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Non-invasive determination of bacterial single cell properties by electrorotation
1Institut für Biophysik, Freie Universität Berlin, Thielallee 63, D-14195, Berlin, Germany. ralphbph@zedat.fu-berlin.de
Biochimica Et Biophysica Acta
|May 8, 1999
Summary
This study presents a novel electrorotation system for analyzing single bacterial cells, enabling the determination of their physical properties in vivo. This breakthrough extends cell analysis capabilities to bacteria, previously limited to eukaryotes.
Area of Science:
- Biophysics
- Microbiology
- Cell Biology
Background:
- Electrorotation is a powerful technique for characterizing single cell properties.
- Previous applications of electrorotation were limited to eukaryotic cells.
- Bacterial cells present unique challenges for electrorotation due to their small size and movement.
Purpose of the Study:
- To develop an experimental system for recording electrorotation spectra of single bacterial cells.
- To enable in vivo determination of physical properties of bacterial cell components.
- To extend the application of electrorotation to prokaryotic organisms.
Main Methods:
- Development of a micro-scale measuring chamber for electrorotation.
- Utilized single-frame video analysis for microscopic observation of bacterial rotation.
- Applied a three-shell model for evaluating experimental electrorotation data.
- Investigated bacterial cells (E. coli) across a frequency range of 1 kHz to 1 GHz.
Main Results:
- Successfully recorded electrorotation spectra of single bacterial cells.
- Determined electrical conductivities of cytoplasm (4.4 mS/cm) and outer membrane (25 microS/cm).
- Found periplasmic space conductivity increases with the square root of medium ionic strength.
- Measured specific capacitances of inner (1.4 microF/cm2) and outer membranes (0.26 microF/cm2), and periplasm thickness (~50 nm).
- Observed reduced cytoplasmic conductivity (0.9 mS/cm) after heat treatment, suggesting ion efflux.
Conclusions:
- The developed system enables electrorotation analysis of single bacterial cells.
- Physical properties of bacterial cell compartments can be determined in vivo.
- This method provides new insights into bacterial cell electrophysiology and membrane properties.
