the dependence of bacterial cell growth on turgor pressure
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
Outer membrane
Cell wallInner membrane Polysaccharides Polypeptides
Gan et al., 2008
Caulobacter
Micrasterias
PhycomycesAcetabularia
Stella
The cell wall defines a cell’s shape.
Cell Wall Expansion = Cell growth
Cell Shape
Cell Function
ReproductionHelicobacter
Caulobacter
Cell wall expansion is equivalent to cell growth.
The hydraulic pressure within cells, called the turgor pressure, is much higher than atmospheric pressure.
Gram negatives: ΔP ~ 1 atmGram positives: ΔP ~ 10 atm
Huang et al., 2008
Mechanical stress the in cell wall balances the turgor pressure and stretches the wall.
Growth of the cell wall requires two processes:1) Dissipation of elastic energy, i.e. irreversible deformation2) Addition of new material to the existing wall
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.
Furchtgott et al., 2011t
Bacteria have a number of mechanisms for regulating their turgor.
Wood, 2006
Biological materials have complex mechanical properties.
Koenderink et al., 2006
Gile, et al.
Actin microrheology
Characterizing the response of cells to changes in osmolarity – the “Cell Rheometer.”
Single cell measurements
Turgor Pressure Modulates Growth Rate.
Things to do this year: construct a model
€
˙ ε ~ kP ~ k(Cin − Cout )
€
˙ C in ~ f (Cin ,Cout ) − g(P)
Growth Rate
X-linkdissociation
Pressure Conc. of solutes
Solute Uptake
Solute Release
Things to do: test the model
1. Ion channel knockouts2. Deprive cells of compatible solutes3. Knockout/over-express/purify endopeptidase4. Compare different morphologies, species,
kingdoms
Things to do: apply external mechanical force
Other ideas:1. Functionalized microcapillary2. MEMS device
Optical Trap
Squashed Cells
Things to do: address the relationship between synthesis and mechanics
Garner et al., 2011
MreB Motion
Thanks!