f Contact with a solid substratum induces cysts in axenic cultures of Physarum polycephalum amoebae: mannitol-induced detergent-resistant cells are not true cysts
- Authors: Jennifer Dee, Jennifer L. Foxon, Wendy Hill, Evaline M. Roberts, Muriel H. Walker
- Author for correspondence: Jennifer Dee. Tel: +44 116 252 3426. Fax: +44 116 252 3378. e-mail: jjd2@:le.ac.uk
- Microbiology, April 1997 143: 1059-1069, doi: 10.1099/00221287-143-4-1059
- Subject: Development And Structure
- Published Online:
Previous workers reported that Physarum polycephalum amoebae cultured in liquid axenic medium were induced to form cysts by the addition of mannitol. Their criterion for encystment was the formation of detergent (Triton)-resistant cells (TRC). In this study the frequencies of TRC in suspensions of amoebae from various treatments were compared with counts of cell types identified by transmission electron microscopy. Amoebae treated with mannitol in axenic liquid culture formed 50% TRC after 17 h but no walled cysts were found. It was concluded that TRC induced by mannitol were dense, rounded cells without walls. In contrast, TRC formed after growth to stationary phase on bacterial lawns were walled cells. When resuspended in growth medium, most mannitol-induced TRC reverted to active amoebae within a few minutes, whereas TRC formed on bacteria remained Triton resistant for many hours. It was concluded that delayed reversion of TRC was a more reliable indication of wall formation than Triton resistance alone. Transfer of amoebae from liquid culture to the surface of diluted axenic agar medium resulted in the formation of walled cysts identical in appearance with those formed on bacterial lawns. The results indicated that efficient encystment requires a solid substratum as well as nutrient deprivation.
© Society for General Microbiology 1997 | Published by the Microbiology Society
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