Euglena gracilis: formation of giant mitochondria.

The addition of antimycin A (0.5 microgram per milliliter) to cultures of a bleached strain of Euglena gracilis in the logarithmic phase of growth on succinate as a carbon source results in (i) an interruption of growth for 24 hours and (ii) an increase in whole-cell respiration and the emergence of a novel succinoxidase activity within 2 to 4 hours. After 3 to 5 hours, the mitochondria enlarge, fuse, and form a sheathlike structure situated close to the periphery of the cell.