Physiological characterization of cyanophora paradoxa, a flagellate containing cyanelles in endosymbiosis

Abstract

Culture conditions are described under which Cyanophora paradoxa grows with a generation time of less than two days. The organism is an obligate photoautotrophic flagellate unable to degrade exogenous carbohydrates via respiration. It does not synthesize nitrogenase but can form a hydrogenase with similar properties as in blue-green algae. The photosynthetic O2-evolution proceeds with essentially the same rate as in green or blue-green algae. Besides CO2, p-benzochinon, nitrate and nitrite also stimulate the photosynthetic O2-evolution. Nitrite reduction is strictly lightdependent where the stoicheiometry between nitrite-disappearance and photosynthetic O2-evolution is 1:1.5. It is concluded that the cyanelles supply the eucaryotic host both with carbon and nitrogen compounds. © 1978, Walter de Gruyter. All rights reserved.