Aerotaxis and chemotaxis of Azospirillum brasilense: A note

Azospirillum brasilense was attracted to capillaries containing either phosphate buffer, distilled water, or saline. The number of bacteria in these capillaries was 3-4×10⁴, after 1 h of incubation. In the presence of phosphate buffer + attractants, the number of cells accumulated in the capillary increased only to 5×10⁴-1.1×10⁵ cells. It was not possible, therefore, to measure chemotaxis in A. brasilense as distinct from aerotaxis by the capillary method. Chemotaxis was observed in semi-solid agar plates and was determined by a growth band oriented towards the attractant. Positive chemotactic response was obtained with peptone, tryptone, yeast extract, amino acids, organic acids, arabinose and galactose.