The activity of Lactobacillus casei factor, folic acid, and vitamin Bc for Streptococcus faecalis and Lactobacillus casei.

It has been established that the terms vitamin M, vitamin B,, norit eluate factor, Lactobacillus casei factor, factor U, folic acid, and factor SLR all refer to a group of compounds (or a compound) with similar characteristics and similar biological activities. Of these factors seven have been reported in purified form: folic acid (isolated from spinach) (l), three L. casei factors (one from liver, one from yeast, and one from a fermentation residue) (2, 3), synthetic liver L. casei factor (4), vitamin B, (from liver or yeast) (5), and factor SLR (6). Pure folic acid was originally (1) assigned a potency of 40,000 (i.e. the pure compound was said to be 40,000 times as active as Wilson’s liver fraction B). In the work reported from this laboratory (7) on the excretion of folic acid in sweat and urine, a folic acid concentrate furnished by Dr. R. J. Williams was used as standard, and the results were reported in terms of 40,000 potency. However, other active compounds have become available in pure form and Mitchell, Snell, and Williams (8) have reported a folic acid concentrate with a potency of 137,000. Therefore, in order to obtain a means of comparing data reported on the basis of 40,000 potency folic acid with dat.a based on pure compounds as standards, the relative activities of vitamin B,, folic acid concentrate, synthetic Lactobacillus casei factor, and fermentation L. casei factor for Streptococcus faecalis and L. casei were determined. The activities of several of these materials in terms of requirements for half maximum growth have been reviewed by Luckey, Teply, and Elvehjem (9) and by Peterson and Peterson (10).