Physiological roles of three Na+/H+ antiporters in the halophilic bacterium Vibrio parahaemolyticus
Physiological roles of three Na+/H+ antiporters in the halophilic bacterium Vibrio parahaemolyticus
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DOI：
10.1111/j.1348-0421.2005.tb03662.x
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发表时间：
2005-01-01
影响因子：
2.6
通讯作者：
Tsuchiya, T
中科院分区：
文献类型：
--
作者：
Kuroda, T;Mizushima, T;Tsuchiya, T
构建了缺失3个Na+/H+逆向转运蛋白(NhaA、NhaB、NHAD)的副溶血性弧菌突变株。与亲本菌株相比，Delta Nha Delta菌株对LiCl的生长表现出明显更高的敏感性。Delta nhaA和Delta nhaB菌株对LiCl具有较高的敏感性。缺失这三种转运蛋白的突变株XACabd不能在500 mM的LiClpH 7.0或50 mM的pH 8.5下生长。XACabd突变体对pH 8.5的1.0mNaC l也很敏感。这些结果表明，Na+/H+逆向转运蛋白，尤其是NhaA，是导致植物对LiCl2和高浓度NaCl2产生抗性的原因之一。Delta nhaB株外翻膜泡的Na+/H+和Li+/H+反转运活性降低。然而，当细胞培养在pH 8.5时，Delta nhaB菌株的Li+/H+反转运活性是Delta nhaA菌株的两倍。NhaA和nhaB的表达似乎在一定程度上依赖于介质pH。此外，呼吸Na+泵的有效抑制剂HQNO(2-庚基-4-羟基喹啉N-氧化物)能抑制XACabd的生长，但不能抑制野生型菌株的生长。此外，XACabd在低渗胁迫下的存活率低于野生型菌株。Na+/H+逆向转运蛋白可能参与了低渗胁迫下的渗透调节。基于这些发现，我们认为副溶血性弧菌的Na+/H+逆向转运蛋白与呼吸Na+泵在离子平衡中具有协同作用。
Vibrio parahaemolyticus mutants lacking three Na+/H+ antiporters (NhaA, NhaB, NhaD) were constructed. The Delta nha Delta strains showed significantly higher sensitivity to LiCl regarding their growth compared to the parental strain. The Delta nhaA and Delta nhaB strains exhibited higher sensitivities to LiCl. The mutant XACabd lacking all of the three antiporters could not grow in the presence of 500 mm LiCl at pH 7.0, or 50 mm at pH 8.5. The XACabd mutant was also sensitive to 1.0 m NaCl at pH 8.5. These results suggest that Na+/H+ antiporters, especially NhaA, are responsible for resistance to LiCl and to high concentrations of NaCl. Reduced Na+/H+ and Li+/H+ antiport activities were observed with everted membrane vesicles of Delta nhaB strains. However, Li+/H+ antiport activities of Delta nhaB strains were two times higher than those of Delta nhaA strains when cells were cultured at pH 8.5. It seems that expression of nhaA and nhaB is dependent on medium pH to some extent. In addition, HQNO (2-heptyl-4-hydroxyquinoline N-oxide), which is a potent inhibitor of the respiratory Na+ pump, inhibited growth of XACabd, but not of the wild type strain. Moreover, survival rate of XACabd under hypoosmotic stress was lower than that of wild type strain. It is likely that the Na+/H+ antiporters are involved in osmoregulation under hypoosmotic stress. Based on these findings, we propose that the Na+/H+ antiporters cooperate with the respiratory Na+ pump in ionic homeostasis in V parahaemolyticus.