Journal articles: 'Rhizobium meliloti'

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NISTE, Monica, Roxana VIDICAN, Ioan ROTAR, and Rodica POP. "The Effect of pH Stress on the Survival of Rhizobium Trifolii and Sinorhizobium Meliloti in Vitro." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 70, no. 2 (2013): 449–50. http://dx.doi.org/10.15835/buasvmcn-agr:9811.

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Nitrogen-fixing symbiotic bacteria known as rhizobia can exist in different soils and adapt to different environmental conditions. The aim of this study was to determine the impact of pH on the growth of Rhizobium trifolii and Sinorhizobium meliloti. Rhizobial species were isolated using yeast extract mannitol agar medium) in which the pH values were adjusted to 5.0, 6.0, 8.0 and 9.0 by adding HCl and NaOH. The optimum pH for rhizobia is neutral or slightly alkaline (pH 8) and they are more sensitive to acidity. Sinorhizobium meliloti developed better in an acid medium compared to Rhizobium trifolii.

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Zurdo-Piñeiro, José Luis, Paula García-Fraile, Raúl Rivas, et al. "Rhizobia from Lanzarote, the Canary Islands, That Nodulate Phaseolus vulgaris Have Characteristics in Common with Sinorhizobium meliloti Isolates from Mainland Spain." Applied and Environmental Microbiology 75, no. 8 (2009): 2354–59. http://dx.doi.org/10.1128/aem.02811-08.

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ABSTRACT The stable, low-molecular-weight (LMW) RNA fractions of several rhizobial isolates of Phaseolus vulgaris grown in the soil of Lanzarote, an island of the Canary Islands, were identical to a less-common pattern found within Sinorhizobium meliloti (assigned to group II) obtained from nodules of alfalfa and alfalfa-related legumes grown in northern Spain. The P. vulgaris isolates and the group II LMW RNA S. meliloti isolates also were distinguishable in that both had two conserved inserts of 20 and 46 bp in the 16S-23S internal transcribed spacer region that were not present in other strains of S. meliloti. The isolates from P. vulgaris nodulated bean but not Medicago sativa, while those recovered from Medicago, Melilotus, and Trigonella spp. nodulated both host legumes. The bean isolates also were distinguished from those of Medicago, Melilotus, and Trigonella spp. by nodC sequence analysis. The nodC sequences of the bean isolates were most similar to those reported for S. meliloti bv. mediterranense and Sinorhizobium fredii bv. mediterranense (GenBank accession numbers DQ333891 and AF217267, respectively). None of the evidence placed the bean isolates from Lanzarote in the genus Rhizobium, which perhaps is inconsistent with seed-borne transmission of Rhizobium etli from the Americas to the Canaries as an explanation for the presence of bean-nodulating rhizobia in soils of Lanzarote.

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Kamal Abadi, Hojjat Safari, Ali Reza Valad Abadi, Jahanfar Daneshian, Hossien Heydari Sharif Abad, and Amin Baghizadeh. "Evaluation of meliloti rhizobium activity effectiveness on quantitative properties of alfalfa by bacterial inoculation in the south-east of Iran." Nexo Revista Científica 33, no. 02 (2020): 725–36. http://dx.doi.org/10.5377/nexo.v33i02.10804.

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In order to investigate the effect of bacterial inoculation on yield, chlorophyll and protein content of alfalfa to obtain economically experimental products in Shahid Zande Rouh Agricultural Training Center in Kerman as a split plot in time based on a completely randomized block design with four replications on the ground Which had not been done before, was done. Bacterial inoculation was at three levels (Rhizobium meliluti, Rhizobium leguminasarum and no inoculation as a control). Bacterial inoculation had a significant effect on all studied traits and caused an increase in chlorophyll content, yield and protein percentage. In terms of fresh forage weight, the first and third crops had the highest yield with the application of Rhizobium meliloti (6 tons per hectare). The highest percentage of protein related to inoculation of Rhizobium meliloti was observed in the second Picking. According to the results of this study, inoculation with Rhizobium meliloti bacteria increases the ability of nitrogen fixation 3 to 4 times compared to the control and improved the alfalfa traits of Bami cultivar in southeastern Iran.

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REUBER, T. L., A. URZAINQUI, J. GLAZEBROOK, J. W. REED, and G. C. WALKER. "Rhizobium meliloti Exopolysaccharides." Annals of the New York Academy of Sciences 646, no. 1 Recombinant D (1991): 61–68. http://dx.doi.org/10.1111/j.1749-6632.1991.tb18564.x.

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Howieson, JG, AD Robson, and LK Abbott. "Calcium modifies pH effects on the growth of acid-tolerant and acid-sensitive Rhizobium meliloti." Australian Journal of Agricultural Research 43, no. 3 (1992): 765. http://dx.doi.org/10.1071/ar9920765.

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The growth of Rhizobium meliloti is sensitive to soil acidity, and its poor growth and survival limits the production from Medicago spp. on acid soils. In the selection of acid tolerant rhizobia for medics, growth in acidified laboratory media has been poorly related to persistence in acid soils. However, the Ca concentration in laboratory media may have been inadequate for growth of some rhizobial strains at low pH. Therefore, acid-tolerant and acid-sensitive strains of R. meliloti were grown in a buffered, defined medium at a range of Ca and P concentrations, and at several pH values. Growth rate was increased by increasing the Ca concentration from 200 to 2000 8M at low (5-70) and moderate (6.50) pH, but not at pH 7.30. Thus, the Ca requirement for the growth of R. meliloti under acid conditions is much higher than previously thought.

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diCenzo, George C., Maryam Zamani, Hannah N. Ludwig, and Turlough M. Finan. "Heterologous Complementation Reveals a Specialized Activity for BacA in the Medicago–Sinorhizobium meliloti Symbiosis." Molecular Plant-Microbe Interactions® 30, no. 4 (2017): 312–24. http://dx.doi.org/10.1094/mpmi-02-17-0030-r.

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The bacterium Sinorhizobium meliloti Rm2011 forms N2-fixing root nodules on alfalfa and other leguminous plants. The pSymB chromid contains a 110-kb region (the ETR region) showing high synteny to a chromosomally located region in Sinorhizobium fredii NGR234 and related rhizobia. We recently introduced the ETR region from S. fredii NGR234 into the S. meliloti chromosome. Here, we report that, unexpectedly, the S. fredii NGR234 ETR region did not complement deletion of the S. meliloti ETR region in symbiosis with Medicago sativa. This phenotype was due to the bacA gene of NGR234 not being functionally interchangeable with the S. meliloti bacA gene during M. sativa symbiosis. Further analysis revealed that, whereas bacA genes from S. fredii or Rhizobium leguminosarum bv. viciae 3841 failed to complement the Fix− phenotype of a S. meliloti bacA mutant with M. sativa, they allowed for further developmental progression prior to a loss of viability. In contrast, with Melilotus alba, bacA from S. fredii and R. leguminosarum supported N2 fixation by a S. meliloti bacA mutant. Additionally, the S. meliloti bacA gene can support N2 fixation of a R. leguminosarum bacA mutant during symbiosis with Pisum sativum. A phylogeny of BacA proteins illustrated that S. meliloti BacA has rapidly diverged from most rhizobia and has converged toward the sequence of pathogenic genera Brucella and Escherichia. These data suggest that the S. meliloti BacA has evolved toward a specific interaction with Medicago and highlights the limitations of using a single model system for the study of complex biological topics.

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Barran, L. R., E. S. P. Bromfield, V. Rastogi, S. T. Whitwill, and R. Wheatcroft. "Transposition and copy number of insertion sequence ISRm1 are not correlated with symbiotic performance of Rhizobium meliloti from two field sites." Canadian Journal of Microbiology 37, no. 7 (1991): 576–79. http://dx.doi.org/10.1139/m91-097.

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The insertion sequence ISRm1 frequently occurs in Rhizobium meliloti and is a potential mutagen. Data for the frequency of ISRm1 transposition in the commercial inoculant strain SU47 (containing eight copies of IsRm1) indicate that this insertion sequence does not significantly affect the ability of SU47 to occupy nodules of alfalfa (Medicago sativa L.) grown at two field sites. Thirty representative isolates from the indigenous population of R. meliloti at each of these sites contained from 0 to 10 copies of IsRm1; there was no significant correlation between insertion sequence copy number and nodulating competitiveness, symbiotic effectiveness, or frequency of occurrence of indigenous rhizobia in nodules of plants grown at these sites. Collectively, these data suggest that ISRm1 has little impact on the stability of agriculturally important properties of R. meliloti from the two field sites, despite its potential as a mutagen. Key words: insertion element, symbiotic effectiveness, competitiveness, Rhizobium meliloti, indigenous populations.

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McKhann, Heather I., Nancy L. Paiva, Richard A. Dixon, and Ann M. Hirsch. "Chalcone Synthase Transcripts Are Detected in Alfalfa Root Hairs Following Inoculation with Wild-Type Rhizobium meliloti." Molecular Plant-Microbe Interactions® 10, no. 1 (1997): 50–58. http://dx.doi.org/10.1094/mpmi.1997.10.1.50.

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Flavonoids are involved in a number of critical events in the interaction between nitrogen-fixing bacteria and legumes. To get a better understanding of the importance of flavonoids in the earliest stages of the alfalfa-Rhizobium meliloti symbiosis, we followed the expression of two chal-cone synthase (CHS) gene family members as well as of chalcone isomerase (CHI) and isoflavone reductase (IFR) genes. CHS transcripts increased 2 to 4 dpi (days post-inoculation) with wild-type rhizobia, but not after inoculation with the heterologous R. leguminosarum bv. trifolii or with an exopolysaccharide (exo) mutant of R. meliloti. CHS transcripts were detected in the root hairs and epidermal cells of the root hair zone, and infrequently in nodule pri-mordia. Insignificant CHI and IFR mRNA accumulation over control levels was observed in response to rhizobial inoculation. The slight increase in CHS transcript accumulation following wild-type R. meliloti inoculation was correlated with an observed increase in root flavonoid content as well as a change in the nod gene-inducing activity of the root exudate. The nod gene-inducing flavonoids exuded from wild-type rhizobia-inoculated roots were identified as 4′, 7-dihydroxyflavone and 4, 4′ dihydroxy-2′-methoxychalcone. Although there was a slight increase over the uninoculated controls in the level of medicarpin-3-O-glucoside 6″-O-malonate (MGM) in extracts of roots inoculated with rhizobia, IFR transcript accumulation was not significantly elevated over that of the controls. Moreover, no medicarpin aglycone was detected in the inoculated roots. Thus, although inoculation with wild-type rhizobia triggers some of the genes induced during an interaction between a host and a pathogen, the expression of these genes in the Rhizobium-legume interaction is at a very low level, suggesting that rhizobia have evolved a mechanism(s) to avoid triggering the host's defense responses.

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NISTE, Monica, Roxana VIDICAN, Ioan ROTAR, and Rodica POP. "Characterization of the growth of Rhizobium trifolii and Sinorhizobium meliloti in different culture media." Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture 70, no. 1 (2013): 80–86. http://dx.doi.org/10.15835/buasvmcn-agr:9559.

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Legumes have the ability to form symbiotic interactions with soil bacteria, called rhizobia. Bacteria of the genus Rhizobium are able to convert atmospheric nitrogen into ammonia when compounds are exchanged between the bacteroid and its plant host. The present study describes the characterization of Rhizobium strains isolated from root nodules of Trifolium pratense and Medicago sativa grown in a greenhouse. The main objective of the experiment was to identify which medium is more suitable for the development of different strains of rhizobia. The Rhizobium strains are rod shaped, Gram negative and mucus producing. The rhizobia were identified and isolated using different media yeast extract mannitol agar (YEMA) containing Congo red, and a medium including boron (B), an essential micronutrient. The Petri plates were incubated at 28ÂºC and inspected three days after the inoculation. The colony morphology was analysed based on type, appearance, transparency, colour and the effectiveness of boron on Rhizobium growth.

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Biederbeck, V. O., and H. J. Geissler. "Effect of storage temperatures on Rhizobium meliloti survival in peat- and clay-based inoculants." Canadian Journal of Plant Science 73, no. 1 (1993): 101–10. http://dx.doi.org/10.4141/cjps93-013.

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Legume growers and extension agents require advice on optimum conditions under which inoculants may be stored without deterioration of rhizobia or the effectiveness of the inoculant. This study was conducted to determine effects of storage duration and temperature on survival of Rhizobium meliloti in two inoculant carriers, one with a peat base and the other with a clay base. Inoculant subsamples were placed in polyethylene bags, then packaged into plastic containers and stored in wooden boxes at either −23 °C (freezer), 4 °C (refrigerator), or room temperature (21–33 °C). Before and after storage for 0.5, 3, 6, 9, 12, 15 and 20 mo, samples were analyzed for surviving rhizobia by most probable number (MPN) plant-infection technique using plastic pouches with seedlings of alfalfa (Medicago sativa L. ’Algonquin’). These counts showed no significant reduction of rhizobial viability in either inoculant at any temperature over the 20-mo study. The surprising lack of population decreases was attributed partly to the wide span between the confidence limits of MPN estimates (at P = 0.05) and partly to the effectiveness of the protective packaging in preventing any desiccation or acidification of the inoculants. Throughout the experiment pH remained unchanged at 6.8 and 8.5 and moisture content at 12.3 and 3.0% in the peat-base and clay-base inoculants, respectively. Nodule color and size indicated that symbiotic effectiveness was not affected by storage temperature. Counts, when averaged across temperatures, showed rhizobial populations remained constant around 1.3 × 109 cells g−1 peat and 1.1 × 108 cells g−1 clay. Re-testing of R. meliloti inoculants stored for up to 10 yr at 4 °C, after earlier regulatory testing, showed no significant viability reductions in any product stored < 7 yr and in some products stored for as long as 10 yr. The results indicated that rhizobial populations could be maintained at levels much above the regulatory minimum MPN (103 seed−1), which would be of critical importance when forage legumes are grown under adverse soil conditions and inoculation is required. Key words: Rhizobium meliloti, inoculant storage, temperature effects, carrier effects, MPN plant-infection technique, inoculant quality control

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Fitzmaurice, Ann Marie, and Fergal O'Gara. "Glutamate catabolism in Rhizobium meliloti." Archives of Microbiology 155, no. 5 (1991): 422–27. http://dx.doi.org/10.1007/bf00244956.

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Watson, R. J., V. K. Rastogi, and Y. K. Chan. "Aspartate transport in Rhizobium meliloti." Journal of General Microbiology 139, no. 6 (1993): 1315–23. http://dx.doi.org/10.1099/00221287-139-6-1315.

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Banfalvi, Zsofia, Eva Kondorosi, and Adam Kondorosi. "Rhizobium meliloti carries two megaplasmids." Plasmid 13, no. 2 (1985): 129–38. http://dx.doi.org/10.1016/0147-619x(85)90065-4.

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George, M. L. C., J. P. W. Young, and D. Borthakur. "Genetic characterization of Rhizobium sp. strain TAL1145 that nodulates tree legumes." Canadian Journal of Microbiology 40, no. 3 (1994): 208–15. http://dx.doi.org/10.1139/m94-034.

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Rhizobium sp. strain TALI 145 nodulates Leucaena ieucocephaia and Phaseolus vulgaris, in addition to a wide range of tropical tree legumes. Six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. The common nod and nifA genes were situated approximately 17 kb apart, with the nodlJ genes in between. These clones enabled a derivative of TAL1145 carrying a partially deleted pSym to form ineffective nodules on both leucaena and bean, and a similar derivative of Rhizobium etli TAL182 to form ineffective nodules on bean. When two representative clones, pUHR9 and pUHR114, were each transferred to wild-type rhizobial strains, they allowed ineffective nodulation by Rhizobium meliloti on both leucaena and bean and by Rhizobium leguminosarum bv. viciae on bean. Transconjugants of R. leguminosarum bv. trifolii formed effective nodules on leucaena and ineffective nodules on bean. Tn5 mutagenesis of the symbiosis region resulted in a variety of nodulation and fixation phenotypes on leucaena and bean. On the basis of 16S rRNA sequences, TAL1145 was found to be distinct from both R. tropici and NGR234, the two groups of leucaena symbionts that were previously described.Key words: Rhizobium, Leucaena leucocephala, nodulation, nitrogen fixation.

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Abola, A. Pia, Michael G. Willits, Richard C. Wang, and Sharon R. Long. "Reduction of Adenosine-5′-Phosphosulfate Instead of 3′-Phosphoadenosine-5′-Phosphosulfate in Cysteine Biosynthesis by Rhizobium meliloti and Other Members of the Family Rhizobiaceae." Journal of Bacteriology 181, no. 17 (1999): 5280–87. http://dx.doi.org/10.1128/jb.181.17.5280-5287.1999.

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ABSTRACT We have cloned and sequenced three genes from Rhizobium meliloti (Sinorhizobium meliloti) that are involved in sulfate activation for cysteine biosynthesis. Two of the genes display homology to the Escherichia coli cysDN genes, which code for an ATP sulfurylase (EC 2.7.7.4 ). The third gene has homology to the E. coli cysH gene, a 3′-phosphoadenosine-5′-phosphosulfate (PAPS) reductase (EC 1.8.99.4 ), but has greater homology to a set of genes found in Arabidopsis thaliana that encode an adenosine-5′-phosphosulfate (APS) reductase. In order to determine the specificity of the R. meliloti reductase, the R. meliloti cysH homolog was histidine tagged and purified, and its specificity was assayed in vitro. Like the A. thaliana reductases, the histidine-tagged R. meliloti cysH gene product appears to favor APS over PAPS as a substrate, with a Km for APS of 3 to 4 μM but a Km for PAPS of >100 μM. In order to determine whether this preference for APS is unique to R. meliloti among members of the familyRhizobiaceae or is more widespread, cell extracts fromR. leguminosarum, Rhizobium sp. strain NGR234,Rhizobium fredii (Sinorhizobium fredii), andAgrobacterium tumefaciens were assayed for APS or PAPS reductase activity. Cell extracts from all four species also preferentially reduce APS over PAPS.

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Selenska-Trajkowa, S., G. Radewa, and K. Markov. "Comparison between Rhizobium galegae and Rhizobium meliloti plasmid contents." Letters in Applied Microbiology 10, no. 3 (1990): 123–26. http://dx.doi.org/10.1111/j.1472-765x.1990.tb00097.x.

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Fisher, Robert F., Janice K. Tu, and Sharon R. Long. "Conserved Nodulation Genes in Rhizobium meliloti and Rhizobium trifolii." Applied and Environmental Microbiology 49, no. 6 (1985): 1432–35. http://dx.doi.org/10.1128/aem.49.6.1432-1435.1985.

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Herrera-Cervera, Jose A., Julio M. Sanjuan-Pinilla, Jose Olivares, and Juan Sanjuan. "Cloning and Identification of Conjugative Transfer Origins in the Rhizobium meliloti Genome." Journal of Bacteriology 180, no. 17 (1998): 4583–90. http://dx.doi.org/10.1128/jb.180.17.4583-4590.1998.

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ABSTRACT A simple approach was used to identify Rhizobium meliloti DNA regions with the ability to convert a nontransmissible vector into a mobilizable plasmid, i.e., to contain origins of conjugative transfer (oriT,mob). RecA-defective R. meliloti merodiploid populations, where each individual contained a hybrid cosmid from anR. meliloti GR4 gene library, were used as donors en masse in conjugation with another R. meliloti recipient strain, selecting transconjugants for vector-encoded antibiotic resistance. Restriction analysis of cosmids isolated from individual transconjugants resulted in the identification of 11 nonoverlapping DNA regions containing potential oriTs. Individual hybrid cosmids were confirmed to be mobilized from the originalrecA donors at frequencies ranging from 10−2to 10−5 per recipient cell. DNA hybridization experiments showed that seven mob DNA regions correspond to plasmid replicons: four on symbiotic megaplasmid 1 (pSym1), one on pSym2, and another two on each of the two cryptic plasmids harbored by R. meliloti GR4. Another three mob clones could not be located to any plasmid and were therefore preliminarily assigned to the chromosome. With this strategy, we were able to characterize theoriT of the conjugative plasmid pRmeGR4a, which confirmed the reliability of the approach to select for oriTs. Moreover, transfer of the 11 mob cosmids from R. meliloti into Escherichia coli occurred at frequencies as high as 10−1, demonstrating the R. meliloti gene transfer capacity is not limited to the familyRhizobiaceae. Our results show that the R. meliloti genome contains multiple oriTs that allow efficient DNA mobilization to rhizobia as well as to phylogenetically distant gram-negative bacteria.

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Debellé, F., F. Maillet, J. Vasse, et al. "Interference between Rhizobium meliloti and Rhizobium trifolii nodulation genes: genetic basis of R. meliloti dominance." Journal of Bacteriology 170, no. 12 (1988): 5718–27. http://dx.doi.org/10.1128/jb.170.12.5718-5727.1988.

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Howieson, JG, and MA Ewing. "Acid tolerance in the Rhizobium meliloti - Medicago symbiosis." Australian Journal of Agricultural Research 37, no. 1 (1986): 55. http://dx.doi.org/10.1071/ar9860055.

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Several strains of Rhizobium meliloti that originated from acid soils in Sardinia, Italy, were markedly superior in colonizing a moderately acid loamy sand (pH 5.0 in 1:5 0.01 M CaCl2) than two Australian commercial inoculant strains (U45 and CC169), and a group of strains that originated from alkaline soils in Syria and Iraq. Six Medicago hosts also varied greatly in their ability to achieve nodulation in this soil. M. polymorpha and M. murex were far superior in this respect to M. littoralis, M. truncatula and M. tornata. The most acid-tolerant strains of R. meliloti, WSM419 and WSM413, were able to nodulate a high proportion of plants of M. polymorpha and M. murex sown in the second year between 11 and 20 cm from the point of introduction of the rhizobia into the soil the previous year. It is suggested that these more saprophytically competent isolates of R. meliloti, combined with the species of Medicago more able to nodulate readily in acid soil, will extend the range of soils suitable for successful regenerative growth of these species.

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Athar, Mohammad, and Douglas A. Johnson. "The influence of soil water potential on the growth and survival of alfalfa rhizobia in the soil." Acta Societatis Botanicorum Poloniae 66, no. 1 (2014): 55–59. http://dx.doi.org/10.5586/asbp.1997.008.

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Growth and survival of alfalfa rhizobia (<em>Rhizobium meliloti</em> Dang.) from Pakistan and Nepal were studied in vials filled with sterile soil maintained at -0.03, -1.0, and -1.5 MPa. The main effects of water level, rhizobial strains and length of exposure to desiccation and their interactions showed a highly significant (P S 0.001) effect on the number of rhizobia g<sup>-1</sup> of soil. Growth and survival of rhizobia were highest in soil at -0.03 MPa followed by soil at -1.0 and -1.5 MPa. Highest cell counts were observed for strain UL 136 followed by strain UL 222 and the lowest was for strain UL 61. Two rhizobial strains (UL 136 and UL 222) were most tolerant to desiccation and showed highest growth and survival under low water potential. These two strains probably could be used as inoculants for alfalfa production under arid and semiarid environments.

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Rebah, Faouzi Ben, Rajeshwar D. Tyagi, Danielle Prévost, and Rao Y. Surampalli. "Wastewater Sludge as a New Medium for Rhizobial Growth." Water Quality Research Journal 37, no. 2 (2002): 353–70. http://dx.doi.org/10.2166/wqrj.2002.022.

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Abstract The objective of this study was to demonstrate that municipal and industrial wastewater sludges could be used as a sole raw material to sustain growth of rhizobia. Growth of two different groups of rhizobium (fast growing: Sinorhizobium meliloti, Rhizobium leguminosarum bv viciae; and slow growing: Bradyrhizobium japonicum and Bradyrhizobium elkanii) was tested on primary, secondary and mixed sludges obtained from different wastewater treatment plants. The results obtained in Erlenmeyer flasks indicated that slow- and fast-growing rhizobia grew well in sludge. Generally, the number of cells of rhizobia exceeds 1 × 109 cfu/mL in 72 h. The composition of sludges varies with the sludge type and origin. The sludge composition affected the generation time, cell yield and nodulation index. Higher solids concentration tended to give higher generation time. The high sludge metals concentration did not affect the growth kinetics of rhizobia. However, primary sludge could inhibit cell growth. Acid, alkaline and oxidative pre-treatments increased the primary sludge biodegradability and consequently the cell count of S. meliloti. Pre-treatment of pulp and paper sludge with NaOH enhanced the bacterial cell concentration to a maximum 1 × 1010 cfu/mL. Sludge pre-treatment decreased the generation time and reduced the process time.

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Barnett, Melanie J., Jean A. Swanson, and Sharon R. Long. "Multiple Genetic Controls on Rhizobium meliloti syrA, a Regulator of Exopolysaccharide Abundance." Genetics 148, no. 1 (1998): 19–32. http://dx.doi.org/10.1093/genetics/148.1.19.

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Abstract Exopolysaccharides (EPS) are produced by a wide assortment of bacteria including plant pathogens and rhizobial symbionts. Rhizobium meliloti mutants defective in EPS production fail to invade alfalfa nodules. Production of EPS in R. meliloti is likely controlled at several levels. We have characterized a new gene of this regulatory circuit. syrA was identified by its ability to confer mucoid colony morphology and by its ability to suppress the colonial phenotype of an exoD mutant. Here we show that syrA encodes a 9-kD hydrophobic protein that has sequence similarity to two other EPS regulatory proteins: ExoX of Rhizobium NGR234 and R. meliloti, and Psi of R. leguminosarum bv. phaseoli. The syrA transcription start site lies 522 nucleotides upstream of a non-canonical TTG start codon. The syrA promoter region is similar to the promoter region of the nodulation regulatory protein, nodD3. We found that in free-living bacteria, syrA expression is activated by the regulatory locus, syrM, but not by nodD3. In planta, syrM is not required for expression of syrA. Instead, expression of the nitrogen fixation (nifHDKE) genes upstream of syrA plays a role. Specific and distinct sets of genetic controls may operate at different times during nodule invasion.

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Elslahi, Randa H., Awad G. Osman, Ashraf M. Sherif, and Adil A. Elhussein. "Comparative study of the fungicide Benomyl toxicity on some plant growth promoting bacteria and some fungi in pure cultures." Interdisciplinary Toxicology 7, no. 1 (2014): 12–16. http://dx.doi.org/10.2478/intox-2014-0002.

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Abstract Six laboratory experiments were carried out to investigate the effect of the fungicide Benomyl on pure cultures of some plant growth promoting bacteria (PGPB) and some fungi. The highest LD50 was recorded for Bacillus circulans and proved to be the most resistant to the fungicide, followed by Azospirillum braziliense, while Penicillium sp. was the most affected microorganism. LD50 values for the affected microorganisms were in 21-240 orders of magnitude lower in comparison with the LD50 value for Azospirillum braziliense. The results indicate a strong selectivity for Benomyl against Rhizobium meliloti and Penicillium sp. when compared to other microorganisms tested. The highest safety coefficient was recorded for Bacillus circulans followed by Azospirillum braziliense, while Rhizobium meliloti, showed the lowest safety coefficient value compared to other bacteria. The lowest toxicity index was recorded for Bacillus circulans and Azospirillum braziliense. The slope of the curves for Bacillus sp. and Rhizobium meliloti was steeper than that of the other curves, suggesting that even a slight increase of the dose of the fungicide can cause a very strong negative effect. In conclusion, Benomyl could be applied without restriction when using inocula based on growth promoting bacteria such as symbiotic nitrogen fixers (Rhizobium meliloti), non-symbiotic nitrogen fixers (Azospirillum braziliense) or potassium solibilizers (Bacillus circulans), given that the fungicide is applied within the range of the recommended field dose.

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Rumiantseva, I. B., V. N. Yerko, and B. V. Simarov. "Cloning of genome of Rhizobium meliloti in vectors of different types." Biopolymers and Cell 13, no. 3 (1997): 222–31. http://dx.doi.org/10.7124/bc.000483.

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Courtois, J., B. Courtois, and J. Guillaume. "High-frequency transformation of Rhizobium meliloti." Journal of Bacteriology 170, no. 12 (1988): 5925–27. http://dx.doi.org/10.1128/jb.170.12.5925-5927.1988.

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27

Maŀek, Wanda. "Chemotaxis in Rhizobium meliloti strain L5.30." Archives of Microbiology 152, no. 6 (1989): 611–12. http://dx.doi.org/10.1007/bf00425496.

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28

Glazebrook, Jane, Jason W. Reed, T. Lynne Reuber, and Graham C. Walker. "Genetic analyses of Rhizobium meliloti exopolysaccharides." International Journal of Biological Macromolecules 12, no. 2 (1990): 67–70. http://dx.doi.org/10.1016/0141-8130(90)90055-f.

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Burkardt, Beate, Dagmar Schillik, and A. Pühler. "Physical characterization of Rhizobium meliloti megaplasmids." Plasmid 17, no. 1 (1987): 13–25. http://dx.doi.org/10.1016/0147-619x(87)90004-7.

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30

Rightmyer, Adriana P., and Sharon R. Long. "Pseudonodule Formation by Wild-Type and Symbiotic Mutant Medicago truncatula in Response to Auxin Transport Inhibitors." Molecular Plant-Microbe Interactions® 24, no. 11 (2011): 1372–84. http://dx.doi.org/10.1094/mpmi-04-11-0103.

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Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones play key roles in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATI) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. M. truncatula mutants defective for rhizobial Nod factor signal transduction still formed pseudonodules in response to ATI. However, a M. truncatula ethylene-insensitive supernodulator, sickle 1-1, did not form pseudonodules in response to TIBA, suggesting that the ethylene response pathway is involved in ATI-induced pseudonodule formation. We compared the transcriptional responses of M. truncatula roots treated with ATI to roots inoculated with Sinorhizobium meliloti. Some genes showed consistently parallel expression in ATI-induced and Rhizobium-induced nodules. For other genes, the transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment was in the opposite direction to roots treated with S. meliloti; then, by 21 days, the transcriptional patterns for the two conditions became similar. We silenced 17 genes that were upregulated in both ATI and S. meliloti treatments to determine their effect on nodule formation. Some gene-silenced roots showed a decrease in nodulation efficiency, suggesting a role in nodule formation but not in later nodule functions.

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Bardin, Sylvie D., and Turlough M. Finan. "Regulation of Phosphate Assimilation in Rhizobium (Sinorhizobium) meliloti." Genetics 148, no. 4 (1998): 1689–700. http://dx.doi.org/10.1093/genetics/148.4.1689.

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Abstract We report the isolation of phoB and phoU mutants of the bacterium Rhizobium (Sinorhizobium) meliloti. These mutants form N2-fixing nodules on the roots of alfalfa plants. R. meliloti mutants defective in the phoCDET (ndvF) encoded phosphate transport system grow slowly in media containing 2 mm Pi, and form nodules which fail to fix nitrogen (Fix−). We show that the transfer of phoB or phoU insertion mutations into phoC mutant strains restores the ability of these mutants to: (i) form normal N2-fixing root-nodules, and (ii) grow like the wild type in media containing 2 mm Pi. We also show that expression of the alternate orfA pit encoded Pi transport system is negatively regulated by the phoB gene product, whereas phoB is required for phoCDET expression. We suggest that in R. meliloti cells growing under Pi limiting conditions, PhoB protein activates phoCDET transcription and represses orfA pit transcription. Our results suggest that there are major differences between the Escherichia coli and R. meliloti phosphate regulatory systems.

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32

Lentzsch, Peter, and Gerhard Miksch. "Detection of uptake hydrogenase in Rhizobium leguminosarum and Rhizobium meliloti." Zentralblatt für Mikrobiologie 143, no. 4 (1988): 269–74. http://dx.doi.org/10.1016/s0232-4393(88)80015-5.

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33

Bromfield, E. S. P., and L. R. Barran. "Promiscuous nodulation of Phaseolus vulgaris, Macroptilium atropurpureum, and Leucaena leucocephala by indigenous Rhizobium meliloti." Canadian Journal of Microbiology 36, no. 5 (1990): 369–72. http://dx.doi.org/10.1139/m90-065.

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Thirty-three isolates of indigenous Rhizobium meliloti, either possessing cryptic plasmids that hybridize to probes for symbiotic genes or lacking a 1500-kb megaplasmid band in Eckhardt gels, were tested for infectivity on 10 legume species grown under axenic conditions. A previous study had shown that all but two isolates were symbiotically effective with Medicago sativa. All indigenous isolates and two reference strains of R. meliloti induced nodules which were symbiotically ineffective on Trigonella foenum-graecum (100% plants nodulated) and Phaseolus vulgaris (40 to 100% plants nodulated). Eighteen indigenous isolates of R. meliloti elicited ineffective nodules on Macroptilium atropurpureum (2 to 25% plants nodulated) and Leucaena leucocephala (11 to 75% plants nodulated). The identity of single colony nodule isolates from each R. meliloti inoculant and host combination was verified by phage typing and analysis of plasmid profiles; tests with subsamples of these isolates showed that all were capable of nodulating M. sativa. There was no apparent relationship between the host range of indigenous R. meliloti and either the presence of cryptic plasmids that hybridize to probes for symbiotic genes or the absence of a megaplasmid band in Eckhardt gels. The data suggest that nodulation promiscuity may be a relatively common characteristic of R. meliloti. Key words: host range, Rhizobium meliloti, Leucaena, Macroptilium, Phaseolus.

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34

Itzigsohn, R., Y. Kapulnik, Y. Okon, and A. Dovrat. "Physiological and morphological aspects of interactions between Rhizobium meliloti and alfalfa (Medicago sativa) in association with Azospirillum brasilense." Canadian Journal of Microbiology 39, no. 6 (1993): 610–15. http://dx.doi.org/10.1139/m93-088.

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In a 50-L pot experiment with Medicago sativa grown under nonsterile conditions, a combined treatment of Azospirillum and Rhizobium was measured against soil inoculated with Rhizobium or Azospirillum alone or a control with a low background level of autochthonous rhizobia. The combined treatment significantly increased the shoot length and weight at 6 weeks and the regrowth shoot weight at 14 weeks when compared with the treatment with Rhizobium alone. In 1.5-L pots in which gnotobiotic conditions were maintained, the combined treatment led to more nodules on the main root at intermediate Rhizobium concentrations, and a greater root surface area at intermediate and high Rhizobium concentrations after 2 weeks but not after 4 weeks. In pouch-grown seedlings, plants were inoculated with either Rhizobium alone or in combination with Azospirillum or applied together with a flavonoid, luteolin (a nodulation gene inducer), or with a cytokinin, benzyl adenine. Luteolin had similar effects to those of Azospirillum in increasing the main root nodule number and the total nodule number. With Fahraeus slides, a significant increase was observed in the number of root hairs and the root diameter in the presence of Azospirillum as compared with the control and Rhizobium alone. There was no increase in the total number of infection threads; however, the combined treatment caused a significant decrease in the percentage of infected root hairs.Key words: Rhizobium, Azospirillum, Medicago, flavonoid, inoculation.

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Prévost and E. S P. Bromfield, D. "Diversity of symbiotic rhizobia resident in Canadian soils." Canadian Journal of Soil Science 83, Special Issue (2003): 311–19. http://dx.doi.org/10.4141/s01-066.

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The dependency of agriculture on nitrogen fertilizer inputs is associated with adverse effects on the environment and human health. The importance of biological nitrogen fixation by rhizobia in symbiotic association with legumes is underscored by its potential to reduce or replace chemical fertilizer inputs. This paper reviews research on the diversity of the symbiotic rhizobia resident in Canadian soils. Research has focussed on phenotypic and genotypic variation (e.g., nitrogen fixing efficacy, nodulating competitiveness, host range, adaptation to cool climate) within rhizobial species with the objective of selecting efficient strains for use in inoculants for legume crops. The genetic diversity of rhizobia resident in Canadian soils has been reported only for Sinorhizobium meliloti, Rhizobium leguminosarum and Mesorhizobium spp. There is a need for further studies on populations of other rhizobial species, particularly those associated with native legumes. Exploiting the diversity present in natural soil populations via selection and genetic manipulation should permit the development of superior strains for use in legume inoculants. Other rhizobial traits that may be exploited include plant growth-promoting activity and ability to degrade pollutants. Key words: Symbiotic rhizobia, diversity, Canadian soils

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36

Boncompagni, Eric, Magne Østerås, Marie-Christine Poggi, and 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, no. 5 (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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37

Rastogi, V. K., E. S. P. Bromfield, S. T. Whitwill, and L. R. Barran. "A cryptic plasmid of indigenous Rhizobium meliloti possesses reiterated nodC and nifE genes and undergoes DNA rearrangement." Canadian Journal of Microbiology 38, no. 6 (1992): 563–68. http://dx.doi.org/10.1139/m92-092.

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Indigenous Rhizobium meliloti were previously characterized on the basis of plasmid profiles and phage sensitivity patterns (phage types). Rhizobium meliloti 1076, which contained two cryptic plasmids, was one of four isolates comprising phage type 23. In this study, the large cryptic plasmid pVS1(size >500 b) was transferred from isolate 1076 into the plasmid-free strain of Agrobacterium tumefaciens UBAPF1. This plasmid contained nucleotide sequences homologous to genes for nodulation (nodB, nodC) and nitrogen fixation (nifH, nifD, nifK, nifE). Cosmid clones possessing the nod and nif homologous sequences, which had been selected from a genomic bank of A. tumefaciens UBAPF1 containing pVS1, complemented R. meliloti nodC and nifE mutants, respectively. These results demonstrate that the nodC and nifE homologous sequences are functionally expressed. Three of four isolates comprising phage type 23 possessed a megaplasmid band in agarose gels characteristic of R. meliloti, as well as two cryptic plasmids. The fourth isolate (No. 323) lacked the large cryptic plasmid corresponding to pVS1, but instead showed a band of lesser mobility than that of the megaplasmids. Nevertheless, its restricted genomic DNA retained the nodC and nifE hybridizing fragments characteristic of pVS1, indicating that the cryptic plasmid has undergone DNA rearrangement. Key words: Rhizobium, plasmid, reiteration, genes, rearrangement.

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38

Swanson, J. A., J. T. Mulligan, and S. R. Long. "Regulation of syrM and nodD3 in Rhizobium meliloti." Genetics 134, no. 2 (1993): 435–44. http://dx.doi.org/10.1093/genetics/134.2.435.

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Abstract The early steps of symbiotic nodule formation by Rhizobium on plants require coordinate expression of several nod gene operons, which is accomplished by the activating protein NodD. Three different NodD proteins are encoded by Sym plasmid genes in Rhizobium meliloti, the alfalfa symbiont. NodD1 and NodD2 activate nod operons when Rhizobium is exposed to host plant inducers. The third, NodD3, is an inducer-independent activator of nod operons. We previously observed that nodD3 carried on a multicopy plasmid required another closely linked gene, syrM, for constitutive nod operon expression. Here, we show that syrM activates expression of the nodD3 gene, and that nodD3 activates expression of syrM. The two genes constitute a self-amplifying positive regulatory circuit in both cultured Rhizobium and cells within the symbiotic nodule. We find little effect of plant inducers on the circuit or on expression of nodD3 carried on pSyma. This regulatory circuit may be important for regulation of nod genes within the developing nodule.

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Brockwell, J., A. Pilka, and RA Holliday. "Soil pH is a major determinant of the numbers of naturally occurring Rhizobium meliloti in non-cultivated soils in central New South Wales." Australian Journal of Experimental Agriculture 31, no. 2 (1991): 211. http://dx.doi.org/10.1071/ea9910211.

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Measurements were made of soil pH, frequency of occurrence of annual species of Medicago (medics) and populations of Rhizobium meliloti at 84 sites on 7 dominant soil groups of the Macquarie region of central-western New South Wales. Over all sites, soil pH (0-10 cm; 1:5 soil: water) ranged from 5.26 to 8.07, medic frequency from 0 to 100% and most probable numbers of R. meliloti from undetectable to 675 000/g soil. There was a highly significant (P<0.001) relationship between soil pH and number of R. meliloti. Above pH 7.0, the mean soil population of R. meliloti was 89000/g; below pH 6.0, it was 37/g. Medics occurred most frequently on the more alkaline soils and with least frequency on the more acid soils, but the relationship between soil pH and medic frequency was weaker than between pH and R. meliloti number. Medics were more tolerant of low soil pH than their rhizobia were; at 2 sites, of pH 5.49 and 5.35, medics occurred at 100% frequency but R. meliloti was undetected. There was an indication of some acidification in these soils over a period of 35 years but this remains to be confirmed.

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Bhagwat, Arvind A., та Donald L. Keister. "Synthesis of β-glucans by Bradyrhizobium japonicum and Rhizobium fredii". Canadian Journal of Microbiology 38, № 6 (1992): 510–14. http://dx.doi.org/10.1139/m92-084.

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Particulate enzyme preparations from Rhizobium and Bradyrhizobium synthesize β-glucans when incubated with uridine diphosphate glucose (UDP-glucose) and a divalent cation. Synthesis of β-1,2-linked glucans in Rhizobium fredii involves the product of the ndvB gene, a 319-kDa membrane protein, which is labeled with [14C]glucose from UDP-[14C]glucose as previously demonstrated in Rhizobium meliloti and Agrobacterium sp. Bradyrhizobium japonicum synthesize β-1,3- and β-1,6-linked glucans of a lower molecular weight than those synthesized by R. meliloti. In comparative experiments, no evidence was found for a protein-bound intermediate in B. japonicum. The ndvB gene of R. fredii was mobilized to B. japonicum and the gene was expressed, as evidenced by appearance of a large membrane protein (ca. 319 kDa) which was labeled with UDP-[14C]glucose in vitro. Key words: soybean, nitrogen fixation, β-glucan, Bradyrhizobium, Rhizobium.

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Lewis, D. M., E. S. P. Bromfield, and L. R. Barran. "Effect of rifampin resistance on nodulating competitiveness of Rhizobium meliloti." Canadian Journal of Microbiology 33, no. 4 (1987): 343–45. http://dx.doi.org/10.1139/m87-059.

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An assessment was made of the effect of high concentration rifampin resistance on the nodulating competitiveness of five strains of Rhizobium meliloti. The results indicate that the acquisition of rifampin resistance by R. meliloti is generally associated with a significant loss of nodulating competitiveness and an altered RNA polymerase insensitive to the action of rifampin. All mutants were similar to their parent strains with respect to growth rates, phage sensitivity patterns, and symbiotic effectiveness. The data suggest that rifampin resistance in R. meliloti is unsuitable as a marker for ecological studies.

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42

SUN, Wenli, Mohamad H. SHAHRAJABIAN, and Qi CHENG. "Archaea, bacteria and termite, nitrogen fixation and sustainable plants production." Notulae Botanicae Horti Agrobotanici Cluj-Napoca 49, no. 2 (2021): 12172. http://dx.doi.org/10.15835/nbha49212172.

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Certain bacteria and archaea are responsible for biological nitrogen fixation. Metabolic pathways usually are common between archaea and bacteria. Diazotrophs are categorized into two main groups namely: root-nodule bacteria and plant growth-promoting rhizobacteria. Diazotrophs include free living bacteria, such as Azospirillum, Cupriavidus, and some sulfate reducing bacteria, and symbiotic diazotrophs such Rhizobium and Frankia. Three types of nitrogenase are iron and molybdenum (Fe/Mo), iron and vanadium (Fe/V) or iron only (Fe). The Mo-nitrogenase have a higher specific activity which is expressed better when Molybdenum is available. The best hosts for Rhizobium legumiosarum are Pisum, Vicia, Lathyrus and Lens; Trifolium for Rhizobium trifolii; Phaseolus vulgaris, Prunus angustifolia for Rhizobium phaseoli; Medicago, Melilotus and Trigonella for Rhizobium meliloti; Lupinus and Ornithopus for Lupini, and Glycine max for Rhizobium japonicum. Termites have significant key role in soil ecology, transporting and mixing soil. Termite gut microbes supply the enzymes required to degrade plant polymers, synthesize amino acids, recycle nitrogenous waste and fix atmospheric nitrogen. The positive effects of Arbuscular mycorrhizal (AM) fungi such as growth promotion, increased root length, leaf area, stem diameter, transplant performance and tolerance to stresses have been reported previously.

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Bae, Y. M., and G. V. Stauffer. "Mutations that affect activity of the Rhizobium meliloti trpE(G) promoter in Rhizobium meliloti and Escherichia coli." Journal of Bacteriology 173, no. 18 (1991): 5831–36. http://dx.doi.org/10.1128/jb.173.18.5831-5836.1991.

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Papa, M. F. Del, M. Pistorio, W. O. Draghi, et al. "Identification and Characterization of a nodH Ortholog from the Alfalfa-Nodulating Or191-Like Rhizobia." Molecular Plant-Microbe Interactions® 20, no. 2 (2007): 138–45. http://dx.doi.org/10.1094/mpmi-20-2-0138.

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Nodulation of Medicago sativa (alfalfa) is known to be restricted to Sinorhizobium meliloti and a few other rhizobia that include the poorly characterized isolates related to Rhizobium sp. strain Or191. Distinctive features of the symbiosis between alfalfa and S. meliloti are the marked specificity from the plant to the bacteria and the strict requirement for the presence of sulfated lipochitooligosac-charides (Nod factors [NFs]) at its reducing end. Here, we present evidence of the presence of a functional nodH-encoded NF sulfotransferase in the Or191-like rhizobia. The nodH gene, present in single copy, maps to a high molecular weight megaplasmid. As in S. meliloti, a nodF homolog was identified immediately upstream of nodH that was transcribed in the opposite direction (local synteny). This novel nodH ortholog was cloned and shown to restore both NF sulfation and the Nif+Fix+ phenotypes when introduced into an S. meliloti nodH mutant. Unexpectedly, however, nodH disruption in the Or191-like bacteria did not abolish their ability to nodulate alfalfa, resulting instead in a severely delayed nodulation. In agreement with evidence from other authors, the nodH sequence analysis strongly supports the idea that the Or191-like rhizobia most likely represent a genetic mosaic resulting from the horizontal transfer of symbiotic genes from a sinorhizobial megaplas-mid to a not yet clearly identified ancestor.

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Broughton, W. J., C. H. Wong, A. Lewin, et al. "Identification of Rhizobium plasmid sequences involved in recognition of Psophocarpus, Vigna, and other legumes." Journal of Cell Biology 102, no. 4 (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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Bergeron, Janique, Carole Beaulieu, Roger C. Levesque, Adam Kondorosi, and Patrice Dion. "Homology between the genes of octopine catabolism of Rhizobium meliloti A3 and corresponding genes from the Ti plasmid." Canadian Journal of Microbiology 39, no. 11 (1993): 1041–50. http://dx.doi.org/10.1139/m93-158.

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The ability to catabolize crown-gall opines is found in Agrobacterium tumefaciens and various types of nonagrobacteria. Among the 75 Rhizobium meliloti strains tested in this work, 6 utilized the opines octopine and octopinic acid as the sole carbon and nitrogen source. From a genomic library of one of these six strains, R. meliloti A3, a clone conferring the octopine catabolism (Occ) phenotype was identified and named pJMA. A different Occ clone, which had been obtained from R. meliloti Rm41, did not hybridize with clone pJMA from strain A3. However, some fragments of clone pJMA hybridized to a 20-kilobase KpnI fragment containing the Ti plasmid genes of octopine catabolism (occ genes) from A. tumefaciens 15955. Shorter probes carrying the octopine permease genes or part of the octopine oxidase and ornithine cyclodeaminase genes from A. tumefaciens also hybridized with pJMA. The R. meliloti DNA carried by pJMA was localized to a megaplasmid of the wild-type strain A3. Thus, it appears possible that genes represented on the Occ clone from strain A3 share a common origin with the corresponding genes from the Ti plasmid.Key words: Rhizobium meliloti, Agrobacterium tumefaciens, octopine catabolism.

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47

Willis, Laura B., та Graham C. Walker. "ThephbC(poly-β-hydroxybutyrate synthase) gene ofRhizobium(Sinorhizobium)melilotiand characterization ofphbCmutants". Canadian Journal of Microbiology 44, № 6 (1998): 554–64. http://dx.doi.org/10.1139/w98-033.

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Defined insertion mutations have been constructed in theRhizobium (Sinorhizobium) meliloti phbC gene, which encodes poly-β-hydroxybutyrate (PHB) synthase. The locus was isolated and subcloned from a genomic library of R. meliloti Rm1021 by complementation of a phbC mutation of Alcaligenes eutrophus. PHB production was detected in wild-type R. meliloti under nutrient-limited conditions but not in rich medium. No PHB production was detected in the R. meliloti phbC mutants. The DNA sequence of the R. meliloti phbC gene was determined. The deduced polypeptide sequence is homologous to previously identified PhbCs from other bacteria. The R. meliloti phbC locus maps to pRmeSU47a, the smaller of the two megaplasmids in this strain.Key words: Rhizobium meliloti, PHB, PHA, poly-β-hydroxybutyrate, phbC.

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Laberge, Serge, Manon Belair, Alain Verreault, Alexander W. Bell, Lucien M. Bordeleau, and Jacques Lapointe. "Purification and partial amino acid sequence of a glutamyl-tRNA synthetase from Rhizobium meliloti." Biochemistry and Cell Biology 67, no. 10 (1989): 674–79. http://dx.doi.org/10.1139/o89-101.

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A glutamyl-tRNA synthetase has been purified to homogeneity from Rhizobium meliloti, using reversed-phase chromatography as the last step. Amino acid sequencing of the amino-terminal region of the enzyme indicates that it contains a single polypeptide, whose molecular weight is about 54 000, as judged by SDS–gel electrophoresis. The primary structures of the amino-terminus region and of an internal peptide obtained by cleavage of the enzyme with CNBr have similarities of 58 and 48% with regions of the glutamyl-tRNA sythetase of Escherichia coli; these are thought to be involved in the binding of ATP and tRNA, respectively. The small amount of glutamyl-tRNA synthetase present in R. meliloti is consistent with the metabolic regulation of the biosynthesis of many aminoacyl-tRNA synthetases.Key words: glutamyl-tRNA synthetase, Rhizobium meliloti, purification, reverse-phase chromatography, amino acid sequence.

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Chan, Y. K., L. R. Barran, and E. S. P. Bromfield. "Denitrification activity of phage types representative of two populations of indigenous Rhizobium meliloti." Canadian Journal of Microbiology 35, no. 7 (1989): 737–40. http://dx.doi.org/10.1139/m89-120.

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Isolates of Rhizobium meliloti from indigenous populations at two sites were previously characterized according to phage sensitivity. Isolates representative of the 55 and 65 phage types comprising these two populations, respectively, were tested for denitrification activity with nitrate or nitrite as substrate. Fifty-seven of 120 isolates were capable of denitrification with activities varying considerably between phage types. Only one isolate was able to denitrify nitrite but not nitrate, indicating the presence of a truncated denitrification pathway. Each of five phage types showed variation in denitrification ability between isolates from different sites, indicating possible adaptation of indigenous R. meliloti to their respective environments. The estimated frequency of occurrence of denitrifiers in the two indigenous populations of R. meliloti (9 and 13%) differed significantly between sites with and without a previous history of Medicago sativa cultivation, respectively.Key words: Rhizobium, denitrification, populations, phage.

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Robledo, Marta, Esther Menéndez, Jose Ignacio Jiménez-Zurdo, et al. "Heterologous Expression of Rhizobial CelC2 Cellulase Impairs Symbiotic Signaling and Nodulation in Medicago truncatula." Molecular Plant-Microbe Interactions® 31, no. 5 (2018): 568–75. http://dx.doi.org/10.1094/mpmi-11-17-0265-r.

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Abstract:

The infection of legume plants by rhizobia is tightly regulated to ensure accurate bacterial penetration, infection, and development of functionally efficient nitrogen-fixing root nodules. Rhizobial Nod factors (NF) have key roles in the elicitation of nodulation signaling. Infection of white clover roots also involves the tightly regulated specific breakdown of the noncrystalline apex of cell walls in growing root hairs, which is mediated by Rhizobium leguminosarum bv. trifolii cellulase CelC2. Here, we have analyzed the impact of this endoglucanase on symbiotic signaling in the model legume Medicago truncatula. Ensifer meliloti constitutively expressing celC gene exhibited delayed nodulation and elicited aberrant ineffective nodules, hampering plant growth in the absence of nitrogen. Cotreatment of roots with NF and CelC2 altered Ca2+ spiking in root hairs and induction of the early nodulin gene ENOD11. Our data suggest that CelC2 alters early signaling between partners in the rhizobia-legume interaction.

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Journal articles on the topic 'Rhizobium meliloti'

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