@article{oai:obihiro.repo.nii.ac.jp:00004729,
 author = {Nakamura, Rikiya and Sogame, Yoichiro and Arikawa, Mikihiko and Suizu, Futoshi and Matsuoka, Tatsuomi},
 issue = {1-2},
 journal = {The Journal of protozoology research},
 month = {},
 note = {application/pdf, In parasitic unicellular eukaryotes, the tolerance to the pH (1-1.5) of gastric acid is a crucial
survival strategy so that they can proliferate in the intestinal tract. We found that the resting
cysts of non-parasitic soil ciliate Colpoda cucullus Nag-1 showed a strong tolerance to both
extremely low and high pH. The purpose of this study was to explore the tolerance
mechanism to extreme pH. Most cysts were alive after exposure to 0.1 M HCl (pH 1) for 4
h, or after exposure to 0.1 M NaOH (pH 13) for 3 h. Such tolerance to extreme pH is acquired
gradually over several days after encystment induction. The resting cysts were reversibly
dehydrated by osmotic pressure when they were transferred from water to 0.1 M HCl or 0.1
M NaOH. This result suggests that H+/Cl- and Na+/OH- may diffuse through the cyst wall to
reach the plasma membrane. Acid tolerance was reduced in the presence of protonophore
(CCCP), suggesting that less permeability of the cyst plasma membrane to H+ may be
responsible for acid tolerance.},
 pages = {38--46},
 title = {Tolerance of Colpoda cucullus Nag-1 wet resting cysts to extreme pH (pH 1 and 13): Implications of less permeability of the cyst membrane to H+ and OH},
 volume = {30},
 year = {2020}
}