Some bacteria are facultative anaerobes, which usually produce atp by aerobic respiration but are also capable of switching to fermentation when there is a lack of in their environment

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.