The Growth Response of Tetrahymena geleii W to Folic Acid and to the Streptococcus lactis R Factor

Abstract

Lederle folic Acid, Parke-Davis Vit. Bc, and Streptococcus lactis R (SLR) factor were tested individually for their growth-promoting activity on T. geleii W. The results were expressed as the no. of organisms per ml. in the 3rd serial transplant after 72 hrs. of incubn. at 25[degree] C. Folic acid crystals and Bc crystals had almost identical activity. Linear responses occurred between concs. of 0.075 and 1.0 millimicro-grams/ml. of medium, whereas concs. lower than 0.075 millimicrograms/ml. were nearly inactive. The activity of SLR factor was very low. Half maximum growth was obtained with a conc. of 360 millimicrograms/ml. and concs. lower than 150 millimicrograms/ml. were inactive. T. geleii W thus appears similar to Lactobacillus casei in its response to the "folic acids" and to SLR factor.