Transcriptional profiling of Staphylococcus aureus during growth in 2 M NaCl leads to clarification of physiological roles for Kdp and Ktr K+ uptake systems.
Transcriptional profiling of Staphylococcus aureus during growth in 2 M NaCl leads to clarification of physiological roles for Kdp and Ktr K+ uptake systems.
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DOI：
10.1128/mbio.00407-13
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发表时间：
2013-08-20
期刊：
影响因子：
6.4
通讯作者：
Krulwich TA
中科院分区：
文献类型：
--
作者：
Price-Whelan A;Poon CK;Benson MA;Eidem TT;Roux CM;Boyd JM;Dunman PM;Torres VJ;Krulwich TA
金黄色葡萄球菌表现出异常高的耐盐性和耐Na+性，这些特性支持其在各种宿主环境和保存食品中的存活。这些特征的遗传基础还不清楚。我们比较了在含有和不含有2 M NaCl的复合培养基中生长的金黄色葡萄球菌的转录谱。在高渗透压介质和Na+中生长的刺激因子包括参与K+、其他相容性溶质、唾液酸和糖的摄取的基因;胶囊生物合成;以及氨基酸和中枢代谢。定量PCR分析表明，位点反应不同，从对方施加高渗透压升高的NaCl与蔗糖。高亲和力K+吸收（kdp）基因和胶囊生物合成（cap 5）基因需要的双组分系统KdpDE充分诱导渗透胁迫，与kdpA诱导更多的NaCl和cap 5 B诱导更多的蔗糖。针对K+输入者，我们鉴定了属于低亲和力Trk/Ktr家族的三个金黄色葡萄球菌基因，其编码两种膜蛋白（KtrB和KtrD）和一种辅助蛋白（KtrC）。在不存在渗透胁迫的情况下，ktr基因转录本比kdpA转录本丰富得多。金黄色葡萄球菌kdpA的破坏导致在低K+条件下的生长缺陷，ktrC的破坏导致在2 M NaCl中的显著缺陷，并且ΔktrC ΔkdpA双突变体表现出两种表型。金黄色葡萄球菌Ktr转运蛋白在高NaCl下的保护作用与先前的指示一致，即通过维持高细胞质K+浓度来减轻Na+和渗透压挑战。人们普遍认为，金黄色葡萄球菌的耐盐性和耐Na+性对于非嗜盐菌来说异常高，并支持其在人类中定植、致病和在食物中生长的能力。尽管如此，这些特性的分子基础还没有很好的定义。金黄色葡萄球菌对高浓度（2 M）NaCl的全基因组反应显示预期基因上调，例如广泛参与支持耐盐性的相容性溶质转运蛋白基因。一个高亲和力的钾吸收系统，KdpFABC，上调，虽然它通常在非常低的K+条件下发挥生理作用。在较高的K+浓度，低亲和力和更高的表达类型的K+转运系统，Ktr转运蛋白，被证明在高Na+耐受中发挥重要作用。这项研究说明了细胞的K+状态对金黄色葡萄球菌耐Na+的重要性，并强调了单价阳离子循环在这种病原体中的重要性。
Staphylococcus aureus exhibits an unusually high level of osmotolerance and Na+ tolerance, properties that support survival in various host niches and in preserved foods. The genetic basis of these traits is not well understood. We compared the transcriptional profiles of S. aureus grown in complex medium with and without 2 M NaCl. The stimulon for growth in high-osmolality media and Na+ included genes involved in uptake of K+, other compatible solutes, sialic acid, and sugars; capsule biosynthesis; and amino acid and central metabolism. Quantitative PCR analysis revealed that the loci responded differently from each other to high osmolality imposed by elevated NaCl versus sucrose. High-affinity K+ uptake (kdp) genes and capsule biosynthesis (cap5) genes required the two-component system KdpDE for full induction by osmotic stress, with kdpA induced more by NaCl and cap5B induced more by sucrose. Focusing on K+ importers, we identified three S. aureus genes belonging to the lower-affinity Trk/Ktr family that encode two membrane proteins (KtrB and KtrD) and one accessory protein (KtrC). In the absence of osmotic stress, the ktr gene transcripts were much more abundant than the kdpA transcript. Disruption of S. aureus kdpA caused a growth defect under low-K+ conditions, disruption of ktrC resulted in a significant defect in 2 M NaCl, and a ΔktrC ΔkdpA double mutant exhibited both phenotypes. Protective effects of S. aureus Ktr transporters at elevated NaCl are consistent with previous indications that both Na+ and osmolality challenges are mitigated by the maintenance of a high cytoplasmic K+ concentration. There is general agreement that the osmotolerance and Na+ tolerance of Staphylococcus aureus are unusually high for a nonhalophile and support its capacity for human colonization, pathogenesis, and growth in food. Nonetheless, the molecular basis for these properties is not well defined. The genome-wide response of S. aureus to a high concentration, 2 M, of NaCl revealed the upregulation of expected genes, such as those for transporters of compatible solutes that are widely implicated in supporting osmotolerance. A high-affinity potassium uptake system, KdpFABC, was upregulated, although it generally plays a physiological role under very low K+ conditions. At higher K+ concentrations, a lower-affinity and more highly expressed type of K+ transporter system, Ktr transporters, was shown to play a significant role in high Na+ tolerance. This study illustrates the importance of the K+ status of the cell for tolerance of Na+ by S. aureus and underscores the importance of monovalent cation cycles in this pathogen.