CHAPTER 2: Sodium. Its Role in Bacterial Metabolism

This chapter reviews the multiple roles of the sodium ion Na⁺ in the physiology of bacteria. Virtually all cells need to extrude Na⁺ in order to maintain a constant internal environment. In many bacteria, transport of Na⁺ out of the cell has an important additional role in harnessing energy and distributing it within the cell. In these cases, Na⁺ takes on the role otherwise played by H⁺ in chemiosmotic energetic functions. As a means of exploring these functions, we will examine a subset of Na⁺ transport enzymes that are prototypical of the various catalytic processes involved in Na⁺ homeostasis and Na⁺ chemiosmosis.