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Updated: Aug 12, 2026
Generation and Isolation of Cell Cycle-arrested Cells with Complex Karyotypes
Published on: April 13, 2018
G1-phase arrest is not a prerequisite for encystment in Physarum
R W Anderson1, J Dee, J L Foxon
1Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom. r.anderson@sheffield.ac.uk
Abstract:
Amoebae of the Myxomycete Physarum polycephalum form resistant, walled cysts when the food bacteria in a culture have been consumed. No G1 phase has been detected in the vegetative amoebal cell cycle, most of which comprises the G2 phase. Mature cysts are also in G2, but it has been reported that a G1 phase of roughly 24 h, followed by an S phase, is obligatory prior to encystment. We used flow cytometry to determine the distribution of DNA contents in amoebal cultures at intervals during vegetative growth and encystment. In all cultures, the cells were predominantly in G2 phase, and the percentage of cells with G1 DNA content remained very low. We conclude that an extended G1 phase of 24 h did not occur in our cultures and cannot be a prerequisite for encystment.
Insights
Physarum polycephalum amoebae encyst without a lengthy G1 phase. Flow cytometry revealed cells predominantly remain in G2 phase during growth and encystment, challenging prior assumptions.
Area of Science:
- Cell Biology
- Mycology
- Developmental Biology
Background:
- The slime mold *Physarum polycephalum* forms resistant cysts upon nutrient depletion.
- Vegetative amoebae typically lack a G1 phase, with most cells in G2.
- Previous studies suggested an obligatory 24-hour G1 phase precedes encystment.
Purpose of the Study:
- To investigate the cell cycle dynamics during encystment in *Physarum polycephalum*.
- To determine if a prolonged G1 phase is a prerequisite for cyst formation.
Main Methods:
- Utilized flow cytometry to analyze DNA content distribution.
- Monitored cell cycle phases during vegetative growth and induced encystment.
Main Results:
- *Physarum polycephalum* cultures predominantly exhibited cells in the G2 phase.
- A very low percentage of cells displayed G1 DNA content throughout the experiment.
- No extended G1 phase was detected preceding encystment.
Conclusions:
- An obligatory 24-hour G1 phase is not required for encystment in *Physarum polycephalum*.
- The vegetative cell cycle and encystment process primarily occur within the G2 phase.
