GROWTH STUDIES ON CILIATES

VII. COMPARATIVE GROWTH CHARACTERISTICS OF FOUR SPECIES OF STERILE CILIATES

¹ Arnold Biological Laboratory, Brown University

1. The growth characteristics of four species of holotrichous ciliates (Tetrahymena geleii, T. vorax, Glaucoma scintillans and Colpidium campylum), grown in pure culture, are given.

2. The two species of Tetrahymena are able to utilize dissolved nutritive materials while Glaucoma and Colpidium are dependent upon particulate materials in the media.

3. The growth of T. geleii is slightly accelerated by some factor in yeast and by the presence of fermentable carbohydrates (dextrose, levulose, maltose, cellobiose and starch) while inhibition of the growth of T. vorax results when these materials are present.

4. The maximum yield of Glaucoma and Colpidium is greatly increased by fermentable carbohydrates.

5. Colpidium fails to ferment cellobiose but, unlike the other three species, does ferment sucrose.

6. Galactose, arabinose and xylose, while not fermented by any of the four species of ciliates, inhibit the growth of all.

7. The optimum range of pH values for T. geleii (strain W) is wide (pH 5.6 — pH 8.0); T. vorax is slightly more limited (pH 6.2 — pH 7.6); Glaucoma is limited to the acid range (pH 5.6 — pH 6.8), while Colpidium grows best at pH 5.4.

8. In the cases of Tetrahymena geleii, T. vorax, and Glaucoma scintillans when single ciliates from the logarithmic growth phase are inoculated into 500 ml. of media (initial inoculum = 0.002 cells per ml.) there is no lag phase and the generation time is not reduced (as compared with controls).

9. Single Colpidium campylum inoculated into 500 ml. of media often die. When a culture is established the generation time is longer and the maximum yield is smaller than when many cells are inoculated. It is suggested that these results are correlated with slight toxicity of the medium.