Final answer:
Bacteria do not use NADH and oxygen reactions because they have alternative ways of making ATP, such as chemiosmosis and fermentation. Fermentations result in the production of fewer ATPs, as NADH + H+ is not oxidized through the electron transport chain. This is why bacteria have different options for energy production.
Step-by-step explanation:
Bacteria tend to not use NADH and oxygen reactions mainly because they have options for making ATP other than aerobic respiration.
They can generate ATP through chemiosmosis in both aerobic and anaerobic respiration, or they can ferment sugars. In fermentations, NADH + H+ is not oxidized through the electron transport chain, but by lactate dehydrogenase, resulting in the production of fewer ATPs. This is why bacteria do not rely heavily on NADH and oxygen reactions.