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  • Enterobacter agglomerans  (1)
  • Klebsiella pneumoniae  (1)
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  • 1
    ISSN: 1432-072X
    Keywords: Enterobacter agglomerans ; Klebsiella ; nif genes ; Diazotrophic ; Plasmids ; Root-associated ; Nitrogenase physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our previous work showed that strains of dinitrogen fixing enterobacter and Klebsiella were found associated with the roots of uncultivated grasses in Finland more commonly than other species of diazotrophic bacteria. In this paper we compare E. agglomerans strains to K. pneumoniae and K. terrigena strains, and show that the E. agglomerans strains fall into two biogroups. The groups differ not only in the utilization of different carbon sources and other physiological characteristics such as the production of indole, but also in the physiology and genetics of nitrogenase activity. Biotype 1 (isolated from Achillea millefolium, Calamagrostis arundinacea, and Phleum pratense) showed active nitrogenase in atmospheric oxygen, whereas biotype 2 (from Phalaris arundinacea) resembled K. pneumoniae in that it was active at reduced oxygen pressure (pO2〈-0.002) only. DNA of all strains showed positive hybridization with K. pneumoniae nifHDK genes (pSA30) but differed in the location of the genes. Biotype 1 strains of E. agglomerans carried nifHDK genes on large (105–125 Mdal) plasmids, whereas no plasmid was detected in biotype 2 or in the K. pneumoniae strains isolated from Agrostis stolonifera and Poa pratensis and K. terrigena strain isolated from Carex pallescens. The one K. terrigena strain (isolated from Ph. arundinacea) that was found to contain an indigenous plasmid (80 Mdal) did not carry nifHDK genes on this plasmid.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: Blue grass ; Klebsiella pneumoniae ; Poa pratensis ; Triticum aestivum ; Nitrogen fixation ; Nitrogen nutrition ; 15N isotope dilution ; Spring wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The technique of15N isotope dilution was used to verify that nitrogen was fixed and transferred to the plant byKlebsiella pneumoniae strain Pp in association withPoa pratensis orTriticum aestivum. Surface sterilized, sprouting seeds were inoculated withK. pneumoniae and grown in sand in modified Leonard jars. Potassium nitrate enriched with15N was used to provide N concentrations ranging from 10–40 mg Nl−1 nutrient solution. After 10–18 weeks the shoots and roots were analyzed separately for dry matter, N content, total N, and atom %15N excess. The acetylene reduction technique was used to test for the presence of N2-fixing organisms on the roots. The data from15N isotope dilution demonstrated that up to 33.8% of N in the shoots ofP. pratensis and 15.9% in those ofT. aestivum were derived from associative N2 fixation byK. pneumoniae. In most experiments the dry matter yield, N content, and total N yield of the shoots ofP. pratensis were increased byK. pneumoniae inoculation, whereas inoculation had no significant effect on the dry matter yield, N content or total N of the shoots ofT. aestivum.
    Type of Medium: Electronic Resource
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