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. 1986 Sep;52(3):520–526. doi: 10.1128/aem.52.3.520-526.1986

Close Association of Azospirillum and Diazotrophic Rods with Different Root Zones of Kallar Grass

Barbara Reinhold 1,*, Thomas Hurek 1, Ernst-Georg Niemann 1, Istvan Fendrik 1
PMCID: PMC203566  PMID: 16347149

Abstract

The populations of diazotrophic and nondiazotrophic bacteria were estimated in the endorhizosphere and on the rhizoplane of Kallar grass (Leptochloa fusca) and in nonrhizosphere soil. Microaerophilic diazotrophs were counted by the most-probable-number method, using two semisolid malate media, one of them adapted to the saline-sodic Kallar grass soil. Plate counts of aerobic heterotrophic bacteria were done on nutrient agar. The dominating N2-fixing bacteria were differentiated by morphological, serological, and physiological criteria. Isolates, which could not be assigned to a known species, were shown to fix nitrogen unequivocally by 15N2 incorporation. On the rhizoplane we found 2.0 × 107 diazotrophs per g (dry weight) of root, which consisted in equal numbers of Azospirillum lipoferum and Azospirillum-like bacteria showing characteristics different from those of known Azospirillum species. Surface sterilization by NaOCI treatment effectively reduced the rhizoplane population, so that bacteria released by homogenization of roots could be regarded as endorhizosphere bacteria. Azospirillum spp. were not detected in the endorhizosphere, but diazotrophic, motile, straight rods producing a yellow pigment occurred with 7.3 × 107 cells per g (dry weight) of root in the root interior. In nonrhizosphere soil we found 3.1 × 104 nitrogen-fixing bacteria per g. Diazotrophs were preferentially enriched in the Kallar grass rhizosphere. In nonrhizosphere soil they made up 0.2% of the total aerobic heterotrophic microflora, on the rhizoplane they made up 7.1%, and in the endorhizosphere they made up 85%. Owing to high numbers in and on roots and their preferential enrichment, we concluded that diazotrophs are in close association with Kallar grass. They formed entirely different populations on the rhizoplane and in the endorhizosphere.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Barraquio W. L., Ladha J. K., Watanabe I. Isolation and identification of N2-fixing Pseudomonas associated with wetland rice. Can J Microbiol. 1983 Aug;29(8):867–873. doi: 10.1139/m83-141. [DOI] [PubMed] [Google Scholar]
  2. Cáceres E. A. Improved Medium for Isolation of Azospirillum spp. Appl Environ Microbiol. 1982 Oct;44(4):990–991. doi: 10.1128/aem.44.4.990-991.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Döbereiner J., Baldani V. L. Selective infection of maize roots by streptomycin-resistant Azospirillum lipoferum and other bacteria. Can J Microbiol. 1979 Nov;25(11):1264–1269. doi: 10.1139/m79-199. [DOI] [PubMed] [Google Scholar]
  4. Haahtela K., Helander I., Nurmiaho-Lassila E. L., Sundman V. Morphological and physiological characteristics and lipopolysaccharide composition of N2-fixing (C2H2-reducing) root-associated Pseudomonas sp. Can J Microbiol. 1983 Aug;29(8):874–880. doi: 10.1139/m83-142. [DOI] [PubMed] [Google Scholar]
  5. Haahtela K., Wartiovaara T., Sundman V., Skujiņs J. Root-associated n(2) fixation (acetylene reduction) by enterobacteriaceae and azospirillum strains in cold-climate spodosols. Appl Environ Microbiol. 1981 Jan;41(1):203–206. doi: 10.1128/aem.41.1.203-206.1981. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. MUELLER-BEISSENHIRTZ W., KELLER H. ZUR BESTIMMUNG DES BLUTAMMONIAKS. Klin Wochenschr. 1965 Jan 1;43:43–49. doi: 10.1007/BF01485589. [DOI] [PubMed] [Google Scholar]
  7. McClung C. R., van Berkum P., Davis R. E., Sloger C. Enumeration and Localization of N(2)-Fixing Bacteria Associated with Roots of Spartina alterniflora Loisel. Appl Environ Microbiol. 1983 Jun;45(6):1914–1920. doi: 10.1128/aem.45.6.1914-1920.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Reinhold B., Hurek T., Fendrik I. Strain-specific chemotaxis of Azospirillum spp. J Bacteriol. 1985 Apr;162(1):190–195. doi: 10.1128/jb.162.1.190-195.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Rennie R. J. Dinitrogen-fixing bacteria: computer-assisted identification of soil isolates. Can J Microbiol. 1980 Nov;26(11):1275–1283. doi: 10.1139/m80-213. [DOI] [PubMed] [Google Scholar]
  10. Watanabe I., Barraquio W. L., De Guzman M. R., Cabrera D. A. Nitrogen-fixing (acetylene redution) activity and population of aerobic heterotrophic nitrogen-fixing bacteria associated with wetland rice. Appl Environ Microbiol. 1979 May;37(5):813–819. doi: 10.1128/aem.37.5.813-819.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. van Berkum P., Bohlool B. B. Evaluation of nitrogen fixation by bacteria in association with roots of tropical grasses. Microbiol Rev. 1980 Sep;44(3):491–517. doi: 10.1128/mr.44.3.491-517.1980. [DOI] [PMC free article] [PubMed] [Google Scholar]

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