Related Experiment Video
Updated: Aug 8, 2026

A Method for Adapting Euglena gracilis to Cassava-Based Substrates for Heterotrophic Cultivation
Published on: June 12, 2026
Photosynthesis of Euglena gracilis under Cobalamin-Sufficient and -Limited Growing Conditions
Y Isegawa1, Y Nakano, S Kitaoka
1Department of Hygiene, Kobe University School of Medicine, Chuo-ku, Kobe 650, Japan.
Abstract:
Cobalamin is essential for growth of Euglena gracilis and photosynthesis. Methylcobalamin in Euglena chloroplasts (Y Isegawa, Y Nakano, S Kitaoka, 1984 Plant Physiol 76: 814-818) functions as a coenzyme of methionine synthetase. The requirement of cobalamin for photosynthesis appeared remarkably high in Euglena grown under the dark-precultured condition. The required amount of cobalamin for normal photosynthetic activity was 7.4 x 10(-11) molar, while 7.4 x 10(-10) molar cobalamin was required for normal growth. The lowered photosynthetic activity in cobalamin-limited cells was restored 20 hours after feeding cyanocobalamin or methionine to cobalamin-limited cells. Lowering of photosynthetic activity was due to loss of photosystem I activity. This photosynthetic activity was recovered after supplementation by methionine or cobalamin. The results suggest that methionine serves for the stabilization of photosystem I. This paper is the first report of the physiological function of cobalamin in chloroplasts of photosynthetic eukaryotes.
Related Concept Videos
Anoxygenic Photosynthesis
The Calvin Benson Cycle
Oxygenic Photosynthesis
Photosystem II
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
What is Photosynthesis?
Anatomy of Chloroplasts

