Investigations into the Euglena Gracilis Method for Quantitative Assay of Vitamin B₁₂

Abstract

Summary. Using Ross's modification of Hutner's method for quantitative determination of vitamin B 12 with Euglena gravities var. bacillaris , experiments were carried out which showed that the supernatant from a centrifuged vigorously growing Euglena culture contains a thermolabile factor, which has a growth‐inhibiting effect on Euglena cells when they are transferred to a freshly prepared medium containing vitamin B 12 . Density and uniformity of growth in the tubes inoculated are increased by washing and diluting the Euglena culture used for inoculation. The sensitivity and the accuracy of the method are thereby increased.