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Plasmolysis and cell shape depend on solute outer-membrane permeability during hyperosmotic shock in E. coli
Teuta Pilizota1, Joshua W Shaevitz
1Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, USA.
Biophysical Journal
|June 25, 2013
Summary
Bacterial cells like Escherichia coli respond to osmotic shock by changing shape. The type of solute used determines whether cells shrink uniformly or undergo plasmolysis, offering insights into cell envelope mechanics.
Area of Science:
- Microbiology
- Cell Biology
- Biophysics
Background:
- Bacterial turgor pressure is vital for cell growth and survival.
- Hyperosmotic shock in Escherichia coli causes cell envelope pressure drops, leading to shape changes like plasmolysis.
- Previous studies reported conflicting results on bacterial responses to osmotic shock.
Purpose of the Study:
- To investigate the dynamic response of single Escherichia coli cells to hyperosmotic shock.
- To differentiate cellular responses based on solute permeability across the cell envelope.
- To quantify morphological changes during osmotic shock under various conditions.
Main Methods:
- Single-cell fluorescence imaging with high temporal resolution (seconds).
- Application of hyperosmotic shock using solutes with varying membrane permeability (impermeable, rapidly permeable ions, slowly permeable sucrose).
- Quantitative analysis of cell volume, shape, and membrane dynamics.
Main Results:
- Outer-membrane impermeable solutes caused cell volume reduction without plasmolysis.
- Rapidly permeable ions induced immediate plasmolysis.
- Slowly permeable solutes like sucrose led to gradual plasmolysis as chemical potential equilibrated.
- Non-plasmolyzed cells shrank in length and width; plasmolyzed cells showed pole shrinkage or invagination along the cylinder.
Conclusions:
- The permeability of solutes dictates the immediate response of Escherichia coli to hyperosmotic shock.
- Cellular morphological changes during shock depend on the rate of osmotic equilibration.
- This study reconciles previous conflicting findings by detailing the dynamics of osmotic shock response.
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