Development of Vacuoles and Vacuolar H+‐ATPase Activity under Extremely High CO2 Conditions in Chiorococcum littorale Cells

The number and cross‐sectional area of vacuoles in Chlorococcum littorale cells visualized with a differential interfer ence fluorescence microscope increased after their transfer from air to 40% CO2. An immunological observation indicated that the level of subunit B of vacuolar H*ATPase also increased under 40% CO2 conditions. The activity of nitrate‐sensitive ATP‐ase associated with the vacuolar membrane was 2–fold higher in 40% CO2‐‐grown cells than in air‐grown cells. The effects of inhi bitors on the ATPase activity confirmed that these activities were derived from vacuolar‐type H‐ATPase. These results sug gest that vacuole development associated with that of vacuolar H+‐ATPase occurred during the acclimatization of C. littorale cells to extremely high CO2 conditions.