THIAMINE AND TETRAHYMENA

¹ Arnold Biological Laboratory, Brown University, Providence, Rhode Island

1. Tetrahymena geleii will grow in serial transplants in completely dethiaminized filtered and diluted casein solution plus salts and riboflavin. Added thiamine has no effect upon the population.

2. Growth rate, population at the end of exponential growth and maximum yield are greatly increased when dethiaminized alfalfa extract is added.

3. No growth occurs in completely hydrolysed casein even with added thiamine.

4. Good growth occurs in casein hydrolysate plus dethiaminized alfalfa extract. Heat and alkali treatment of the hydrolysate or the addition of thiamine have no significant effect.

5. Whole gelatin and dethiaminized whole gelatin support transplantable growth. The addition of thiamine has no effect during logarithmic growth but causes an increase in maximum yield.

6. The addition of dethiaminized alfalfa extract to gelatin and to dethiaminized gelatin increases significantly the reproductive rate, population at the end of logarithmic growth and the maximum yield.

7. Gelatin hydrolysate and dethiaminized gelatin hydrolysate support growth only when alfalfa extract is added. The addition of thiamine has no significant effect.

8. Ciliates growing in gelatin or heated gelatin alone become extremely small and sluggish after about the eighth day. They remain viable up to 30 days, however. The addition of thiamine causes the ciliates to become very large in old cultures. The addition of alfalfa extract produces ciliates intermediate in size.

9. The conclusion is reached that casein and gelatin possesses small amounts of "factor S" which makes it possible for Tetrahymena geleii to synthesize thiamine. "Factor S" from alfalfa extract, together with "factors I and II" (Dewey, 1944) added to casein or gelatin, produce rapid and heavy growth. Thiamine is not a "growth factor" for T. geleii (strain W).