Studies on the Nutrition of Colorless Euglenoid Flagellates. II. Growth of Astasia in an Inorganic Medium

Abstract

Astasia sp., in pure culture, was grown in darkness for 24 serial transfers, covering a period of over 19 months, in a purely inorganic medium containing (NH4)2HPO4, MgSO4, KH2PO4, KCl and FeCl3. Growth curves show that growth continued for approx. 18 days after organisms were introduced into fresh medium, and not during the first few days only as might be expected should the observed growth be due to traces of organic substances in the medium. It was also shown that growth in the inorganic medium was not due to traces of organic substances which may have gained access to the medium during autoclaving from cotton plugs used to stopper the culture vessels, as impurities in the water and salts employed, or from the air. Better growth was observed in cultures exposed to 5% CO2 in air than in cultures exposed to atmospheric air. All these results indicate that Astasia sp. is capable of chemoautotrophic nutrition; that it can use CO2 as the sole C source, utilize inorganic X, and obtain the necessary energy for metabolic processes by the oxidation of some inorganic constituent of the medium.