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The Dependence of Bacterial Cell Growth on Turgor Pressure

The Dependence of Bacterial Cell Growth on Turgor Pressure. Rico Rojas. Goal: To measure and understand how expansion of the bacterial cell wall depends on mechanical force. Vibrio. The bacterial cell wall is a cross-linked polymeric gel that encloses the cell. S-Layer.

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The Dependence of Bacterial Cell Growth on Turgor Pressure

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  1. The Dependence of Bacterial Cell Growth on Turgor Pressure Rico Rojas

  2. Goal: To measure and understand how expansion of the bacterial cell wall depends on mechanical force. Vibrio

  3. The bacterial cell wall is a cross-linked polymeric gel that encloses the cell. S-Layer Outer membrane Cell wall Polysaccharides Polypeptides Inner membrane Caulobacter Gan et al., 2008

  4. The cell wall defines a cell’s shape. Stella Micrasterias Phycomyces Acetabularia

  5. Cell wall expansion is equivalent to cell growth. Cell Wall Expansion = Cell growth Reproduction Cell Shape Helicobacter Cell Function Caulobacter

  6. The hydraulic pressure within cells, called the turgor pressure, is much higher than atmospheric pressure. Gram negatives: ΔP ~ 1 atm Gram positives: ΔP ~ 10 atm Huang et al., 2008

  7. Mechanical stress the in cell wall balances the turgor pressure and stretches the wall.

  8. Growth of the cell wall requires two processes: Dissipation of elastic energy, i.e. irreversible deformation Addition of new material to the existing wall t Furchtgott et al., 2011 In theory, the rate of irreversible deformation (or “growth”) depends on the mechanical stress in the cell wall, and therefore on the turgor pressure. See Gaurav’s and Jen’s talks.

  9. Bacteria have a number of mechanisms for regulating their turgor. Wood, 2006

  10. Biological materials have complex mechanical properties. Actinmicrorheology Gile, et al. Koenderink et al., 2006

  11. Characterizing the response of cells to changes in osmolarity – the “Cell Rheometer.”

  12. Single cell measurements

  13. Turgor Pressure Modulates Growth Rate.

  14. Things to do this year: construct a model X-link dissociation Growth Rate Conc. of solutes Pressure Solute Uptake Solute Release

  15. Things to do: test the model • Ion channel knockouts • Deprive cells of compatible solutes • Knockout/over-express/purify endopeptidase • Compare different morphologies, species, kingdoms

  16. Things to do: apply external mechanical force Squashed Cells Optical Trap • Other ideas: • Functionalized microcapillary • MEMS device

  17. Things to do: address the relationship between synthesis and mechanics MreB Motion Garner et al., 2011

  18. Thanks!

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