Ref ID : 3739
J.G. Peak and M.J. Peak; Heterotrophic (Dark) CO2 Fixation by Euglena gracilis. Possible regulation by tricarboxylic acid cycle intermediates. J.Protozool. 23(1):165-167, 1976
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Heterotrophic (dark) CO2 fixation by Euglena gracilis srain Z varies with phase of batch culture and mode of nutrition. Dark CO2 fixation increased transiently during the growth of cells under photoautotrophic (CO2, light) and heterotrophic (glucose, dark) conditions. Cells grown heterotrophically with acetate or ethanol had no transient increase in fixation. The addition of acetate to a heterotrophically growing culture during the period of increasing dark CO2 fixation resulted in rapid elimination of this fixation. The results suggest that dark CO2 fixation in Euglena functions in anaplerotic feeding of the tricarboxylic acid cycle, drained by biosyntheses during growth. Induction of the glyoxylate cycle by acetate may provide an alternate source of tricarboxylic cycle intermediates, obviating the requirement for dark CO2 fixation as a source of the intermediates.