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71.
Symbiotic nitrogen fixation of rhizobia and leguminous plants is considered as the most important biologic nitrogen fixation system on earth. Symbiotic nodulafion of gymnosperm Podocarpus macrophyllus and rhizobia has never been reported. In this study, 11 endophytic bacteria strains were isolated from root nodules of P. macrophyllus and its variation P. macrophyllus var. maki. The plant infection tests on these strains indicated that the isolated strains could be nodulated on P. macrophyllus plants, and weak nitrogenase activity of nodules was found in acetylene reduction method. According to the physiological and biochemical characteristics of the 11 strains, GXLO 02 was selected as the representative strain. 16S rDNA full-length sequence analysis of GXLO 02 confirmed that the representative strain GXLO 02 belongs to Rhizobium sp. 相似文献
72.
Thomas-Oates J Bereszczak J Edwards E Gill A Noreen S Zhou JC Chen MZ Miao LH Xie FL Yang JK Zhou Q Yang SS Li XH Wang L Spaink HP Schlaman HR Harteveld M Díaz CL van Brussel AA Camacho M Rodríguez-Navarro DN Santamaría C Temprano F Acebes JM Bellogín RA Buendía-Clavería AM Cubo MT Espuny MR Gil AM Gutiérrez R Hidalgo A López-Baena FJ Madinabeitia N Medina C Ollero FJ Vinardell JM Ruiz-Sainz JE 《Systematic and applied microbiology》2003,26(3):453-465
We have analysed 198 fast-growing soybean-nodulating rhizobial strains from four different regions of China for the following characteristics: generation time; number of plasmids; lipopolysaccharide (LPS), nodulation factors (LCOs) and PCR profiles; acidification of growth medium; capacity to grow at acid, neutral, and alkaline pH; growth on LC medium; growth at 28 and 37 degrees C; melanin production capacity; Congo red absorption and symbiotic characteristics. These unbiased analyses of a total subset of strains isolated from specific soybean-cropping areas (an approach which could be called "strainomics") can be used to answer various biological questions. We illustrate this by a comparison of the molecular characteristics of five strains with interesting symbiotic properties. From this comparison we conclude, for instance, that differences in the efficiency of nitrogen fixation or competitiveness for nodulation of these strains are not apparently related to differences in Nod factor structure. 相似文献
73.
Enzymatic regulation of pyricline nucleotide formation, under symbiotic and non-symbiotic conditions, was analyzed using soybeans (Glycine max L. cv. 'Akisengoku') and rhizobia (Bradyrhizobia japonicum strain A1017), respectively. It was found that levels of pyridine nucleotides in bacteroids in root nodules were different from those in free-living cells of rhizobia. This difference was associated with differences in activities of enzymes involved in the pathway from L-tryptophan to NAD and NADP. That is, these activities were lower in bacteroids than in free-living bacteria and lower in the nodule cytosol than in root extracts. The optimum pH for NAD synthetase in bacteroids, was 9.0. Additionally, the optimum pH for ATP-nicotinamide mononucleotide (NMN) adenyltransferase, final step enzyme in NAD formation, was estimated to be 7.6. In the bacteroid fraction, the K(m) of NAD synthetase (22 microM) was approximately 1/22 of that of ATP-NMN adenyltransferase (482 microM). Vmax values were estimated to be almost in the same order for both NAD synthetase and ATP-NMN adenyltransferase. This is the first report on the formation of pyridine nucleotides originating from L-tryptophan in bacteroids in soybean nodules and free-living bacteria. 相似文献
74.
A subtraction hybridization and PCR amplification procedure was used to isolate two Rhizobium DNA probes which exhibited high degrees of specificity at different levels of taxonomic organization and which could be used as tools for detection of rhizobia in ecological studies. First, a probe was isolated from Rhizobium leguminosarum bv. trifolii strain P3 by removing those Sau3A restriction fragments from a P3 DNA digest which cross hybridized with pooled DNA from seven other strains of the same biovar. The remaining restriction fragments hybridized to DNA from strain P3 but not to DNA from any of the seven other strains. In a similar experiment another DNA probe, specific for the Rhizobium leguminosarum bv. phaseoli and Rhizobium tropici group, was generated by removing sequences from R. leguminosarum bv phaseoli strain Kim 5s with pooled subtracter DNA from eight other Rhizobium, Bradyrhizobium and Agrobacterium species. The same subtraction hybridization technique was also used to isolate symbiotic genes from a Rhizobium species. Results from a 1:1 subtractive DNA hybridization of the broad host range Rhizobium sp NGR234 against highly homologous S. fredii USDA257, combined with those from competitive RNA hybridizations to cosmid digests of the NGR234 symbiotic plasmid, allowed the identification of several NGR234 loci which were flavonoid-inducible and not present in S. fredii USDA257. One of these, ORF-1, was highly homologous to the leucine responsive regulatory protein of E. coli. 相似文献
75.
Symbiotic nitrogen (N2) fixation in legumes may give the host plant a distinct competitive advantage; at the same time it is mainly responsible for introducing N into terrestrial ecosystems which may ultimately benefit all organisms. Depending on environmental conditions, symbiotic N2 fixation may be tuned to the plant's N demand or specifically inhibited (a disadvantage for plants which depend mainly on symbiotic N2 fixation), or even prevented. Thus, the ecological range for symbiotic N2 fixation can be narrower than that of the host plants. A shortage of mineral N is the only case in which adverse environmental conditions clearly favour symbiotic N2 fixation. Variations in number or mass of nodules or nodule morphology are persistent features, that may represent one kind of regulation of N2 fixation. In addition, varying O2 permeability of nodules functions as a rapid and reversible control of N2 fixation which may compensate partially or fully for poor nodulation. The plant's demand for symbiotically fixed N is thought to play a central role in modulating both nodulation and N2 fixation activity; an N feedback mechanism is assumed. The control of symbiotic N2 fixation operates through a series of ecophysiological triggers which are also influenced by complex interactions between legume plants and other organisms in the ecosystem. The proportion of legume biomass and the performance of symbiotic N2 fixation in each individual legume are the main parameters which determine the amount of symbiotically fixed N introduced into a terrestrial ecosystem. The various triggers and N feedback mechanisms from the whole ecosystem to the gene expression level which regulate symbiotic N2 fixation in terrestrial ecosystems are reviewed and discussed in terms of a conceptual model. Although the presented model is based primarily on our knowledge about the physiology of a few leguminous crop species and of ecosystem processes in managed, perennial grassland in temperate climatic conditions, it may stimulate thinking about functional relationships between symbiotic N2 fixation and terrestrial ecosystems at various system levels. 相似文献
76.
Junfang?Zheng Guirong?Liu Wanfu?Zhu Yuguang?Zhou Shulin?LiuEmail author 《中国科学C辑(英文版)》2004,47(3):268-278
Rhizobia, bacteria that fix atmospheric nitrogen, are important agricultural resources. In order to establish the evolutionary
relationships among rhizobia isolated from different geographic regions and different plant hosts for systematic studies,
we evaluated the use of physical structure of the rhizobial genomes as a phylogenetic marker to categorize these bacteria.
In this work, we analyzed the features of genome structures of 64 rhizobial strains. These rhizobial strains were divided
into 21 phylogenetic clusters according to the features of genome structures evaluated by the endonuclease I-Ceul. These clusters
were supported by 16S rRNA comparisons and genomic sequences of four rhizobial strains, but they are largely different from
those based on the current taxonomic scheme (except 16S rRNA). 相似文献
77.
When nitrogen fixing root nodules are formed, Sarothamnus scoparius (broom) is inoculated with its microsymbionts. Nodules studied under light and electron microscopy exhibited typical indeterminate nodule histology with apical, persistent meristem, age gradient of nodule tissues, and open vascular bundles, and also with some particular features such as: the presence of mitotic activity in the infected meristematic cells, lack of infection threads, distribution of bacteria by process of host cell division, and occurrence of a large bacteroid zone only with infected cells. The results of cross-inoculation tests have shown a broad host range for S. scoparius microsymbionts including not only the native host but also species such as: Lupinus luteus, Ornithopus sativa, Lotus corniculatus, Genista tinctoria, Chamaecitisus ratisbonensis, Macroptilium atropurpureum, and Phaseolus vulgaris. In addition, our data established a close symbiotic relationship of S. scoparius nodulators to Bradyrhizobium sp. (Lupinus) by comparison of the partial sequence of nodC gene of the strain CYT7, specific for the broom, to those from Bradyrhizobium sp. (Lupinus) strain D1 and others available in the public databases. 相似文献
78.
79.
S. K. Kavimandan 《Plant and Soil》1985,86(1):141-144
Summary Beneficial effects on yield and N-assimilation in wheat cv. HD2329 due to inoculation with nine strains belonging to six species and cowpea miscellany of genus rhizobium and Azotobacter were observed. Stimulation of soil Azotobacter and Azospirillum in the root region of wheat occurred due to seed inoculation with Rhizobium. 相似文献
80.
Summary Twenty-five slow-growing strains of cowpea rhizobia were examined for growth and nutritional characteristics. Growth and nutritional data of these isolates were surprisingly homogeneous given their proposed genetic diversity. Most strains tested were capable of anaerobic growth in the presence of nitrate and all were found capable of autotrophic growth in a defined atmosphere of CO2 and H2 with oxygen or nitrate as terminal electron acceptors. These isolates grew heterotrophically with various carbohydrates and organic acids. Nitrogen utilization was consistent with that of other slow-growing rhizobia. Medium composition strongly affected the final pH of the culture. Cowpea rhizobia generally did not require vitamins; those requiring vitamins exhibited good growth when biotin was supplemented to the medium. 相似文献