The distribution of DNA content of symbiotic Chlorella algae freshly isolated from green hydra was compared with that of cultured Chlorella of the NC64A strain, using flow cytometry. In nonlogarithmic cultures of NC64A most cells had accumulated in G1 phase, while in logarithmic cultures a peak containing cells in S phase and mitosis could be distinguished from the larger G1 peak. However, symbiotic algae showed a single broad peak in which there was no clear distinction between G1 and S phase/mitosis. When hydra were starved for a prolonged period, inhibiting host cell and algal division, the DNA content of the symbiotic algae slowly increased, and the number of daughter cells produced after a single feeding increased with the length of the preceding period of starvation. This suggests that symbiotic algae are able to cycle slowly through S phase, but unless the host is fed they cannot traverse into mitosis and complete the cell division cycle. No significant difference in cell size was found between algae producing either four or eight daughter cells after 1-day- or 22-day-starved hydra were fed, suggesting that algal cell size did not determine the number of daughter cells produced. Instead, this may be dependent upon the length of time the cell had spent in S phase prior to receiving the, as yet unknown, stimulus to enter into mitosis.
The cell cycle of symbiotic Chlorella. IV. DNA content of algae slowly increases during host starvation of green hydra
P.J. McAuley, L. Muscatine; The cell cycle of symbiotic Chlorella. IV. DNA content of algae slowly increases during host starvation of green hydra. J Cell Sci 1 September 1986; 85 (1): 73–84. doi: https://doi.org/10.1242/jcs.85.1.73
Download citation file:
Advertisement
Cited by
JCS Journal Meeting 2023: Imaging Cell Dynamics

Our 2023 Journal Meeting on ‘Imaging Cell Dynamics’ will be held from 14-17 May 2023 in Lisbon, Portugal. Due to popular demand, we can currently only accept applications for online attendance. Apply now to attend this meeting virtually. Registration deadline: 31 March.
Call for papers: Cell and Tissue Polarity
-PolarityCFP.png?versionId=4696)
We are welcoming submissions for our next special issue, which will focus on ‘Cell and tissue polarity’ and will be guest edited by David Bryant. Submission deadline: 15 July.
Editorial: Publishing where it matters
Editor-in-Chief Michael Way outlines Journal of Cell Science’s plans for the upcoming year and introduces Seema Grewal as our new Executive Editor.
preLights 5th Birthday webinar

preLights, our preprint highlighting service, is celebrating its 5th birthday this year. To mark the occasion, join us online on 14 March 2023 at 16:00 GMT for a discussion, led by four preLights alumni, on how to identify and navigate the challenges and opportunities while shaping your career as an early-career researcher.
Cell Scientists to Watch

As a community-focused journal, Journal of Cell Science is keen to support the next generation of cell biologists. Check out Cell Scientists to Watch, our interview series featuring talented researchers who have recently set up their own labs.