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Starving E. coli, serendipitous discoveries, and awesome collaborators: a long thread 
on some of our latest work with @handuo_s and KC Huang @StanfordBioE 1/19 https://www.biorxiv.org/content/10.1101/2020.12.06.413849v2
on some of our latest work with @handuo_s and KC Huang @StanfordBioE 1/19 https://www.biorxiv.org/content/10.1101/2020.12.06.413849v2
To help understand the relationship between the environment & cell growth, PD Corey Westfall & undergraduates Jesse Kao, Montana Sievert, & Jeremy Moore plucked E. coli from cozy carbon rich medium, rinsed, rinsed, rinsed & resuspended in minimal salts. And got a surprise... 2/19
E. coli SHRANK! 3/19
E. coli anatomy is important for this story, so a brief digression.
E. coli’s cell envelope has three layers: a plasma membrane, a thin cell wall, and its semipermeable outer membrane. 4/19
E. coli’s cell envelope has three layers: a plasma membrane, a thin cell wall, and its semipermeable outer membrane. 4/19
A closer look at the starved cells revealed that their plasma membrane and cytoplasm had SHRUNK away from the cell wall and outer membrane! 5/19
About this time I went to the always fantastic Conference on Prokaryotic Cell Biology and Development and saw this image from KC Huang. It definitely got my attention! 6/19
Rather than starved, KC’s cells were deficient in the machinery that maintains homeostasis between the inner and outer membranes. 7/19
https://www.pnas.org/content/pnas/113/11/E1565.full.pdf
https://www.pnas.org/content/pnas/113/11/E1565.full.pdf
KC and I decided to team up and figure this out! 5 years later with contributions from the awesome @handuo_s we’ve learned a ton. First, starvation is key. Handuo even discovered stationary phase cells shrink (red=fluorescent periplasmic marker) #hiddeninplainsight! 8/19
Second, when the cytoplasm shrinks it becomes more dense 9/19
Third, shrinkage in exponentially growing cells is almost exclusively at the NEW pole #Ilovethisexperiment 10/19
Fourth, shrinkage is independent of biosynthesis and pretty much every stress response pathway we looked at. 11/19
Fifth, recovery is dependent on metabolism 12/19
Sixth, recovery requires a functional link between the plasma membrane and outer membrane, mediated by the Tol/Pal system. 13/19
https://proteopedia.org/wiki/images/3/31/TOL.jpg
https://proteopedia.org/wiki/images/3/31/TOL.jpg
Deletion of Tol/Pal makes recovering cells very very very unhappy 14/19
We think Tol/Pal helps “zip” the plasma membrane back into its cell wall and outer membrane “coat” 15/19
So what is going on? Our best guess is that PM retraction is a passive but generally positive response to nutrient stress. 16/19
Super-cool is that E. coli is not the only bacterium to do this. Klebsiella also retracts & @BriegelAriane has beautiful data indicating viable but non-culturable Vibrio cholerae also shrink their cytoplasm. 17/19
https://www.frontiersin.org/articles/10.3389/fmicb.2019.00793/full
https://www.frontiersin.org/articles/10.3389/fmicb.2019.00793/full
We still have questions!
1. Is shrinking a physical-chemical consequence of starvation?
2. Is shrinking regulated?
3. Does shrinking confer any advantages?
4. Are shrunken cells metabolically active?
5. What is relationship between shrinkage & membrane homeostasis?
18/19
1. Is shrinking a physical-chemical consequence of starvation?
2. Is shrinking regulated?
3. Does shrinking confer any advantages?
4. Are shrunken cells metabolically active?
5. What is relationship between shrinkage & membrane homeostasis?
18/19
Finally, this had been a fantastically fun project and wonderful example of the power of collaborative science. We would love to know if anyone has seen similar phenomena! 19/19
Like all good science, this work would not have been possible without the hard work of a bunch of wonderful people including Pascal D. Odermatt, Spencer Cesar, Sarah Anderson, Carlos G. Gonzalez, Lichao Zhang and Joshua E. Elias and the always fabulous Professor Fred Chang.
