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Journal of Bacteriology, August 2005, p. 5242-5248, Vol. 187, No. 15
0021-9193/05/$08.00+0     doi:10.1128/JB.187.15.5242-5248.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Characterization of a Multigene-Encoded Sodium/Hydrogen Antiporter (Sha) from Pseudomonas aeruginosa: Its Involvement in Pathogenesis

Environmental Molecular Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan,¹ Pharmacology Research Laboratories, Astellas Pharma Inc., 2-chome, 1-6, Kashima, Yodogawa-ku, Osaka 532-8514, Japan,² Fermentation and Biotechnology Laboratories, Astellas Pharma Inc., 156 Nakagawara, Shinkawa-cho, Nishikasugai-gun, Aichi 452-0915, Japan,³ Graduate School of Integrated Science, Yokohama City University, Tsurumi, Kanagawa 230-0045, Japan⁴

Received 22 November 2004/ Accepted 12 May 2005

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.

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