Cytochrome c oxidase as the receptor molecule for chemoaccumulation (chemotaxis) of Euglena toward oxygen

Chemoaccumulation of Euglena gracilis toward oxygen was selectively inhibited, without concomitant effects on cell motility, by cyanide (10(-6) to 10(-4) molar) and carbon monoxide (5 x 10(-5) to 5 x 10(-4) molar). Above these concentrations, motility of the cell was imparied and the chemosensory response was inhibited. Azide did not affect chemoaccumulation even at 5 x 10(-3) molar. It is concluded that cytochrome a3 serves as the chemoreceptor molecule for oxygen-mediated behavioral responses in Euglena.