-acyl homoserine lactone (AHL) autoinducers in rich medium cultures, and the expression of mrlI1 was shown to be growth-phase-dependent. MrlI3 did not produce any detectable AHL molecules under the culture conditions tested. To investigate whether these AHL synthases affect nodulation, we examined the nodulation of AHL-deficient mutants on their native plant host Lotus corniculatus and found that the efficiency of nodulation of bacteria with mutations of any of these 3 synthase genes was reduced, suggesting that quorum sensing systems in M. loti may play an important role in successful establishment of rhizobium–legume symbiosis.

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Ke, Danxia, i Kunpeng Peng. "The expression of LjROP4 is required for rhizobial infection in Lotus japonicus". Canadian Journal of Plant Science 99, nr 6 (1.12.2019): 897–904. http://dx.doi.org/10.1139/cjps-2019-0056.

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Increasing evidence suggests that Rho of plant (ROP) GTPases play important roles in the rhizobium–legume symbiotic nodulation, but the molecular mechanisms of their regulation in symbiosis remain poorly understood. In this study, we showed that ROP4 in Lotus japonicus (LjROP4) is involved in the symbiotic interaction between L. japonicus and Mesorhizobium loti. Tissue expression analysis showed that LjROP4 expressed highly in the root. Histochemical staining analysis showed that after rhizobia inoculation, GUS reporter activity increased in the root vascular bundle, root tip, and lateral root primordia. During nodule development, GUS activity was detected in the cortex of nodule primordia and young nodules. In the mature nodules, GUS activity was detected only in the vascular bundle. Compared with the control, the overexpression of ROP4 and ROP4-CA produced much more pronounced root hair swelling and curling induced by M. loti. The infection event and nodule number noticeably increased, which was consistent with this promotion of root hair deformation. Moreover, RNA interference of LjROP4 produced opposite phenotypes. These data suggest that LjROP4 is required for root hair deformation during rhizobial infection. Thus, our study provides important information about root hair deformation responses induced by nod factors in the early stages of symbiotic interaction.

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Safronova, Vera I., Polina V. Guro, Anna L. Sazanova, Irina G. Kuznetsova, Andrey A. Belimov, Valentin V. Yakubov, Elizaveta R. Chirak i in. "Rhizobial Microsymbionts of Kamchatka Oxytropis Species Possess Genes of the Type III and VI Secretion Systems, Which Can Affect the Development of Symbiosis". Molecular Plant-Microbe Interactions® 33, nr 10 (październik 2020): 1232–41. http://dx.doi.org/10.1094/mpmi-05-20-0114-r.

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A collection of rhizobial strains isolated from root nodules of the narrowly endemic legume species Oxytropis erecta, O. anadyrensis, O. kamtschatica, and O. pumilio originating from the Kamchatka Peninsula (Russian Federation) was obtained. Analysis of the 16S ribosomal RNA gene sequence showed a significant diversity of isolates belonging to families Rhizobiaceae (genus Rhizobium), Phyllobacteriaceae (genera Mesorhizobium, Phyllobacterium), and Bradyrhizobiaceae (genera Bosea, Tardiphaga). A plant nodulation assay showed that only strains belonging to genus Mesorhizobium could form nitrogen-fixing nodules on Oxytropis plants. The strains M. loti 582 and M. huakuii 583, in addition to symbiotic clusters, possessed genes of the type III and type VI secretion systems (T3SS and T6SS, respectively), which can influence the host specificity of strains. These strains formed nodules of two types (elongated and rounded) on O. kamtschatica roots. We suggest this phenomenon may result from Nod factor–dependent and –independent nodulation strategies. The obtained strains are of interest for further study of the T3SS and T6SS gene function and their role in the development of rhizobium-legume symbiosis. The prospects of using rhizobia having both gene systems related to symbiotic and nonsymbiotic nodulation strategies to enhance the efficiency of plant-microbe interactions by expanding the host specificity and increasing nodulation efficiency are discussed.

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Lepek, Viviana, Yolanda Navarro de Navarro i Rodolfo A. Ugalde. "Synthesis of β(1–2)glucan in Rhizobium loti". Archives of Microbiology 155, nr 1 (grudzień 1990): 35–41. http://dx.doi.org/10.1007/bf00291271.

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Chen, Yaping, Fengjiao Li, Lu Tian, Mingchao Huang, Rufang Deng, Xueliu Li, Wei Chen i in. "The Phenylalanine Ammonia Lyase Gene LjPAL1 Is Involved in Plant Defense Responses to Pathogens and Plays Diverse Roles in Lotus japonicus-Rhizobium Symbioses". Molecular Plant-Microbe Interactions® 30, nr 9 (wrzesień 2017): 739–53. http://dx.doi.org/10.1094/mpmi-04-17-0080-r.

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Phenylalanine ammonia lyase (PAL) is important in the biosynthesis of plant secondary metabolites that regulate growth responses. Although its function is well-established in various plants, the functional significance of PAL genes in nodulation is poorly understood. Here, we demonstrate that the Lotus japonicus PAL (LjPAL1) gene is induced by Mesorhizobium loti infection and methyl-jasmonate (Me-JA) treatment in roots. LjPAL1 altered PAL activity, leading to changes in lignin contents and thicknesses of cell walls in roots and nodules of transgenic plants and, hence, to structural changes in roots and nodules. LjPAL1-knockdown plants (LjPAL1i) exhibited increased infection thread and nodule numbers and the induced upregulation of nodulin gene expression after M. loti infection. Conversely, LjPAL1 overexpression delayed the infection process and reduced infection thread and nodule numbers after M. loti inoculation. LjPAL1i plants also exhibited reduced endogenous salicylic acid (SA) accumulation and expression of the SA-dependent marker gene. Their infection phenotype could be partially restored by exogenous SA or Me-JA application. Our data demonstrate that LjPAL1 plays diverse roles in L. japonicus–rhizobium symbiosis, affecting rhizobial infection progress and nodule structure, likely by inducing lignin modification, regulating endogenous SA biosynthesis, and modulating SA signaling.

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Brito, Belén, Jorge Monza, Juan Imperial, Tomás Ruiz-Argüeso i Jose Manuel Palacios. "Nickel Availability and hupSL Activation by Heterologous Regulators Limit Symbiotic Expression of theRhizobium leguminosarum bv. Viciae Hydrogenase System in Hup− Rhizobia". Applied and Environmental Microbiology 66, nr 3 (1.03.2000): 937–42. http://dx.doi.org/10.1128/aem.66.3.937-942.2000.

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ABSTRACT A limited number of Rhizobium andBradyrhizobium strains possess a hydrogen uptake (Hup) system that recycles the hydrogen released from the nitrogen fixation process in legume nodules. To extend this ability to rhizobia that nodulate agronomically important crops, we investigated factors that affect the expression of a cosmid-borne Hup system from Rhizobium leguminosarum bv. viciae UPM791 in R. leguminosarumbv. viciae, Rhizobium etli, Mesorhizobium loti, and Sinorhizobium meliloti Hup− strains. After cosmid pAL618 carrying the entire hup system of strain UPM791 was introduced, all recipient strains acquired the ability to oxidize H2 in symbioses with their hosts, although the levels of hydrogenase activity were found to be strain and species dependent. The levels of hydrogenase activity were correlated with the levels of nickel-dependent processing of the hydrogenase structural polypeptides and with transcription of structural genes. Expression of the NifA-dependent hupSL promoter varied depending on the genetic background, while the hyp operon, which is controlled by the FnrN transcriptional regulator, was expressed at similar levels in all recipient strains. With the exception of theR. etli-bean symbiosis, the availability of nickel to bacteroids strongly affected hydrogenase processing and activity in the systems tested. Our results indicate that efficient transcriptional activation by heterologous regulators and processing of the hydrogenase as a function of the availability of nickel to the bacteroid are relevant factors that affect hydrogenase expression in heterologous rhizobia.

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Baraibar, Amalia, Llillian Frioni, Maria Elena Guedes i Hans Ljunggren. "Symbiotic effectiveness and ecological characterization of indigenous Rhizobium loti populations in Uruguay". Pesquisa Agropecuária Brasileira 34, nr 6 (czerwiec 1999): 1010–17. http://dx.doi.org/10.1590/s0100-204x1999000600012.

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The objectives of this work were to describe the distribution, density and seasonal variation of the indigenous populations of Rhizobium loti in different Uruguayan soils and to determine the symbiotic effectiveness and stress tolerance factors of different isolates, both with the aim of obtaining selected strains to re-introduce as inoculants in Lotus pastures. R. loti was present in ten soils studied and their densities varied from year to year and within each soil. All the isolates nodulated Lotus corniculatus effectively. The nodules in Lotus pedunculatus and Lotus subbiflorus were small, red on the surface and ineffective in nitrogen fixation. The study of 50 isolates from the ten soils showed high variability in their symbiotic efficiency and tolerance to pH. The indigenous population was acid tolerant in culture medium (pH 4.5), 83% of them could grow at pH 4.5 in 3 days. This work showed that there was a great diversity between the strains of R. loti isolated from Uruguayan soils and supports the importance of selecting among them the most efficient and resistant strains to be included in the inoculants.

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Bjourson, A. J., i J. E. Cooper. "Isolation of Rhizobium loti Strain-Specific DNA Sequences by Subtraction Hybridization". Applied and Environmental Microbiology 54, nr 11 (1988): 2852–55. http://dx.doi.org/10.1128/aem.54.11.2852-2855.1988.

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Russa, Ryszard, Teresa Urbanik-Sypniewska, Kristina Lindstr�m i Hubert Mayer. "Chemical characterization of two lipopolysaccharide species isolated from Rhizobium loti NZP2213". Archives of Microbiology 163, nr 5 (maj 1995): 345–51. http://dx.doi.org/10.1007/bf00404207.

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Russa, Ryszard, Teresa Urbanik-Sypniewska, Kristina Lindstr�m i H. Mayer. "Chemical characterization of two lipopolysaccharide species isolated from Rhizobium loti NZP2213". Archives of Microbiology 163, nr 5 (1.05.1995): 345–51. http://dx.doi.org/10.1007/s002030050213.

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Broughton, W. J., C. H. Wong, A. Lewin, U. Samrey, H. Myint, H. Meyer, D. N. Dowling i R. Simon. "Identification of Rhizobium plasmid sequences involved in recognition of Psophocarpus, Vigna, and other legumes." Journal of Cell Biology 102, nr 4 (1.04.1986): 1173–82. http://dx.doi.org/10.1083/jcb.102.4.1173.

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Symbiotic DNA sequences involved in nodulation by Rhizobium must include genes responsible for recognizing homologous hosts. We sought these genes by mobilizing the symbiotic plasmid of a broad host-range Rhizobium MPIK3030 (= NGR234) that can nodulate Glycine max, Psophocarpus tetragonolobus, Vigna unguiculata, etc., into two Nod- Rhizobium mutants as well as into Agrobacterium tumefaciens. Subsequently, cosmid clones of pMPIK3030a were mobilized into Nod+ Rhizobium that cannot nodulate the chosen hosts. Nodule development was monitored by examining the ultrastructure of nodules formed by the transconjugants. pMPIK3030a could complement Nod- and Nif- deletions in R. leguminosarum and R. meliloti as well as enable A. tumefaciens to nodulate. Three non-overlapping sets of cosmids were found that conferred upon a slow-growing Rhizobium species, as well as on R. loti and R. meliloti, the ability to nodulate Psophocarpus and Vigna, thus pointing to the existence of three sets of host-specificity genes. Recipients harboring these hsn regions had truly broadened host-range since they could nodulate both their original hosts as well as MPIK3030 hosts.

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Eardly, B. D., S. M. Nour, P. van Berkum i R. K. Selander. "Rhizobial 16S rRNA and dnaK Genes: Mosaicism and the Uncertain Phylogenetic Placement of Rhizobium galegae". Applied and Environmental Microbiology 71, nr 3 (marzec 2005): 1328–35. http://dx.doi.org/10.1128/aem.71.3.1328-1335.2005.

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ABSTRACT The phylogenetic relatedness among 12 agriculturally important species in the order Rhizobiales was estimated by comparative 16S rRNA and dnaK sequence analyses. Two groups of related species were identified by neighbor-joining and maximum-parsimony analysis. One group consisted of Mesorhizobium loti and Mesorhizobium ciceri, and the other group consisted of Agrobacterium rhizogenes, Rhizobium tropici, Rhizobium etli, and Rhizobium leguminosarum. Although bootstrap support for the placement of the remaining six species varied, A. tumefaciens, Agrobacterium rubi, and Agrobacterium vitis were consistently associated in the same subcluster. The three other species included Rhizobium galegae, Sinorhizobium meliloti, and Brucella ovis. Among these, the placement of R. galegae was the least consistent, in that it was placed flanking the A. rhizogenes-Rhizobium cluster in the dnaK nucleotide sequence trees, while it was placed with the other three Agrobacterium species in the 16S rRNA and the DnaK amino acid trees. In an effort to explain the inconsistent placement of R. galegae, we examined polymorphic site distribution patterns among the various species. Localized runs of nucleotide sequence similarity were evident between R. galegae and certain other species, suggesting that the R. galegae genes are chimeric. These results provide a tenable explanation for the weak statistical support often associated with the phylogenetic placement of R. galegae, and they also illustrate a potential pitfall in the use of partial sequences for species identification.

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Nagata, Maki, Ei-ichi Murakami, Yoshikazu Shimoda, Fuyuko Shimoda-Sasakura, Ken-ichi Kucho, Akihiro Suzuki, Mikiko Abe, Shiro Higashi i Toshiki Uchiumi. "Expression of a Class 1 Hemoglobin Gene and Production of Nitric Oxide in Response to Symbiotic and Pathogenic Bacteria in Lotus japonicus". Molecular Plant-Microbe Interactions® 21, nr 9 (wrzesień 2008): 1175–83. http://dx.doi.org/10.1094/mpmi-21-9-1175.

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Symbiotic nitrogen fixation by the collaboration between leguminous plants and rhizobia is an important system in the global nitrogen cycle, and some molecular aspects during the early stage of host-symbiont recognition have been revealed. To understand the responses of a host plant against various bacteria, we examined expression of hemoglobin (Hb) genes and production of nitric oxide (NO) in Lotus japonicus after inoculation with rhizobia or plant pathogens. When the symbiotic rhizobium Mesorhizobium loti was inoculated, expression of LjHb1 and NO production were induced transiently in the roots at 4 h after inoculation. In contrast, inoculation with the nonsymbiotic rhizobia Sinorhizobium meliloti and Bradyrhizobium japonicum induced neither expression of LjHb1 nor NO production. When L. japonicus was inoculated with plant pathogens (Ralstonia solanacearum or Pseudomonas syringae), continuous NO production was observed in roots but induction of LjHb1 did not occur. These results suggest that modulation of NO levels and expression of class 1 Hb are involved in the establishment of the symbiosis.

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López-Lara, Isabel M., Jorrit D. J. Berg, Jane E. Thomas-Oates, John Glushka, Ben J. J. Lugtenberg i Herman P. Spaink. "Structural identification of the iipo-chitin oligosaccharide nodulation signals of Rhizobium loti". Molecular Microbiology 15, nr 4 (27.10.2006): 627–38. http://dx.doi.org/10.1111/j.1365-2958.1995.tb02372.x.

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Scott, D. B., R. Wilson, G. J. Shaw, A. Petit i J. Tempe. "Biosynthesis and degradation of nodule-specific Rhizobium loti compounds in Lotus nodules." Journal of Bacteriology 169, nr 1 (1987): 278–82. http://dx.doi.org/10.1128/jb.169.1.278-282.1987.

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Chua, K. Y., C. E. Pankhurst, P. E. Macdonald, D. H. Hopcroft, B. D. Jarvis i D. B. Scott. "Isolation and characterization of transposon Tn5-induced symbiotic mutants of Rhizobium loti." Journal of Bacteriology 162, nr 1 (1985): 335–43. http://dx.doi.org/10.1128/jb.162.1.335-343.1985.

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Estrella, M. J., F. L. Pieckenstain, M. Marina, L. E. D�az i O. A. Ruiz. "Cheese whey: an alternative growth and protective medium for Rhizobium loti cells". Journal of Industrial Microbiology and Biotechnology 31, nr 3 (1.03.2004): 122–26. http://dx.doi.org/10.1007/s10295-004-0124-y.

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Hubber, Andree M., John T. Sullivan i Clive W. Ronson. "Symbiosis-Induced Cascade Regulation of the Mesorhizobium loti R7A VirB/D4 Type IV Secretion System". Molecular Plant-Microbe Interactions® 20, nr 3 (marzec 2007): 255–61. http://dx.doi.org/10.1094/mpmi-20-3-0255.

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The Mesorhizobium loti R7A symbiosis island contains genes encoding a VirB/D4 type IV secretion system (T4SS) similar to that of Agrobacterium tumefaciens. This system has host-dependent effects on symbiosis that probably are due to translocation of two effector proteins, Msi059 and Msi061, into host cells. Here we report that, as in A. tumefaciens, the M. loti vir genes are transcriptionally regulated by a VirA/VirG two-component regulatory system. A virGN54D mutant gene of M. loti caused constitutive expression of lacZ reporter gene fusions to virB1, virD4, msi059, and msi061. Expression of these gene fusions also was activated by a NodD gene product from Rhizobium leguminosarum in the presence of the inducer naringenin, as was a virA∷lacZ fusion. This activation was dependent on a nod box present 851 bp upstream of virA, and a mutant with the nod box deleted formed effective nodules on Leucaena leucocephala, the same symbiotic phenotype as other M.loti vir mutants. In contrast, the wild-type strain formed small, empty nodules whereas a nodD1 mutant was completely Nod¯. These results indicate that the M. loti vir genes are induced in a symbiosis-specific manner that involves a two-tiered regulatory cascade, and that the vir effectors act after Nod factor during infection thread formation.

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Rao, J. R., N. D. Sharma, J. T. G. Hamilton, D. R. Boyd i J. E. Cooper. "Biotransformation of the Pentahydroxy Flavone Quercetin by Rhizobium loti and Bradyrhizobium Strains (Lotus)". Applied and Environmental Microbiology 57, nr 5 (1991): 1563–65. http://dx.doi.org/10.1128/aem.57.5.1563-1565.1991.

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Sami, Dhaoui, Rejili Mokhtar, Mergaert Peter i Mars Mohamed. "Rhizobium leguminosarumsymbiovartrifolii, Ensifer numidicusandMesorhizobium amorphaesymbiovarciceri(orMesorhizobium loti) are new endosymbiotic bacteria ofLens culinarisMedik". FEMS Microbiology Ecology 92, nr 8 (5.06.2016): fiw118. http://dx.doi.org/10.1093/femsec/fiw118.

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Awaya, Jonathan D., Paul M. Fox i Dulal Borthakur. "pyd Genes of Rhizobium sp. Strain TAL1145 Are Required for Degradation of 3-Hydroxy-4-Pyridone, an Aromatic Intermediate in Mimosine Metabolism". Journal of Bacteriology 187, nr 13 (1.07.2005): 4480–87. http://dx.doi.org/10.1128/jb.187.13.4480-4487.2005.

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ABSTRACT Rhizobium sp. strain TAL1145 degrades the Leucaena toxin mimosine and its degradation product 3-hydroxy-4-pyridone (HP). The aim of this investigation is to characterize the Rhizobium genes for HP degradation and transport. These genes were localized by subcloning and mutagenesis on a previously isolated cosmid, pUHR263, containing mid genes of TAL1145 required for mimosine degradation. Two structural genes, pydA and pydB, encoding a metacleavage dioxygenase and a hydrolase, respectively, are required for degradation of HP, and three genes, pydC, pydD, and pydE, encoding proteins of an ABC transporter, are involved in the uptake of HP by TAL1145. These genes are induced by HP, although both pydA and pydB show low levels of expression without HP. pydA and pydB are cotranscribed, while pydC, pydD, and pydE are each transcribed from separate promoters. PydA and PydB show no homology with other dioxygenases and hydrolases in Sinorhizobium meliloti, Mesorhizobium loti, and Bradyrhizobium japonicum. Among various root nodule bacteria, the ability to degrade mimosine or HP is unique to some Leucaena-nodulating Rhizobium strains.

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Goedhart, Joachim, Jean-Jacques Bono i Theodorus W. J. Gadella. "Rapid Colorimetric Quantification of Lipo-chitooligosaccharides from Mesorhizobium loti and Sinorhizobium meliloti". Molecular Plant-Microbe Interactions® 15, nr 9 (wrzesień 2002): 859–65. http://dx.doi.org/10.1094/mpmi.2002.15.9.859.

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Nod factors are lipids with a chitinlike headgroup produced by gram-negative Rhizobium bacteria. These lipo-chitooligosaccharides (LCOs) are essential signaling molecules for accomplishing symbiosis between the bacteria and roots of legume plants. Despite their important role in the Rhizobium-legume interaction, no fast and sensitive Nod factor quantification methods exist. Here, we report two different quantification methods. The first is based on the enzymatic hydrolysis of Nod factors to release N-acetylglucosamine (GlcNAc), which can subsequently be quantified. It is shown that the degrading enzyme, glusulase, releases exactly two GlcNAc units per pentameric nodulation factor from Mesorhizobium loti factor, allowing quantification of LCOs from Mesorhizobium loti. The second method is based on a specific type of Nod factors that are sulfated on the reducing GlcNAc, allowing quantification analogous to the quantification of sulfolipids. Here, a two-phase extraction method is used in the presence of methylene blue, which specifically forms an ion pair with sulfated lipids. The blue ion pair partitions into the organic phase, after which the methylene blue signal can be quantified. To enable Nod factor quantification with this method, the organic phase was modified and the partitioning was evaluated using fluorescent and radiolabeled sulfated Nod factors. It is shown that sulfated LCOs can be quantified with this method, using sodium dodecyl sulfate for calibration. Both methods allow Nod factor quantification in parallel enabling a fast and easy detection of nanomole quantities of Nod factors. Accurate Nod factor quantification will be crucial for characterization and cross-comparison of the affinity for Nod factors of newly identified Nod factor binding proteins or putative Nod factor receptors.

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Gagnon, Hubert, i Ragai K. Ibrahim. "Aldonic Acids: A Novel Family of nod Gene Inducers of Mesorhizobium loti, Rhizobium lupini, and Sinorhizobium meliloti". Molecular Plant-Microbe Interactions® 11, nr 10 (październik 1998): 988–98. http://dx.doi.org/10.1094/mpmi.1998.11.10.988.

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Molecular signals, such as flavonoids (or nonflavonoid type), nod gene-inducers, and bacterial lipochitin oligosac-charides (LCOs) act as modulators of species specificity during early stages of infection in Rhizobium spp.-legume interactions. The fact that signaling in Lupinus albus remains to be determined prompted us to investigate the flavonoid signal responsible for nod gene induction in Rhizobium lupini. A screening method was used based on the measurement of β-galactosidase activity of R. lupini strains harboring nodC::lacZ fusions in the presence of (i) authentic lupin isoflavones, (ii) carbohydrate-like inducers, and (iii) high-pressure liquid chromatography (HPLC)-fractionated lupin seed effusates and root exudates, as putative nod gene inducers. The results indicate that both erythronic and tetronic acids (4-C sugar acids) led to low but significant increases in β-galactosidase activities, compared with the controls. In addition, lupi-wighteone, a monoprenylated isoflavone, exerts a synergistic effect with the carbohydrate-like inducers, compared with other isoflavone treatments. The natural occurrence of aldonic acids in L. albus root exudates and seed effusates has been demonstrated by HPLC analysis. When tested with nodC::lacZ fusions, tetronic acid resulted in nod gene induction in Sinorhizobium meliloti. In addition, a combination of luteolin and tetronic acid promotes further increases in S. meliloti nod gene expression, as shown by β-galactosidase assays. Incorporation studies with [14C]LCO precursors confirmed the inductive role of both erythronic and tetronic acids in promoting LCO biosynthesis in R. lupini cultures, and of tetronic acid in Mesorhizobium loti and S. meliloti. Hydrolysis of the LCOs with various enzymes substantiated their putative identities. These results are discussed in relation to the impact of these unusual signal molecules on our knowledge of flavonoid signaling in Rhizobium-legume symbiosis.

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Agius, F., C. Sanguinetti i J. Monza. "Strain-specific fingerprints of Rhizobium loti generated by PCR with arbitrary and repetitive sequences". FEMS Microbiology Ecology 24, nr 1 (17.01.2006): 87–92. http://dx.doi.org/10.1111/j.1574-6941.1997.tb00425.x.

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Sullivan, J. T., H. N. Patrick, W. L. Lowther, D. B. Scott i C. W. Ronson. "Nodulating strains of Rhizobium loti arise through chromosomal symbiotic gene transfer in the environment." Proceedings of the National Academy of Sciences 92, nr 19 (12.09.1995): 8985–89. http://dx.doi.org/10.1073/pnas.92.19.8985.

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Lieven‐Antoniou, C. A., i T. S. Whittam. "Specificity in the symbiotic association of Lotus corniculatus and Rhizobium loti from natural populations". Molecular Ecology 6, nr 7 (lipiec 1997): 629–39. http://dx.doi.org/10.1046/j.1365-294x.1997.00224.x.

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Bras, Cristina Pacios, Meritxell Alberich Jordá, André H. M. Wijfjes, Marga Harteveld, Nico Stuurman, Jane E. Thomas-Oates i Herman P. Spaink. "A Lotus japonicus Nodulation System Based on Heterologous Expression of the Fucosyl Transferase NodZ and the Acetyl Transferase NolL in Rhizobium leguminosarum". Molecular Plant-Microbe Interactions® 13, nr 4 (kwiecień 2000): 475–79. http://dx.doi.org/10.1094/mpmi.2000.13.4.475.

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Heterologous expression of NodZ and NolL proteins in Rhizobium leguminosarum bv. viciae led to the production of acetyl fucosylated lipo-chitin oligosaccharides (LCOs), indicating that the NolL protein obtained from Mesorhizo-bium loti functions as an acetyl transferase. We show that the NolL-dependent acetylation is specific for the fucosyl penta-N-acetylglucosamine species. In addition, the NolL protein caused elevated production of LCOs. Efficient nodulation of Lotus japonicus by the NodZ/NolL-producing strain was demonstrated. Nodulation efficiency was further improved by the addition of the ethylene inhibitor L-α-(2-aminoethoxyvinyl) glycine (AVG).

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García-de los Santos, Alejandro, Alejandro Morales, Laura Baldomá, Scott R. D. Clark, Susana Brom, Christopher K. Yost, Ismael Hernández-Lucas, Juan Aguilar i Michael F. Hynes. "TheglcBlocus ofRhizobium leguminosarumVF39 encodes an arabinose-inducible malate synthase". Canadian Journal of Microbiology 48, nr 10 (1.10.2002): 922–32. http://dx.doi.org/10.1139/w02-091.

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In the course of a study conducted to isolate genes upregulated by plant cell wall sugars, we identified an arabinose-inducible locus from a transcriptional fusion library of Rhizobium leguminosarum VF39, carrying random insertions of the lacZ transposon Tn5B22. Sequence analysis of the locus disrupted by the transposon revealed a high similarity to uncharacterized malate synthase G genes from Sinorhizobium meliloti, Agrobacterium tumefaciens, and Mesorhizobium loti. This enzyme catalyzes the condensation of glyoxylate and acetyl-CoA to yield malate and CoA and is thought to be a component of the glyoxylate cycle, which allows microorganisms to grow on two carbon compounds. Enzyme assays showed that a functional malate synthase is encoded in the glcB gene of R. leguminosarum and that its expression is induced by arabinose, glycolate, and glyoxylate. An Escherichia coli aceB glcB mutant, complemented with the R. leguminosarum PCR-amplified gene, recovered malate synthase activity. A very similar genome organization of the loci containing malate synthase and flanking genes was observed in R. leguminosarum, S. meliloti, and A. tumefaciens. Pea plants inoculated with the glcB mutant or the wild-type strain showed no significant differences in nitrogen fixation. This is the first report regarding the characterization of a mutant in one of the glyoxylate cycle enzymes in the rhizobia.Key words: Rhizobium, malate synthase, glyoxylate cycle, arabinose metabolism.

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Zakary, Sefatullah, Habeebat Oyewusi i Fahrul Huyop. "Genomic Analysis of Mesorhizobium loti Strain TONO Reveals Dehalogenases for Bioremediation". Journal of Tropical Life Science 11, nr 1 (3.02.2021): 67–77. http://dx.doi.org/10.11594/jtls.11.01.09.

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Halogenated compounds are extensively utilized in different industrial applications such as pesticides and herbicides and cause severe environmental problems because of their toxicity and persistence. Degradation of these compounds by the biological method is a significant method to reduce these recalcitrant. Mesorhizobium loti is important for nitrogen fixation in legume roots. Up to now, there is no report to indicate M. loti can produce dehalogenase enzymes. Thus, a total of twenty-five genomes of M. loti strains from the National Center for Biotechnology Information (NCBI) were analyzed. These strains notably carry dehalogenase genes and were further investigated. The relative ratio of haloalkane and haloacid dehalogenase type II or L-type from all twenty-five genomes was 26% and 74%, respectively, suggesting type II dehalogenase is common. Surprisingly, only M. loti strain TONO carries four dehalogenases and therefore it was further characterized. The chromosome of M. loti strain TONO contains four haloacid dehalogenase type II genes namely, dehLt1 (MLTONO_2099), dehLt2 (MLTONO_3660), dehLt3 (MLTONO_4143), and dehLt4 (MLTONO_6945), and their corresponding enzymes were designated as DehLt1, DehLt2, DehLt3, and DehLt4, respectively. The only haloalkane dehalogenase gene (MLTONO_4828) was located upstream of the dehLt3 gene and its amino acid share 88% identity with DmlA of Mesorhizobium japonicum MAFF 303099. The putative haloacid permease gene designated as dehrPt (MLTONO_0284) was located downstream of the dehLt1 and its amino acids show 69% identity with haloacid permease of Rhizobium sp. RC1. The gene encoding helix-turn-helix (HTH) motif family DNA-binding protein regulator and LysR family transcriptional regulator genes were also identified, possibly for regulatory functions. The genomic studies as such, have good potential to be screened for new type of dehalogenases based on basic molecular structure and functions analysis

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Corvera, Adriana, Danielle Promé, Jean-Claude Promé, Esperanza Martínez-Romero i David Romero. "The nolL Gene from Rhizobium etli Determines Nodulation Efficiency by Mediating the Acetylation of the Fucosyl Residue in the Nodulation Factor". Molecular Plant-Microbe Interactions® 12, nr 3 (marzec 1999): 236–46. http://dx.doi.org/10.1094/mpmi.1999.12.3.236.

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The nodulation factors (Nod factors) of Rhizobium etli and R. loti carry a 4-O-acetyl-L-fucosyl group at the reducing end. It has been claimed, based on sequence analysis, that NolL from R. loti participates in the 4-O-acetylation of the fucosyl residue of the Nod factors, as an acetyl-transferase (D. B. Scott, C. A. Young, J. M. Collins-Emerson, E. A. Terzaghi, E. S. Rockman, P. A. Lewis, and C. E. Pankhurst. Mol. Plant-Microbe Interact. 9:187–197, 1996). Further support for this hypothesis was obtained by studying the production of Nod factors in an R. etli nolL::Km mutant. Chromatographic and mass spectrometry analysis of the Nod factors produced by this strain showed that they lack the acetyl-fucosyl substituent, having a fucosyl group instead. Acetyl-fucosylation was restored upon complementation with a wild-type nolL gene. These results indicate that the nolL gene determines 4-O-acetylation of the fucosyl residue in Nod factors. Analysis of the predicted NolL polypeptide suggests a transmembranal location and that it belongs to the family of integral membrane transacylases (J. M. Slauch, A. A. Lee, M. J. Mahan, and J. J. Mekalanos. J. Bacteriol. 178:5904–5909, 1996). NolL from R. loti was also proposed to function as a transporter; our results show that NolL does not determine a differential secretion of Nod factors from the cell. We also performed plant assays that indicate that acetylation of the fucose conditions efficient nodulation by R. etli of some Phaseolus vulgaris cultivars, as well as of an alternate host (Vigna umbellata).

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Krause, Andrea, Anke Doerfel i Michael Göttfert. "Mutational and Transcriptional Analysis of the Type III Secretion System of Bradyrhizobium japonicum". Molecular Plant-Microbe Interactions® 15, nr 12 (grudzień 2002): 1228–35. http://dx.doi.org/10.1094/mpmi.2002.15.12.1228.

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Sequencing the symbiotic region of Bradyrhizobium japonicum revealed a gene cluster (tts) encoding a type III secretion system (TTSS) that is similar to those found in Mesorhizobium loti MAFF303099 and Rhizobium strain NGR234. In addition to genes that are likely to encode structural core components of the TTSS, the cluster contains several open reading frames that are found exclusively in rhizobia or that are specific to B. japonicum. Depending on the host, mutations within this cluster affected nodulation capacity to different extents. One of the genes likely encodes a transcriptional activator (TtsI) of the two-component regulatory family. Upstream of ttsI, a nod box promoter was identified. Expression of ttsI could be induced by genistein. This induction depended on the transcriptional activator protein NodW as well as the nodD1nodD2nolA gene region. TtsI was found to be involved in transcriptional regulation of the tts gene cluster. Sequence comparison revealed a conserved tts box element within putative promoter regions of several genes. Here, we propose a model of the regulatory cascade leading to the induction of the tts gene cluster.

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Cooper, James E., i J. Raghavendra Rao. "Localized Changes in Flavonoid Biosynthesis in Roots of Lotus pedunculatus after Infection by Rhizobium loti". Plant Physiology 100, nr 1 (1.09.1992): 444–50. http://dx.doi.org/10.1104/pp.100.1.444.

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Vance, Carroll P., Paul H. Reibach i Clive E. Pankhurst. "Symbiotic properties of Lotus pedunculitis root nodules induced by Rhizobium loti and Bradyrhizobium sp. (Lotus)". Physiologia Plantarum 69, nr 3 (marzec 1987): 435–42. http://dx.doi.org/10.1111/j.1399-3054.1987.tb09221.x.

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Monza, J., M. J. Delgado i E. J. Bedmar. "Nitrate reductase and nitrite reductase activity in free-living cells and bacteroids of Rhizobium loti". Plant and Soil 139, nr 2 (styczeń 1992): 203–7. http://dx.doi.org/10.1007/bf00009311.

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Castellane, Tereza Cristina Luque, Alda Maria Machado Bueno Otoboni i Eliana Gertrudes de Macedo Lemos. "Characterization of Exopolysaccharides Produced by Rhizobia Species". Revista Brasileira de Ciência do Solo 39, nr 6 (grudzień 2015): 1566–75. http://dx.doi.org/10.1590/01000683rbcs20150084.

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ABSTRACT Increasing attention has been given, over the past decades, to the production of exopolysaccharides (EPS) from rhizobia, due to their various biotechnological applications. Overall characterization of biopolymers involves evaluation of their chemical, physical, and biological properties; this evaluation is a key factor in understanding their behavior in different environments, which enables researchers to foresee their potential applications. Our focus was to study the EPS produced by Mesorhizobium huakuii LMG14107, M. loti LMG6125, M. plurifarium LMG11892,Rhizobium giardini bv. giardiniH152T, R. mongolense LMG19141, andSinorhizobium (= Ensifer)kostiense LMG19227 in a RDM medium with glycerol as a carbon source. These biopolymers were isolated and characterized by reversed-phase high-performance liquid chromatography (RP-HPLC), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopies. Maximum exopolysaccharide production was 3.10, 2.72, and 2.50 g L-1for the strains LMG6125, LMG19227, and LMG19141, respectively. The purified EPS revealed prominent functional reactive groups, such as hydroxyl and carboxylic, which correspond to a typical heteropolysaccharide. The EPS are composed primarily of galactose and glucose. Minor components found were rhamnose, glucuronic acid, and galacturonic acid. Indeed, from the results of techniques applied in this study, it can be noted that the EPS are species-specific heteropolysaccharide polymers composed of common sugars that are substituted by non-carbohydrate moieties. In addition, analysis of these results indicates that rhizobial EPS can be classified into five groups based on ester type, as determined from the 13C NMR spectra. Knowledge of the EPS composition now facilitates further investigations relating polysaccharide structure and dynamics to rheological properties.

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MacLean, Allyson M., Michelle I. Anstey i Turlough M. Finan. "Binding Site Determinants for the LysR-Type Transcriptional Regulator PcaQ in the Legume Endosymbiont Sinorhizobium meliloti". Journal of Bacteriology 190, nr 4 (30.11.2007): 1237–46. http://dx.doi.org/10.1128/jb.01456-07.

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ABSTRACT LysR-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. In the gram-negative legume endosymbiont Sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the β-ketoadipate pathway are encoded within the pcaDCHGB operon, which is subject to regulation by the LysR-type protein PcaQ. In this work, purified PcaQ was shown to bind strongly (equilibrium dissociation constant, 0.54 nM) to a region at positions −78 to −45 upstream of the pcaD transcriptional start site. Within this region, we defined a PcaQ binding site with dyad symmetry that is required for regulation of pcaD expression in vivo and for binding of PcaQ in vitro. We also demonstrated that PcaQ participates in negative autoregulation by monitoring expression of pcaQ via a transcriptional fusion to lacZ. Although pcaQ homologues are present in many α-proteobacteria, this work describes the first reported purification of this regulator, as well as characterization of its binding site, which is conserved in Agrobacterium tumefaciens, Rhizobium leguminosarum, Rhizobium etli, and Mesorhizobium loti.

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Streit, W. R., R. A. Schmitz, X. Perret, C. Staehelin, W. J. Deakin, C. Raasch, H. Liesegang i W. J. Broughton. "An Evolutionary Hot Spot: the pNGR234b Replicon of Rhizobium sp. Strain NGR234". Journal of Bacteriology 186, nr 2 (15.01.2004): 535–42. http://dx.doi.org/10.1128/jb.186.2.535-542.2004.

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ABSTRACT Rhizobium sp. strain NGR234 has an exceptionally broad host range and is able to nodulate more than 112 genera of legumes. Since the overall organization of the NGR234 genome is strikingly similar to that of the narrow-host-range symbiont Rhizobium meliloti strain 1021 (also known as Sinorhizobium meliloti), the obvious question is why are the spectra of hosts so different? Study of the early symbiotic genes of both bacteria (carried by the SymA plasmids) did not provide obvious answers. Yet, both rhizobia also possess second megaplasmids that bear, among many other genes, those that are involved in the synthesis of extracellular polysaccharides (EPSs). EPSs are involved in fine-tuning symbiotic interactions and thus may help answer the broad- versus narrow-host-range question. Accordingly, we sequenced two fragments (total, 594 kb) that encode 575 open reading frames (ORFs). Comparisons revealed 19 conserved gene clusters with high similarity to R. meliloti, suggesting that a minimum of 28% (158 ORFs) of the genetic information may have been acquired from a common ancestor. The largest conserved cluster carried the exo and exs genes and contained 31 ORFs. In addition, nine highly conserved regions with high similarity to Agrobacterium tumefaciens C58, Bradyrhizobium japonicum USDA110, and Mesorhizobium loti strain MAFF303099, as well as two conserved clusters that are highly homologous to similar regions in the plant pathogen Erwinia carotovora, were identified. Altogether, these findings suggest that ≥40% of the pNGR234b genes are not strain specific and were probably acquired from a wide variety of other microbes. The presence of 26 ORFs coding for transposases and site-specific integrases supports this contention. Surprisingly, several genes involved in the degradation of aromatic carbon sources and genes coding for a type IV pilus were also found.

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Moukoumi, Judicaël, Russell K. Hynes, Timothy J. Dumonceaux, Jennifer Town i Nicolas Bélanger. "Characterization and genus identification of rhizobial symbionts from Caragana arborescens in western Canada". Canadian Journal of Microbiology 59, nr 6 (czerwiec 2013): 399–406. http://dx.doi.org/10.1139/cjm-2013-0158.

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Naturally occurring nitrogen-fixing symbionts from root nodules of caragana (Caragana arborescens) growing in central Saskatchewan were isolated following surface sterilization of caragana root nodules and squashing and spreading of the contents on yeast extract – mannitol medium. The symbiotic nature of the strains was confirmed following inoculation onto surface-sterilized C. arborescens seed in a gnotobiotic Leonard jar system. The Rhizobium isolates from C. arborescens root nodules were intermediate in generation time (g) (mean g of 5 isolates was 6.41 h) compared with the fast growers, Rhizobium leguminosarum NRG457 (g: 4.44 h), Rhizobium tropici 899 (g: 3.19 h), and Sinorhizobium meliloti BALSAC (g: 3.45 h), but they were faster than the slow-growing Bradyrhizobium japonicum USDA 110 (g: 13.86 h) and similar to Mesorhizobium amorphae (g: 7.76 h). Nitrogen derived from fixation by measuring changes in δ15N natural abundance in plant tissue confirmed the effectiveness of the strains; approximately 80% N2 from fixation. Strain identification was carried out by determining the sequences of 3 genes: 16S rRNA-encoding genes, cpn60, and recA. This analysis determined that the symbiotic partner of Canadian C. arborescens belongs to the genus Mesorhizobium and seems more related to M. loti than to previously described caragana symbionts like M. caraganae. This is the first report of Mesorhizobium sp. nodulating C. arborescens in western Canada.

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Báscones, Elena, Juan Imperial, Tomás Ruiz-Argüeso i Jose Manuel Palacios. "Generation of New Hydrogen-RecyclingRhizobiaceae Strains by Introduction of a Novelhup Minitransposon". Applied and Environmental Microbiology 66, nr 10 (1.10.2000): 4292–99. http://dx.doi.org/10.1128/aem.66.10.4292-4299.2000.

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ABSTRACT Hydrogen evolution by nitrogenase is a source of inefficiency for the nitrogen fixation process by the Rhizobium-legume symbiosis. To develop a strategy to generate rhizobial strains with H2-recycling ability, we have constructed a Tn5derivative minitransposon (TnHB100) that contains the ca. 18-kb H2 uptake (hup) gene cluster fromRhizobium leguminosarum bv. viciae UPM791. Bacteroids from TnHB100-containing strains of R. leguminosarum bv. viciae PRE, Bradyrhizobium japonicum, R. etli, and Mesorhizobium loti expressed high levels of hydrogenase activity that resulted in full recycling of the hydrogen evolved by nitrogenase in nodules. Efficient processing of the hydrogenase large subunit (HupL) in these strains was shown by immunoblot analysis of bacteroid extracts. In contrast, Sinorhizobium meliloti,M. ciceri, and R. leguminosarum bv. viciae UML2 strains showed poor expression of the hup system that resulted in H2-evolving nodules. For the latter group of strains, no immunoreactive material was detected in bacteroid extracts using anti-HupL antiserum, suggesting a low level of transcription ofhup genes or HupL instability. A general procedure for the characterization of the minitransposon insertion site and removal of antibiotic resistance gene included in TnHB100 has been developed and used to generate engineered strains suitable for field release.

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JONES, W. T., P. E. MACDONALD, S. D. JONES i C. E. PANKHURST. "Peptidoglycan-bound Polysaccharide Associated with Resistance of Rhizobium loti Strain NZP2037 to Lotus pedunculatus Root Flavolan". Microbiology 133, nr 9 (1.09.1987): 2617–29. http://dx.doi.org/10.1099/00221287-133-9-2617.

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Okazaki, Shin, Saori Okabe, Miku Higashi, Yoshikazu Shimoda, Shusei Sato, Satoshi Tabata, Masatsugu Hashiguchi, Ryo Akashi, Michael Göttfert i Kazuhiko Saeki. "Identification and Functional Analysis of Type III Effector Proteins in Mesorhizobium loti". Molecular Plant-Microbe Interactions® 23, nr 2 (luty 2010): 223–34. http://dx.doi.org/10.1094/mpmi-23-2-0223.

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Mesorhizobium loti MAFF303099, a microsymbiont of the model legume Lotus japonicus, possesses a cluster of genes (tts) that encode a type III secretion system (T3SS). In the presence of heterologous nodD from Rhizobium leguminosarum and a flavonoid naringenin, we observed elevated expression of the tts genes and secretion of several proteins into the culture medium. Inoculation experiments with wild-type and T3SS mutant strains revealed that the presence of the T3SS affected nodulation at a species level within the Lotus genus either positively (L. corniculatus subsp. frondosus and L. filicaulis) or negatively (L. halophilus and two other species). By inoculating L. halophilus with mutants of various type III effector candidate genes, we identified open reading frame mlr6361 as a major determinant of the nodulation restriction observed for L. halophilus. The predicted gene product of mlr6361 is a protein of 3,056 amino acids containing 15 repetitions of a sequence motif of 40 to 45 residues and a shikimate kinase-like domain at its carboxyl terminus. Homologues with similar repeat sequences are present in the hypersensitive-response and pathogenicity regions of several plant pathogens, including strains of Pseudomonas syringae, Ralstonia solanacearum, and Xanthomonas species. These results suggest that L. halophilus recognizes Mlr6361 as potentially pathogen derived and subsequently halts the infection process.

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