ABSTRACT
Sha (also known as Mrp/Mnh/Pha) is a Na+/H+ antiporter encoded by a cluster of six or seven genes that probably form a multisubunit transport complex. The Sha system is important for the homeostasis of H+, Na+, and other monovalent cations and plays a critical role in various functions, including alkaliphily, sporulation, and symbiosis. Here, we characterized the sha homologue genes from the opportunistic pathogen Pseudomonas aeruginosa, which exist as a cluster of six genes (PA1054 to PA1059). The gene cluster PA1054 to PA1059, but not the cluster with a deletion of PA1054, complemented a growth defect in the presence of 0.2 M NaCl and a defect in Na+/H+ antiport activity of the Escherichia coli TO114 mutant lacking the three major Na+/H+ antiporters, indicating that genes PA1054 to PA1059 are responsible for Na+/H+ antiport activity. We disrupted PA1054 (a shaA homologue gene) and determined its effect on Na+ tolerance during growth, Na+ efflux, and pathogenicity in mice. Disruption of PA1054 resulted in severe Na+ sensitivity during growth and decreased Na+ efflux activity. In mice, the deletion mutant of PA1054 also exhibited an attenuated virulence in systemic, pulmonary, and urinary tract infections and also a decrease in colonization of the infected organs. From these results, we conclude that the genes PA1054 to PA1059 encode a Na+/H+ antiporter that is largely responsible for Na+ extrusion in P. aeruginosa and has a role in the infection of the pathogen. We propose to designate PA1054 to PA1059 as the sha (sodium hydrogen antiporter) genes, shaABCDEFG.
Subject(s)
Bacterial Proteins/genetics , Multigene Family , Pseudomonas aeruginosa/genetics , Sodium-Hydrogen Exchangers/genetics , Animals , Culture Media , Female , Gene Deletion , Male , Mice , Pseudomonas aeruginosa/growth & development , Pseudomonas aeruginosa/pathogenicity , Sodium Chloride , Sodium-Hydrogen Exchangers/metabolism , VirulenceABSTRACT
The sodium/hydrogen antiporter (Sha, identical to multiple resistance and pH adaptation: Mrp) encoded by shaABCDEFG is considered to be the major Na+ excretion system in Bacillus subtilis. We constructed deletion mutants of each sha (=mrp) gene and found that a shaE mutant showed lower Na+ sensitivity compared to the other mutants with respect to the growth, sporulation and Na+ efflux activity. ShaE may have a dissimilar role to other Sha proteins in transport functions.
