Sodium ion transportation system and its possible mechanisms in Bacteria
细菌钠离子输出系统的类型及其可能机制

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.