Effects of Cell Repair on the Excystment of Irradiated Cysts and Cell Growth of Vegetative Cells Excysted from Irradiated Cysts in Colpoda cucullus

摘要

A eukaryotic unicellular organism, Colpoda, undergoes cryptobiosis by forming resting cysts (encystment). Resting cysts can tolerate various environmental stresses, however, the metabolism is stopped. On alleviation of the stresses, these cysts can promptly revert to vegetative cells (excystment). In our previous study, we found that Colpoda cysts and dry cysts (cysts in a desiccated condition) have high tolerance to gamma irradiation. In addition, we recently revealed that Colpoda cysts can repair cell damage caused by gamma irradiation, whereas dry cysts cannot. In this study, we examined the influence of gamma irradiation and cell repair on cell growth in Colpoda. The results showed that the growth of vegetative cells excysted from irradiated cysts was more suppressed than that of vegetative cells excysted from non-irradiated cysts. The suppression of cell growth following irradiation was slightly overcome by incubation of the cystic state after irradiation. These results suggest that gamma irradiation causes problems in cell growth for Colpoda vegetative cells following their excystment.