Alkaline Response of a Halotolerant Alkaliphilic Halomonas Strain and Functional Diversity of Its Na+ (K+)/H+ Antiporters
Alkaline Response of a Halotolerant Alkaliphilic Halomonas Strain and Functional Diversity of Its Na+ (K+)/H+ Antiporters
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DOI：
10.1074/jbc.m116.751016
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发表时间：
2016-12-09
影响因子：
4.8
通讯作者：
Xu, Ping
中科院分区：
文献类型：
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作者：
Cheng, Bin;Meng, Yiwei;Xu, Ping
盐生单胞菌Y2是一株产自高碱度(pH>；11.0)高钠制浆废水的耐盐嗜碱菌株。对该分离株的转录组分析表明，该菌株可能使用多种运输系统来维持pH动态平衡。特别是，编码四个可能的Na+/H+逆向转运蛋白的基因在酸性或碱性条件下差异表达。来自异源表达和突变研究的进一步证据表明，Halomonas sp.Y2以分工的方式利用其Na+/H+逆向转运蛋白来应对盐碱环境。Ha-NhaD2在大肠杆菌中表现出较强的抗Na+(Li+)能力和较高的转运活性；Delta Ha-nhaD2突变体在高Na+(Li+)浓度(6.2、8.0和10.0)下表现出生长抑制，表明其在渗透平衡中起生理作用。相反，Ha-NhaD1在离子输出和pH动态平衡方面的活性要弱得多。HA-MRP表现出与一些嗜碱性芽孢杆菌和中性粒细胞的MRP转运蛋白相似的性质组合。这与一些中性粒细胞MRP逆向转运蛋白的离子转运谱一样，赋予了缺乏大肠杆菌的菌株明显的Na+(Li+，K+)抗性。相反，与嗜碱芽孢杆菌相似，Ha-MRP在盐生单胞菌的pH动态平衡中起着中心作用。Y2.高浓度的Na+(Li+，K+)对Ha-MRP突变株有较强的抑制作用，但只能在碱性条件下进行。HA-NhaP是一种K+/H+逆向转运蛋白，在酸性和碱性胁迫下都表现出很强的K+抗性。
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 Delta Ha-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.