Download
slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
The Dependence of Bacterial Cell Growth on Turgor Pressure PowerPoint Presentation
Download Presentation
The Dependence of Bacterial Cell Growth on Turgor Pressure

The Dependence of Bacterial Cell Growth on Turgor Pressure

129 Views Download Presentation
Download Presentation

The Dependence of Bacterial Cell Growth on Turgor Pressure

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  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 osmotic pressure within bacteria is much higher than atmospheric pressure. Morse Equation Gram negatives: P ~ 1 atm Gram positives: P ~ 10 atm

  4. The bacterial cell wall is a cross-linked polymeric gel that encloses the cell. Polysaccharides Polypeptides Gan et al., 2008 Bacillus

  5. Mechanical stress the in cell wall balances the turgor pressure and stretches the wall. ε = strain =Δl/le Bacillus - w/Gaurav Does stress also determine strain rate of the cell wall, i.e., growth rate of the cell?

  6. This growth in size of the cells appears to be the result of the progressive effect of endosmosis. They distend under the influence of the liquid, and gradually expand like soap bubbles expand under the influence of air which distends them. Cell walls themselves are composed of molecules, and also experience development, particularly the trend of expansion.

  7. Ball-and-Spring Model of the Cell Wall χ Cross-Link Conc. ξ Mesh Size Spring Constant Rate of Cross-Link Dissociation Strain Rate Rojas, et al. 2011

  8. Ball-and-Spring Simulation Platform Jen Hsin Furchtgott et al., 2011

  9. B. mycoides

  10. Growth rate depends on the osmolarity of the medium. Growth rate vs. medium osmolarity of Salmonella in different media Conc. of Sucrose or Salt  Scott, 1953; Christian and Scott 1955

  11. Christian, 1955

  12. Measures, 1975

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

  14. Characterizing the response of cells to changes in osmolarity

  15. Single cell measurements Dye tracing concentration of mannitol in LB

  16. Raw Data: length vs. time T=30 s

  17. Strain rate vs. time n=32

  18. Turgor pressure modulates growth rate T=30 s

  19. The frequency-dependent waveform response of growth rate elucidates the time scale of osmoregulation

  20. The phase is constant across a range of driving frequencies

  21. A simple model I. Constitutive Equation { { Elasticity Growth II. Morse Equation III. Osmoregulation

  22. A simple solution I. II. III.

  23. Data Model

  24. Things to do: test and refine the model ? amplitude ω • Ion channel knockouts • Deprive cells of compatible solutes • Knockout/over-express/purify endopeptidase

  25. To do: comparative study B. subtilis

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

  27. Things to do: apply external mechanical force Optical Trap – w/Tim Squashed Cells - Kian • Other ideas: • Functionalized microcapillary • MEMS device

  28. Thanks!