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  • 1
    Electronic Resource
    Electronic Resource
    The unique root-nodule symbiosis between Rhizobium and the aquatic legume, Neptunia natans (L. f.) Druce (1995)
    Springer
    Planta 196 (1995), S. 311-320 
    Details
    ISSN: 1432-2048
    Keywords: Infection ; Neptunia (root nodules) ; Nitrogen fixation ; Nodulation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the development of the aquatic N2-fixing symbiosis between Rhizobium sp. (itNeptunia) and roots of Neptunia natans L. f. (Druce) (previously N. oleracea Lour.) under natural and laboratory conditions. When grown in its native marsh habitat, this unusual aquatic legume does not develop root hairs, the primary sites of rhizobial infection for most temperate legumes. Under natural conditions, the aquatic plant floats and develops nitrogen-fixing nodules at emergence of lateral roots on the primary root and on adventitious roots at stem nodes, but not from the stem itself. Cytological studies using various microscopies revealed that the mode of root infection involved an intercellular route of entry followed by an intracellular route of dissemination within nodule cells. After colonizing the root surface, the bacteria entered the primary root cortex through natural wounds caused by splitting of the epidermis and emergence of young lateral roots, and then stimulated early development of nodules at the base of such roots. The bacteria entered the nodule through pockets between separated host cells, then spread deeper in the nodule through a narrower intercellular route, and eventually evoked the formation of infection threads that penetrated host cells and spread throughout the nodule tissue. Bacteria were released from infection droplets at unwalled ends of infection threads, became enveloped by peribacteroid membranes, and transformed into enlarged bacteroids within symbiosomes. In older nodules, the bacteria within symbiosomes were embedded in an unusual, extensive fibrillar matrix. Cross-inoculation tests of 18 isolates of rhizobia from nodules of N. natans revealed a host specificity enabling effective nodulation of this aquatic legume, with lesser affinity for Medicago sativa and Ornithopus sp., and an inability to nodulate several other crop legume species. Acetylene reduction (N2 fixation) activity was detected in nodules of N. natans growing in aquatic habitats under natural conditions in Southern India. These studies indicate that a specific group of Rhizobium sp. (Neptunia) occupies a unique ecological niche in aquatic environments by entering into a N2-fixing root-nodule symbiosis with Neptunia natans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201390
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  • 2
    Electronic Resource
    Electronic Resource
    Subnanomolar concentrations of membrane chitolipooligosaccharides from Rhizobium leguminosarum biovar trifolii are fully capable of eliciting symbiosis-related responses on white clover (1996)
    Springer
    Plant and soil 186 (1996), S. 93-98 
    Details
    ISSN: 1573-5036
    Keywords: chitolipooligosaccharide ; Rhizobium-Trifolium repens symbiosis ; root hair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Axenic seedling bioassays were performed on white clover, vetch, and alfalfa to assess the variety and dose responses of biological activities exhibited by membrane chitolipooligosaccharides (CLOSs) from wild type Rhizobium leguminosarum bv. trifolii ANU843. Subnanomolar concentrations of CLOSs induced deformation of root hairs (Had) and increased the number of foci of cortical cell divisions (Ccd) in white clover, some of which developed into nodule meristems. In contrast, ANU843 CLOSs were unable to induce Had in alfalfa and required a 104-fold higher threshold concentration to induce this response in vetch. Also, ANU843 CLOSs were not mitogenic on either of these non-host legumes. In addition, CLOS action also increased chitinase activity in white clover root exudate. Thus, the membrane CLOSs from wild type R. leguminosarum bv. trifolii are fully capable of eliciting various symbiosis-related responses in white clover in the same concentration range as extracellular CLOSs of other rhizobia on their respective legume hosts. These results and our earlier studies indicate that membrane CLOSs represent one of many different classes of bioactive metabolites made by R. leguminosarum bv. trifolii which elicit more intense symbiosis-related responses in white clover than in other legumes. Therefore, CLOSs evidently play an important role in symbiotic development, but they may not be the sole determinant of host-range in the Rhizobium-clover symbiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035061
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid Identification of Clavibacter michiganensis Subspecies Sepedonicus based on the Stable Low Molecular Weight RNA (LMW RNA) Profiles (2000)
    Springer
    European journal of plant pathology 106 (2000), S. 789-793 
    Details
    ISSN: 1573-8469
    Keywords: Clavibacter ; subsp. sepedonicus ; potatoes ; disease ; RNA ; electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Clavibacter michiganensis subsp. sepedonicus causes potato ring rot disease. The identification process for this bacterium is complex and long. This work demonstrates that the stable low-molecular-weight (LMW) RNA profiles allow their rapid identification. Staircase electrophoresis in polyacrylamide gels was used to analyze the LMW RNA profiles of 54 strains of C. michiganensis subsp. sepedonicus from different geographic origins. The profiles of several strains of other subspecies of C. michiganensis and other pathogens of potatoes were also analyzed. All the strains of C. michiganensis subsp. sepedonicus had the same LMW RNA profile. They had a band in class 2 of tRNA that was absent in the other subspecies of the species C. michiganensis. Also, the LMW RNA of C. michiganensis subsp. sepedonicus was different with respect to the LMW RNA profiles of other pathogens of potato. The results indicate the possible utilization of LMW RNA profiles in identification of the bacteria causing potato ring rot disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026539507031
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  • 4
    Electronic Resource
    Electronic Resource
    Enhancement of resolution of low molecular weight RNA profiles by staircase electrophoresis (1997)
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 1909-1911 
    Details
    ISSN: 0173-0835
    Keywords: Electrophoresis ; RNA ; Low molecular weight RNA ; Microbial taxonomy ; Microbial ecology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Stable low molecular weight (LMW) RNA comprises molecules used in the taxonomy of microorganisms and in studies on the microbial diversity of populations. However, the use of electrophoretic techniques has been hampered due to the low resolution obtained with techniques used for the separation of this kind of molecule. In this work we develop an electrophoretic method (staircase electrophoresis) that increases the resolution of the technique. This improvement in the resolution adequately resolves the three zones that integrate the profiles of LMW RNA: ribosomic 5S RNA (5S rRNA), class 2 transfer RNA (tRNA), and class 1 transfer RNA, allowing the technique to be applied to taxonomic studies (diagnostic, the identification of the individuals), phylogenetic studies and studies on naturally occurring microbial populations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150181103
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