ON THE NATURE OF THE VITAMIN B12 REQUIREMENT IN SOIL BACTERIA ISOLATED BY LOCHHEAD AND HIS CO-WORKERS

Abstract

Of 19 isolates of vitamin-B12-requiring soil bacteria, representing 10 distinct types, only one, "No. 12," responded to Factor A or B or pseudovitamin B12 Growth of several of the organisms was retarded by relatively high concentrations of pseudovitamin B12. Vitamin B12III was active for all but generally less so than cyanocobalamin. The potential usefulness of these organisms as research tools is discussed, together with the ecological implications of the discovery by Lochhead and co-workers of the abundance of vitamin-B12-requiring bacteria in the soil.