The Dependence of Bacterial Growth Rate on Osmotic
The Dependence of Bacterial Growth Rate on Osmotic Pressure Rico Rojas
“Ever since I was a child I have had this instinctive urge for expansion and growth, ” - Bruce Lee
Goal: To measure and understand if and how bacterial cell growth depends on osmotic pressure. Vibrio
Terminology Elastic Strain Growth Rate (Strain Rate)
Raw Data: length vs. time T=30 s
Strain rate vs. time n=32 v
Turgor pressure modulates growth rate T=30 s v(s-1)
Questioned that remained: 1) Are we really changing the turgor pressure? 2) To what extent are the oscillations in “growth rate” we observe simply elastic deformation?
Tracking WGA-stained E. coli
1) Are we really changing the turgor pressure?
Is the response purely elastic? Well, if the oscillations are purely elastic: 1) The growth rate during the periods of high osmolarity should be the same as that during low osmolarity. In addition, the growth rate averaged over the periods during which the media is switching should be equal to this value. 2) Amplitude of oscillation in length should not depend on the driving frequency.
100 m. M 200 m. M
Conclusions: Honest-to-goodness growth, not just elastic deformation is correlated with osmotic pressure. To do: 1) Flesh out the data 2) Figure out the mechanism/start doing some math.
- Slides: 24