Serological relationships of azospirilla revealed by their motility patterns in the presence of antibodies to lipopolysaccharides

Motility of the serologically different Azospirillum brasilense strains Sp245 (serogroup I) and Sp7 (serogroup II) was studied in the presence of antibodies to their lipopolysaccharides (LPS). A procedure was proposed in order to determine the motility patterns indicating the specificity of the interaction between the anti-LPS antibodies and bacteria. Analysis of the effect of such antibodies on motility of 25 strains (A. brasilense, A. lipoferum, A. irakense, and Azospirillum sp.) revealed bacteria exhibiting antigenic cross reactions with A. brasilense Sp7 or Sp245. The effect of anti-LPS antibodies on motility of azospirilla was in agreement with the results of immune agglutination analysis of bacterial cells and of immunodiffusion analysis of the LPS preparations. According to our results, strains Azospirillum sp. SR81 and A. brasilense SR14 should be included into serogroups I and II, respectively.