Bacterial Membrane Integrity under Salt and Alkaline Stress

维持pH稳定的能力对所有活细胞都是至关重要的，因为蛋白质只有在一个狭窄的最佳pH范围内才能维持其自然结构和功能。这种能力对于单细胞细菌来说尤其重要，因为与来自更复杂生物体的典型细胞相比，单细胞细菌承受的压力范围要大得多。细菌主要依靠膜转运蛋白来对抗环境ph的快速变化。然而，关于在应激条件下细胞形态如何调节以支持转运功能，我们知之甚少。基因易处理的大肠杆菌将被用作模型系统，以发展对细菌膜完整性、细胞形状和运输过程如何整合的分子理解，以及这些过程在环境变化中对细菌生存的总体影响。为了激发我们对微生物生物学基础方面的兴趣和兴趣，这些方面与我们对生理学、生态学、医学和工业的理解有关，早期本科生将在课堂和研究实验室中参与项目的几个方面。这些学生中的许多人可能属于目前在STEM学科中代表性不足的社区。为了对抗pH胁迫，细菌采用了多种策略，其中最主要的是细胞质跨膜质子转运蛋白的表达和激活，它在维持细胞质膜上的质子动力和帮助pH稳态中起着重要作用。一类转运蛋白的辅助特性是它们能够泵出许多不相关的药物并提供对杀菌剂的抗性。通常，由于高pH下钠细胞毒性的增加，以及某些细胞壁生物合成酶对pH改变的敏感性，pH胁迫与盐和细胞包膜胁迫重叠。虽然我们对细菌中pH响应的个体策略了解很多，但这些响应与盐胁迫和细胞包膜完整性的整合和重叠却知之甚少。为了解决这一差距，本研究将确定尚未表征的细胞因子参与应激反应和形态发生之间的相互作用。大肠杆菌中强大的遗传工具，结合分子、细胞生物学、生化实验和显微镜技术，将被用来定义每种蛋白质的特定功能，并确定它们如何与已知的细胞形态因子相互作用。这些研究有望增强我们对细菌细胞形态和膜完整性如何在多种应激反应中维持的理解。

The ability to maintain pH stability is critical for all living cells since proteins maintain their natural structure and function only within a narrow and optimal pH range. This ability is especially critical for single-celled bacteria that experience a far larger range of stress conditions compared to a typical cell from a more complex organism. Bacteria largely rely on membrane transport proteins to counter rapid changes in environmental pH. However, little is known about how cell morphology is modulated under stress conditions to support the transport function. The genetically tractable E. coli will be used as a model system to develop a molecular understanding of how bacterial membrane integrity, cell shape, and transport processes are integrated, and the overall impact these processes have on bacterial survival during environmental fluxes. To generate interest and excitement in fundamental aspects of microbial biology relevant to our understanding of physiology, ecology, medicine, and industry, early-stage undergraduates will be incorporated into several aspects of the project both in the classroom and in the research laboratory. Many of these students are likely to belong to communities currently underrepresented in the STEM disciplines.In order to counteract pH stress, bacteria utilize multiple strategies, chief among which is the expression and activation of cytoplasmic membrane-spanning proton transporters, which play essential roles in the maintenance of proton motive force across the cytoplasmic membrane and aid in pH homeostasis. An auxiliary property of a class of these transporters is their ability to pump out numerous unrelated drugs and provide resistance to biocides. Often, pH stresses overlap with salt and cell envelope stresses due to the increase in sodium cytotoxicity at high pH, and the susceptibility of certain cell wall biosynthetic enzymes to altered pH. While much is known about individual strategies of pH responses in bacteria, the integration and overlap of these responses with salt stress and cell envelope integrity, is poorly understood. To address this gap, this research will identify as yet uncharacterized cellular factors involved in the interplay between stress responses and morphogenesis. The repertoire of powerful genetic tools in E. coli in combination with molecular, cell biological, biochemical experiments, and microscopy techniques, will be exploited to define the specific function of each protein, and determine how they interact with known cell morphology factors. These studies are expected to enhance our understanding of how bacterial cell morphology and membrane integrity are maintained in response to multiple stresses.