抄録
A difficulty to obtain a clear and sharply defined growth zone of the test organism has been reported in the cup-plate method for bioassay of certain vitamins. Thus, the application of resazurin, an oxido-reducing dye, used as an indicator, to the cup-plate procedure was attempted to increase the visibility of the growth zones of Lactobacillus fermenti on the assay plate for thiamine. Under the aerobic condition the dye was used after the conventional plate procedure and it was reduced to colourless substance within several minutes by the organism. There was a better contrast between the growth zones and the dark violet zone of back ground. The growth zones observed in this manner coincided accurately with the original zones and it was found from the statistical analysis of the results for thiamine that resazurin treatment scarcely affected the precision of the plate method.
