Abnormal Morphology of a Bacterium Resulting From Vitamin B12 Deficiency

Studies of a vitamin B12-requiring bacterium of the genus Arthrobacter showed that with suboptimal concentrations of the vitamin growth in liquid medium was flocculent whereas with adequate amounts of B12 cultures were uniformly turbid. Flocculation, which was progressively more pronounced with decreasing vitamin supply, was associated with abnormal cell morphology. Cells were noticeably swollen and elongated, irregularly bent, and showed rudimentary branching. The critical concentration of vitamin B12 below which morphological changes began to occur was approximately 0.3 mμgm. per ml.