Bacterial osmoadaptation: coordination of osmoregulatory systems and their roles in cell growth

渗透压的变化导致水流过包裹活细胞的膜。这样的水通量会扰乱细胞的结构和功能。细胞通过调整其被称为有机渗透物质(氨基酸、糖等)的物质的含量来做出反应。这种“渗透调节”控制水流，以确保细胞保持适当的水分，稳定它们的内部结构，并支持它们的持续生长。已经描述了调节细菌渗透调节物质含量的渗透调节机制。现在我们的目标是了解大肠杆菌的渗透调节系统是如何协调的。我们将检验以下假设。首先，ProQ蛋白是一种RNA伴侣蛋白，它调节渗透压调节蛋白的编码基因，包括prop和prou。其次，在大肠杆菌细胞的末端，道具与其他以膜为基础的渗透调节蛋白聚集在一起，呈杆状。这种蛋白质聚集是细胞膜和“细胞骨架”成分之间特定相互作用的结果，对于有效的渗透调节和细胞生长是必要的。 这项研究旨在解决基本的生物学问题。除了阐明渗透调节机制外，它还可能向我们展示细菌细胞结构是如何形成和功能的。它教我们如何完全翻译基因组，预测编码的RNA和蛋白质的结构和功能。它可能会向我们展示小RNA是如何控制基因表达的。一些大肠杆菌菌株可促进其人类和动物宿主的健康。其他菌株在感染肠道、大脑、膀胱或肾脏时会导致疾病。尽管我们的工作不是为了直接解决食品或水安全问题，也不是为了控制疾病，但它将展示渗透调节机制如何帮助大肠杆菌在食物、水和动物(包括人)中生存。我们的发现也将适用于必须耐受渗透压力变化的其他微生物、动植物的细胞。它们包括酵母(用于制造面包、啤酒和葡萄酒)、植物根和叶细胞(耐干旱和盐碱地)以及肾细胞(控制人和动物的水合作用)。

Osmotic pressure changes cause water to flow across the membranes that encase living cells. Such water fluxes can perturb cell structures and functions. Cells respond by adjusting their content of substances called organic osmolytes (amino acids, sugars etc). This "osmoregulation" controls water flow to ensure that cells remain properly hydrated, to stabilize their internal machinery, and to support their continuing growth. The osmoregulatory machinery that modulates bacterial osmolyte content has been described. Now we aim to learn how the osmoregulatory systems of bacterium Escherichia coli are coordinated. We will test the following hypotheses. First, the ProQ protein is an RNA chaperone that regulates the genes encoding osmoregulatory proteins, including ProP and ProU. Second, ProP clusters with other membrane-based osmoregulatory proteins at the ends of E. coli cells, which are rod-shaped. This protein clustering, resulting from specific interactions among cell membrane and "cell skeleton" components, is necessary for effective osmoregulation and cell growth. This research is designed to address fundamental biological questions. In addition to elucidating osmoregulatory mechanisms it may show us how bacterial cell structures form and function. It is teaching us how to fully translate genomes, predicting the structures and functions of the encoded RNAs and proteins. It may show us how small RNAs control gene expression. Some E. coli strains promote the health of their human and animal hosts. Other strains cause diseases when they infect intestines, brains, bladders or kidneys. Although our work is not designed to directly address food or water safety problems, or control disease, it will show how osmoregulatory mechanisms help E. coli to survive in food, water and animals, including people. Our discoveries will also apply to cells of other microbes, animals and plants that must tolerate osmotic pressure changes. They include yeasts (used to make bread, beer and wine), plant root and leaf cells (which tolerate drought and saline soils) and kidney cells (which control the hydration of people and animals).