THE PRECISE CONTROL OF GROWTH IN A PURE CULTURE OF A CILIATE, GLAUCOMA PYRIFORMIS

¹ From the Zoölogy Department, Johns Hopkins University, and the Marine Biological Laboratory, Woods Hole

1. The strain of Glaucoma pyriformis reported upon in this paper will not grow in peptone in pure culture, or in this plus a fine suspension of insoluble particles of extracted yeast.

Yeast extract (Difco), particle-free, supports a division rate of 6.86.

Whole yeast (Difco—autoclaved) plus either peptone or yeast extract supports division rates from 7.65 to 8.02.

Media more complex than this do not increase the division rate.

If the whole yeast added to the yeast extract is fractionally sterilized rather than autoclaved, marked increase in division rate results.

2. There is but one optimum hydrogen ion concentration. This is in the region of pH 7.

3. When 600 to 2,000 glaucomas are inoculated in 50 cc. of medium, the division rate is 7.89 to 8.02 for the first day. When larger numbers are inoculated the division rate is lower.

4. If one dividing glaucoma is inoculated, the mean division rate (48 hours) varies from 7.65 to 7.88.

5. Observation of isolated organisms in shallow dishes revealed marked irregularity in the interval required for division: from 2 hours and 45 minutes for the shortest interval to 4 hours and 25 minutes for the longest. The mean was 3 hours and 25 minutes, corresponding to a division rate of 7.

6. Counts of growth in less than 24 hours apparently demonstrate a lag in early growth. No definite conclusions were drawn because of the large error resulting from counting low concentrations of ciliates.