title: Alkaline Response of a Halotolerant Alkaliphilic Halomonas Strain and Functional Diversity of Its Na+(K+)/H+ Antiporters.
abstract: Halomonas sp. Y2 is a halotolerant alkaliphilic strain from Na+-rich pulp mill wastewater with high alkalinity (pH >11.0). Transcriptome analysis of this isolate revealed this strain may use various transport systems for pH homeostasis. In particular, the genes encoding four putative Na+/H+antiporters were differentially expressed upon acidic or alkaline conditions. Further evidence, from heterologous expression and mutant studies, suggested that Halomonas sp. Y2 employs its Na+/H+antiporters in a labor division way to deal with saline and alkaline environments. Ha-NhaD2 displayed robust Na+(Li+) resistance and high transport activities in Escherichia coli; a ΔHa-nhaD2 mutant exhibited growth inhibition at high Na+(Li+) concentrations at pH values of 6.2, 8.0, and 10.0, suggesting its physiological role in osmotic homeostasis. In contrast, Ha-NhaD1 showed much weaker activities in ion exporting and pH homeostasis. Ha-Mrp displayed a combination of properties similar to those of Mrp transporters from some Bacillus alkaliphiles and neutrophiles. This conferred obvious Na+(Li+, K+) resistance in E. coli-deficient strains, as those ion transport spectra of some neutrophil Mrp antiporters. Conversely, similar to the Bacillus alkaliphiles, Ha-Mrp showed central roles in the pH homeostasis of Halomonas sp. Y2. An Ha-mrp-disrupted mutant was seriously inhibited by high concentrations of Na+(Li+, K+) but only under alkaline conditions. Ha-NhaP was determined to be a K+/H+antiporter and shown to confer strong K+resistance both at acidic and alkaline stresses.
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
authors: Bin
authors: B
authors: Cheng
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
authors: Yiwei
authors: Y
authors: Meng
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
authors: Yanbing
authors: Y
authors: Cui
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
authors: Chunfang
authors: C
authors: Li
authors: the State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors: Fei
authors: F
authors: Tao
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.
authors: Huijia
authors: H
authors: Yin
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and ycy21th@sdu.edu.cn.
authors: Chunyu
authors: C
authors: Yang
authors: From the State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100 and.|the State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors: Ping
authors: P
authors: Xu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020632:Halomonas / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D027961:Potassium-Hydrogen Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D027961:Potassium-Hydrogen Antiporters; D017923:Sodium-Hydrogen Exchangers
keywords: membrane protein; pH regulation; potassium transport; sodium-proton exchange; stress response; transcriptomics