The second, less common adaptation, is the selective intake of potassium (K) ions into the cytoplasm. In exchange, the organism pumps sodium (Na) ions out with the help of the sodium-potassium pump. Ions of sodium may be used instead of potassium, but potassium is the most common. This adaptation is only used by one order of bacteria and one family of Archaea. An advantage to this method is that it uses much less energy than the adaption above. The main disadvantage to this adaption is that all of the machinery inside the cell (enzymes, structural proteins, etc.) must be adapted to high levels of non-organic ions, and high salt levels. This is much more demanding than the adaptation described above.