Sodium ion transportation system and its possible mechanisms in Bacteria

Abstract:

Sodium ion with high concentration is toxic to living cells, and microorganisms adapt to the environment containing high concentration of salt by the strategies of salt-in-cytoplasm and compatible solutes. The Na＋ extrusion system plays important roles in maintaining cytoplasmic Na^＋ homeostasis and pH level in microbial cells. Two possible mechanisms of Na⁺ circulation across the cytoplasmic membrane have been proposed, namely primary Na⁺ pump and secondary Na⁺/H⁺ antiporter. Primary sodium pumps coupled the extrusion of Na^＋ to respiration, and the activity of which was insensitive to uncoupler CCCP (carbonyl-cyanide m-chlorophenylhydrazone). There were two types of secondary Na⁺/H⁺ antiporters-encoding genes designated single gene and multiple subunits, respectively. The types of transportation systems for Na^＋, possible mechanisms of Na^＋ extrusion, and projects for further study in bacteria are reviewed.