Microbiological Assays for Vitamin B12: A Cyanide Enhancement Effect

Shorb (1) showed that La&bacillus luctis Dorner requires an unknown factor for growth, and designated it as LLD.This factor was shown later to be identical with crystalline vitamin Blz (2).Reducing agents could replace the vitamin B 12 requirements of this organism (3).Although a suitable synthetic medium was devised which eliminated the need for the tomato juice eluate previously employed and which minimized the variable effects brought about by reducing agents (4), Shorb and Briggs showed that dissociation of the organism often occurred, resulting in strains not requiring vitamin BU (5).Skeggs et al. ( 6) suggested the use of Lactobacillus Zeichmannii ATCC 4797 as a more stable assay organism.Hoffmann et al. ( 7) employed L.