Thread by @PetraLevin

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

biorxiv.org/content/10.110…

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

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

pnas.org/content/pnas/1…

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
proteopedia.org/wiki/images/3/…

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

frontiersin.org/articles/10.33…

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

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.

As with much of the work in my group, undergraduates from @WUSTLBio and @KenyonCollege were critical to the success of this project!