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Light microscopical visualization of diazotrophs on and in roots by immunogold-silver staining

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The protein A-gold technique with subsequent silver amplification was used to visualize specific bacteria in plant roots by light microscopy. Polyclonal antibodies against diazotrophic rods were labelled with staphylococcal protein A-gold on semithin sections of resin-embedded samples. The visibility of colloidal-gold-labelled structures was enhanced by additional silver amplification. Results showed that embedding the bacteria in resin LR White soft grade preserved bacterial structure and avoided loss of antigenicity. Application of this method avoided problems with autofluorescence of plant material and eliminated and the requirement for a fluorescence microscope, and gave a specific staining of the bacteria, which remained well fixed. Diazotrophic rods occurring in high numbers inside the roots of Kallar grass plants at a natural site in Pakistan were able to colonize the aerenchyma of Kallar grass roots grown in gnotobiotic culture.

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Correspondence to B. Reinhold.

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Reinhold, B., Hurek, T. Light microscopical visualization of diazotrophs on and in roots by immunogold-silver staining. Biol Fert Soils 6, 298–301 (1988).

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Key words

  • Protein A-gold
  • Nitrogen-fixing bacteria
  • Kallar grass
  • Root interior
  • Colonization
  • Leptochloa fusea