Some bacteria breathe oxygen, but many use other forms of respiration. Strictly speaking, bacteria do not “breathe” as humans and other animals do, but they must still engage in the act of cellular respiration. Cellular respiration is the method by which cells convert chemicals into energy that the cell needs to stay alive. Bacteria are an incredibly diverse collection of organisms who respire in a wide variety of ways.
To execute cellular respiration, the cell needs an energy source, such as glucose, and an electron acceptor. This process allows the cell to produce adenosine triphosphate, the energy currency for cells. Abbreviated ATP, adenosine triphosphate can power any of the functions necessary in the cell. Many cells use oxygen as an electron acceptor, but some bacteria use other electron acceptors in the reaction.
Some bacteria use sulfate, nitrate, sulfur or fumarate as electron acceptors in the process of cellular respiration. Such bacteria are called anaerobic, as they inhabit areas without oxygen. However, oxygen is a much more efficient electron acceptor than these other chemicals, so anaerobic respiration is much more efficient.
Early in the history of eukaryotic cells, ancient aerobic bacteria were engulfed by the larger cells, who used them to produce ATP inside the cells. These ancient bacteria evolved into the organelles called mitochondria, which produce the energy for modern eukaryotic cells.