A facultative anaerobic bacterium can survive both aerobic and anaerobic conditions. Under both conditions, the cell maintains a proton-motive force across the plasma membrane that drives many cellular processes including nutrient import. Under aerobic conditions, the proton-motive force is produced by a respiratory chain. What is the mode of action of the plasma membrane ATP synthase in this bacterium under aerobic conditions: ATP-hydrolysis mode (H) or ATP-synthesis mode (S)? Write down H or S as your answer.