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Fluorescence measurement of intracellular sodium concentration in single Escherichia coli cells

Research output: Contribution to journalArticle

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Publication details

JournalBiophysical Journal
DatePublished - 1 Jan 2006
Issue number1
Number of pages9
Pages (from-to)357-365
Original languageEnglish


The energy-transducing cytoplasmic membrane of bacteria contains pumps and antiports maintaining the membrane potential and ion gradients. We have developed a method for rapid, single-cell measurement of the internal sodium concentration ([Na(+)](in)) in Escherichia coli using the sodium ion fluorescence indicator, Sodium Green. The bacterial flagellar motor is a molecular machine that couples the transmembrane flow of ions, either protons (H(+)) or sodium ions (Na(+)), to flagellar rotation. We used an E. coli strain containing a chimeric flagellar motor with H(+)- and Na(+)-driven components that functions as a sodium motor. Changing external sodium concentration ([Na(+)](ex)) in the range 1-85 mM resulted in changes in [Na(+)](in) between 5-14 mM, indicating a partial homeostasis of internal sodium concentration. There were significant intercell variations in the relationship between [Na(+)](in) and [Na(+)](ex), and the internal sodium concentration in cells not expressing chimeric flagellar motors was 2-3 times lower, indicating that the sodium flux through these motors is a significant fraction of the total sodium flux into the cell.

    Research areas

  • Bacterial Outer Membrane Proteins, Bacterial Proteins, Calibration, Carbonyl Cyanide m-Chlorophenyl Hydrazone, Cell Membrane, Cytoplasm, Dose-Response Relationship, Drug, Escherichia coli, Fluorescent Dyes, Gramicidin, Light, Microscopy, Fluorescence, Organic Chemicals, Photobleaching, Plasmids, Protons, Sodium, Time Factors

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