Evaluation of intracellular Ca~(2+) concentration by fura 2 ratiometry in encystment-induced Colpoda cucullus

摘要

In Colpoda cucullus, the signaling pathways for encystment induction involving protein phosphorylation have been believed to be triggered by an increase in the intracellular Ca~(2+) concentration promoted by cell-to-cell mechanical contact due to overpopulation. By means of fura 2 ratiometry, the present study showed that the intracellular Ca~(2+) concentration was actually elevated when vegetative cells were induced to encyst by being suspended at a high cell density in the presence of external free Ca~(2+) and suppressed by chelating external Ca~(2+). This result strongly suggests that an increase in the intracellular Ca~(2+) concentration caused by an inflow of Ca~(2+) promoted by cell-tocell mechanical contact due to overpopulation enhances the rate of encystation in Colpoda cucullus.