The use of depleted cells as inocula in vitamin assays

Abstract

Preparation of assay inocula in such a way that the cells contain a reduced level of the vitamin to be assayed gives low background growth in plates, and the greater contrast enhances zone definition. Steps required to be taken to find the optimum conditions for preparation of inocula are described. The assays of nicotinamide, pantothenic acid, folic acid and vitamin B₆ can be improved in this way.