Regulation of osmolyte synthesis in the moderate halophile Halobacillus halophilus

中度嗜盐、依赖氯的嗜盐细菌嗜盐杆菌通过胞内产生摩尔浓度的相容溶质来应对环境中的盐度。有趣的是，它将其渗透调节策略从中等浓度的谷氨酸/谷氨酰胺转变为高盐度下的脯氨酸，我们已经获得了参与盐度感知的两步过程的证据，氯离子和谷氨酸是关键角色。在这里，我们将讨论使用亚细胞系统感知和响应盐度变化的分子基础。整个细胞的谷氨酰胺合成酶活性被鉴定为氯和盐的感受器，并鉴定和纯化了负责的酶(GlnA2)。我们将通过生化、生物物理、分子和遗传工具分析纯化的GlnA2来解决感知和激活的模式。此外，还鉴定了与盐度相关的脯氨酸生物合成相关的基因，发现谷氨酸在很大程度上刺激了这些基因的表达。在项目的第二部分，我们将重点研究谷氨酸激活的基因表达的机制。此外，还将研究脯氨酸生物合成蛋白的产生及其酶活性的调节。

The moderately halophilic, chloride-dependent bacterium Halobacillus halophilus copes with the salinity in its environment by the intracellular production of compatible solutes in molar concentrations. Interestingly, it switches its osmolyte strategy from glutamate/glutamine at moderate to proline at high salinities and we have obtained evidence for a two-step process involved in sensing salinity with chloride and glutamate as key players. Here, we will address the molecular basis of sensing and responding to changing salinities using subcellular systems. The glutamine synthetase activity in whole cells was characterized as a chloride and salt sensor and the responsible enzyme (GlnA2) was identified and purified. We will address the mode of sensing and activation by analyzing purified GlnA2 with biochemical, biophysical, molecular and genetic tools. The genes involved in salinity-dependent proline biosynthesis were also identified and their expression was shown to be stimulated to a great extent by glutamate. In the second part of the project we will focus on the mechanism of glutamate-activated gene expression. Furthermore, the regulation of production of proline biosynthetic proteins as well as their enzymatic activity will be studied.