EFFECT OF OXYGEN ON PHOTO AUTOTROPHIC and HETEROTROPHIC GROWTH OF Chlamydomonas reinhardtii IN AN ANOXIC ATMOSPHERE

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Abstract
Abstract—Photoautotrophic growth ofChlamydomonas reinhardtiiwas shown to be independent of the presence of atmospheric oxygen. Under constant light and photoautotrophic conditions, C.reinhardtiigrew equally well in either air or 367 PPM C02‐in‐He. During 12‐h light‐dark cycles, the cells in air grew substantially faster than those grown in C02‐in‐He, indicating a significant role for 02in dark metabolism. Although cells grown under C02‐in‐He were not supplied any exogenous 02, photosynthetic water splitting resulted in the liberation of 02. The effect of photoevolved 02on the growth ofC. reinhardtiiwas examined (1) by measuring the amount of 02consumed by photosynthesiz‐ing algae, (2) by growing the algae heterotrophically on acetate in the dark and supplied with 02generated by photoautotrophically grown cells, and (3) by determining the minimum level of 02needed to stimulate C02evolution from cells suspended in minimal medium supplemented with acetate. The results from these investigations indicated that exogenous 02was not required for photoautotrophic growth byC. reinhardtiiand that this alga grew in an anoxic environment if supplied with C02and light.