Previous studies have shown that chemotaxis plays an important role in the colonization of the wheat roots surfaces by Azospirillum brasilense and a chemotaxis operon shown to control motility and chemotaxis in A. brasilense has been isolated. This study looked at the effects of mutations in individual genes coding for chemotaxis proteins from this operon on the ability of the cells to colonize the surface of sterile wheat roots. Using both quantitative and qualitative assays, the study shows differences in the colonization ability of the mutants relative to the wild type: the cheB, cheR, cheBR, and cheOp mutants were significantly impaired in wheat root colonization. Interestingly, the cheA mutant was not affected in its ability to colonize the wheat root surface relative to the wild type. Future studies will look for the factors that compensate for cheA impairment in the rhizosphere.