Chemotaxis ofAzospirillum brasilense towards compounds typical of plant root exudates

Nitrogen-fixingAzospirillum brasilense exhibits positive chemotaxis towards a large number of organic compounds (amino acids, saccharides, organic acids) typical for plant root exudates. The most effective attractants were malate, succinate, fructose and other compounds which serve as substrates forA. brasilense. Chemotactic response towards the majority of compounds was inducible, but in case of malate and succinate it was constitutive. Tactic response during the nitrogen-fixing process was essentially the same as in the presence of fixed nitrogen in the medium. Among organic compounds tested no repellents were found.