RESPIRATION OF EUGLENA-GRACILIS GROWN UNDER CONDITIONS OF VITAMIN-B12-SUFFICIENCY, VITAMIN-B12-DEFICIENCY, AND VITAMIN-B12-REPLENISHMENT

Respiration rates were measured in vitamin B-12-sufficient, -deficient and -replenished cells of Euglena gracilis. With increasing vitamin B-12 deficiency the respiratory rate increases to a maximum value 2-fold higher than that of exponentially-growing vitamin B-12-sufficient cells. Respiratory rates decline sharply in both stationary-phase vitamin-sufficient and advanced vitamin-deficient cells. as a consequence of nutrient depletion from the growth medium. There was no net difference in overall O2 uptake in vitamin-deficient and -replenished cells. The data indicate that vitamin B-12 deficiency does not deleteriously affect respiration in Euglena.