Energy Production

Bacteria can produce ATP either aerobically or anaerobically. Anaerobic bacteria (in the absence of oxygen) produce ATP by breaking down nutrients into simpler metabolites, and using the energy released from the process to form ATP from ADP.  Aerobic bacteria produce ATP more efficiently by further oxidizing (in the presence of oxygen) these resultant metabolites to generate a promotive gradient along their inner membrane. The enzymes that catalyze the oxidation are membrane bound, and they use the energy released from the oxidation process to pump H+ from the cytosol to the other side of the membrane. As the H+ ions pass back into the membrane through specialized pumps, ATP is generated in an active site on these pumps. Mitochondria produce ATP in exactly the same way. In fact, given the overwhelming overlap in the genetic sequences and biochemical processes between mitochondria and aerobic bacteria, it is now widely accepted that mitochondria evolved by endosymbiosis of a proteobacterial ancestor within eukaryotic cells.