The Utilization of Acetate by Wild-type and Mutant Chlamydomonas dysosmos

Abstract

These studies were undertaken in an attempt to elucidate underlying causes of obligate auto-trophy. Wild-type C. dysosmos is capable of normal photo-synthetic growth, and of heterotrophic growth in darkness on acetate, pyruvate or lactate. An UV-induced mutant was isolated which behaved like an obligate photo-autotroph. In the presence of 2:4-dinitrophenol (5 x 10-5 M) or NaN3 (1 x 10-5 m), the wild-type similarly behaved in growth experiments like an obligate photo-autotroph. Mutant cells oxidized all added acetate to CO2. Wild-type cells oxidized a portion of the substrate, and utilized some of the energy so released for the assimilation of the remainder. There are indications that in the wild-type the assimilation of acetate commences only after a period of acetate oxidation. The mutant is believed to be impaired in its ability to effect oxidative assimilation.