An Essential Role for (p)ppGpp in the Integration of Stress Tolerance, Peptide Signaling, and Competence Development in Streptococcus mutans.
An Essential Role for (p)ppGpp in the Integration of Stress Tolerance, Peptide Signaling, and Competence Development in Streptococcus mutans.
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DOI：
10.3389/fmicb.2016.01162
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发表时间：
2016
影响因子：
5.2
通讯作者：
Burne RA
中科院分区：
文献类型：
--
作者：
Kaspar J;Kim JN;Ahn SJ;Burne RA
居住在人类口腔中的微生物受到环境不断变化的影响。为了克服这些挑战并获得竞争优势，口腔链球菌采用了许多适应策略，其中许多策略似乎与遗传能力的发展交织在一起。在这里，我们证明了控制变形链球菌（人类龋齿的主要病原）能力发展的调控电路，通过分子警报器(p)ppGpp与关键的应激耐受途径相结合。我们首先观察到，与野生型菌株UA159不同，不产生(p)ppGpp的菌株（ΔrelAPQ, (p)ppGpp0）的生长对comX诱导肽（XIP）的生长抑制不敏感，尽管(p)ppGpp0菌株通过ComRS途径对替代sigma因子comX的XIP依赖性激活并未受损。(p)ppGpp0突变体中a (p)ppGpp合成酶基因（relP）的过表达恢复了XIP对生长的抑制。我们还证明暴露于微摩尔浓度的XIP会引起UA159中(p)ppGpp积累的变化。RelA/SpoT同源酶（RSH） RelA的缺失导致(p)ppGpp积累的基础水平升高，但对XIP的敏感性降低，comR启动子活性和ComX蛋白水平降低。通过在RelA酶中引入单氨基酸取代，发现该酶的水解酶活性对XIP诱导和转化全com基因至关重要。最后，relA的缺失导致ΔrcrR突变体的表型改变，突出表现为在其他不可转化的ΔrcrR-NP突变体中恢复转化和ComX蛋白产生。因此，RelA活性及其对(p)ppGpp池的影响似乎通过RcrRPQ和rcrQ内编码的肽效应物调节能力信号传导和发育。总的来说，这项研究为突变链球菌细胞间通讯与细胞生理状态以及关键毒力相关表型调控的分子机制提供了新的见解。
The microbes that inhabit the human oral cavity are subjected to constant fluctuations in their environment. To overcome these challenges and gain a competitive advantage, oral streptococci employ numerous adaptive strategies, many of which appear to be intertwined with the development of genetic competence. Here, we demonstrate that the regulatory circuits that control development of competence in Streptococcus mutans, a primary etiological agent of human dental caries, are integrated with key stress tolerance pathways by the molecular alarmone (p)ppGpp. We first observed that the growth of a strain that does not produce (p)ppGpp (ΔrelAPQ, (p)ppGpp0) is not sensitive to growth inhibition by comX inducing peptide (XIP), unlike the wild-type strain UA159, even though XIP-dependent activation of the alternative sigma factor comX by the ComRS pathway is not impaired in the (p)ppGpp0 strain. Overexpression of a (p)ppGpp synthase gene (relP) in the (p)ppGpp0 mutant restored growth inhibition by XIP. We also demonstrate that exposure to micromolar concentrations of XIP elicited changes in (p)ppGpp accumulation in UA159. Loss of the RelA/SpoT homolog (RSH) enzyme, RelA, lead to higher basal levels of (p)ppGpp accumulation, but to decreased sensitivity to XIP and to decreases in comR promoter activity and ComX protein levels. By introducing single amino acid substitutions into the RelA enzyme, the hydrolase activity of the enzyme was shown to be crucial for full com gene induction and transformation by XIP. Finally, loss of relA resulted in phenotypic changes to ΔrcrR mutants, highlighted by restoration of transformation and ComX protein production in the otherwise non-transformable ΔrcrR-NP mutant. Thus, RelA activity and its influence on (p)ppGpp pools appears to modulate competence signaling and development through RcrRPQ and the peptide effectors encoded within rcrQ. Collectively, this study provides new insights into the molecular mechanisms that integrate intercellular communication with the physiological status of the cells and the regulation of key virulence-related phenotypes in S. mutans.