Response to and Assay of Vitamin B 12 by a Mutant of Escherichia coli . ∗

Abstract

Summary

A mutant organism, Escherichia coli 113-3, which responds to vit. B₁₂ or methionine in a mineral salts-citrate-glucose medium, was adopted successfully for the assay of vit. B₁₂. The effects of the degree of aero-biosis, and of potassium cyanide and two reducing agents, upon the response of this bacterium to vit. B₁₂ and B_12a are described.