Current Microbiology

, Volume 53, Issue 1, pp 43–47 | Cite as

Relationship Between In Vitro Enhanced Nitrogenase Activity of an Azospirillum brasilense Sp7 Mutant and Its Growth-Promoting Activities In Situ

  • Samanta Bolzan de Campos
  • Luiz Fernando Wurdig Roesch
  • Maria Helena Bodanese Zanettini
  • Luciane Maria Pereira PassagliaEmail author


In this work, we further analyzed an Azospirillum brasilense Sp7 mutant (Sp7::Tn5-33) showing a pleiotrophic phenotype due to a Tn5 insertion into an open reading frame of 840 bp (orf280). The deduced amino acid sequence of this region has high similarity to a family of universal stress proteins. Because the most interesting property exhibited by the Sp7::Tn5-33 mutant was an enhanced in vitro nitrogen fixation activity, we addressed the question of whether it could benefit the host plant. We found that the increased nitrogenase activity at the free-living state of the mutant bacterium was correlated with an increased production of the nitrogenase reductase protein (NifH), in amounts approximately 1.5 times higher than the wild type. The mutant strain exhibited the same level of auxin production and the same colonization pattern of wheat roots as the wild type. We also observed that Sp7::Tn5-33 increased the total plant dry weight, although the N content did not differ significantly between wheat plants inoculated with mutant or wild-type strains.


Indole Acetic Acid Azospirillum Azospirillum Brasilense Auxin Production Nitrogen Fixation Activity 
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We thank E. Souza for providing the opportunity for S.B.C. to develop part of the immunoblotting experiments in his laboratory and for the donation of anti-dinitrogenase reductase antibody. S.B.C. and L.F.W.R. are in receipt of scholarships from the Brazilian National Research Council (CNPq, Ministry of Science and Technology, Brazil) or Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Ministry of Education, Brazil). We thank G. Pasquali for critically reading the manuscript.

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Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Samanta Bolzan de Campos
    • 1
  • Luiz Fernando Wurdig Roesch
    • 2
  • Maria Helena Bodanese Zanettini
    • 1
  • Luciane Maria Pereira Passaglia
    • 1
    Email author
  1. 1.Departamento de GenéticaInstituto de Biociências, Universidade Federal do Rio Grande do SulPorto AlegreBrazil
  2. 2.Faculdade de AgronomiaUniversidade Federal do Rio Grande do SulPorto AlegreBrazil

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