Abstract: | SYNOPSIS Heterotrophic (dark) CO2 fixation by Euglena gracilis strain Z varies with phase of batch culture growth and mode of nutrition. Increases in the fixation during growth cycles correlate closely with the depletion of exogenous NH4* from the medium during growth. It is demonstrated that exogenous NH4+ regulates a component of heterotrophic CO2 fixation and that another component is independent of NH4+. This is true for cells grown heterotrophically (glucose, dark), autotrophically (CO2, light) and for a permanently bleached strain (E. gracilis SB3). Some kinetics of the NH4+ regulation are presented. |