Diazotrophic Mixed Cultures of Azospirillum and Bacillus Species Using Pectin or Rice Plantlets as Substrates

Abstract

In nature Azospirillum and Bacillus are often associated around different roots of plants e. i. rice roots. We have cocultured different strains of these genera on pectin based media and around rice roots using the spermosphere model. On these media cocultures gave significantly higher nitrogenase activity than pure cultures. The nitrogenase activity was mostly produced by Azospirillum. On pectin based media nitrogenase activity occured at the expense of the degradation and fermentation products of pectin. Azospirillum irakense utilized both degradation and fermentation products of pectin, whereas the non pectinolytic strains (A. brasilense, A lipoferum, A. amazonense) utilized only the Bacillus fermentation products of pectin including acetic and succinic acids. In the spermosphere model two polysaccarides could serve as carbon sources for the Bacillus strains, starch of the seed and the root mucigel.KeywordsCarbon SourceNitrogen FixationPure CultureSuccinic AcidRice RootThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.