The Effects of Common Salts on the Euglena gracilis Bioassay of Vitamin B 12 1

Abstract

Summary

Euglena gracilis cultures were grown in standard media with the addition of varying concentrations of NaCl and NaH₂PO₄. The growth response was greatest between 1.7 and 106.3 mM NaCl and 2.0 and 62.5 mM NaH₂PO₄. The growth potentiation was only observed in the presence of cyanocobalamin. Concentrations of and greater than 212.5 mM NaCl and 125.0 mM NaH₂PO₄ inhibited or eliminated growth of the test organism. Since it often is desirable to determine the vitamin B-12 level by E. gracilis bioassay of chromatographed serum fractions, the assayed B-12 levels may be either erroneously high or low because of the ions present in the eluting buffers. It appeared that addition of ions to the standards of growth in amounts equal to the concentration in the unknown corrected for the effect of the ions.