Aerotaxis in Spirillum volutans

Abstract

Spirillum volutans responded aerotactically to self-created oxygen gradients in capillary tubes. Band formation required an oxidizable substrate, inorganic ions, and a chelating agent. The higher the respiratory rate, the faster the band migrated. Random motility occurred in the anaerobic region behind the band. Inhibitor studies indicated the existence of two alternative energy pathways for motility: one involved the oxidation of exogenous substrates while the other allowed energy production in the absence of oxygen uptake and was apparently linked to intracellular poly-β-hydroxybutyrate breakdown. Respiratory inhibitors such as KCN caused decreases in ATP and prevented band formation but allowed motility. 2,4-Dinitrophenol stimulated oxygen uptake but caused decreases in ATP and prevented band formation. Oxidation of substrates without aeration caused decreases in ATP while aeration increased ATP. Aerotactic band formation therefore appeared to result from an avoiding reaction in which cells moved away from the anaerobic environment created by the band, thereby resulting in an increase of cellular ATP. Results with 2,4-dinitrophenol suggested that not only is oxygen uptake required for band formation but also oxidative phosphorylation. Intracellular ATP levels may possibly serve to regulate the aerotactic response.