Accumulation of Co⁵⁸‐Vitamin B₁₂ by <i>Euglena gracilis</i>*

Abstract

Some conditions for optimum accumulation of vitamin B 12 by resting Euglena gracilis cells were studied. Accumulation involves intracellular binding, as confirmed by disruption of the cells and differential centrifugation. At least 70% of the intracellular B 12 was attached to sedimentable particles, apparently to the mitochondrial and cell wall‐membrane fractions. The latter contains a heat‐labile substance which rapidly binds B 12 .