@article{04c2bad8-bbd0-4acd-965b-26bc9b44feae,
author = {Tatsuomi Matsuoka, Yoichiro Sogame, Rikiya Nakamura, Yuya Hasegawa, Mikihiko Arikawa, Futoshi Suizu},
title = {Antifreeze Water-Rich Dormant Cysts of the Terrestrial Ciliate Colpoda cucullus Nag-1 at −65 ℃: Possible Involvement of Ultra-Antifreeze Polysaccharides},
journal = {Acta Protozoologica},
volume = {2020},
number = {Volume 59, Issue 3-4},
year = {2021},
issn = {0065-1583},
pages = {141-147},keywords = {water-rich resting cyst; antifreeze; polysaccharides; osmolarity},
abstract = {We found that the water-rich (osmolality below 0.052 Osm/l) wet resting cysts of the soil ciliate Colpoda cucullus Nag-1 were tolerant to extremely low temperature (−65℃). When cell fluid obtained from the resting cysts was cooled at −65℃, small particles of ice crystals did not grow into large ice crystals. At −65℃, the cysts shrank due to an outflow of water, because a vapor pressure difference was produced between the cell interior and freezing surrounding medium. The osmolality of these shrunk cells was estimated 0.55 Osm/l, and the freezing point depression of the shrunk cell fluid was estimated to be 1.02℃. Hence, the antifreeze ability of wet cysts at −65℃can not be explained by freezing point depression due to elevation of cytoplasmic osmolality.

	The cytoplasm of resting cysts was vividly stained red with periodic acid-Schiff (PAS) and stained purple with toluidine blue. On the other hand, the excystment-induced cysts were not stained with PAS, and exhibited a loss of the antifreeze activity. PAS staining of SDSPAGE gel obtained from encysting Colpoda cells showed that a large amount of PAS-positive macromolecules accumulated as the encystment stage progressed. These results suggest that antifreeze polysaccharides may be involved in the antifreeze activity of C. cucullus Nag-1 dormant forms.},
doi = {10.4467/16890027AP.20.011.13266},
url = {https://ejournals.eu/en/journal/acta-protozoologica/article/antifreeze-water-rich-dormant-cysts-of-the-terrestrial-ciliate-colpoda-cucullus-nag-1-at-65-possible-involvement-of-ultra-antifreeze-polysaccharides}
}