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

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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.