Christoph Schmidt
Duke University

Editor, Cell Biophysics
Biophysical Journal
 

What are you currently working on that excites you?

We are currently trying to understand how mechanosensitive channels in bacteria work. These channels are the emergency pressure-release valves that bacteria need to survive sudden shocks in their environmental conditions, for example, when they transit from the guts of an animal into the water of a lake. These channels are far less well understood than I first thought. They are believed to be opened when the mechanical tension in the inner cell membrane reaches a certain threshold. But how is this tension divided between the lipid cell membrane and the tough protective polymer network surrounding the lipid membrane? Why do bacteria need thousands of copies of channels while two or three would be enough to release pressure? We use atomic force microscopy to mechanically manipulate bacteria and can observe how the channels open and release a little bit of the cell’s contents every time they open. This research also has implications for the development of new antibiotics, because many antibiotics attack the bacterial cell wall, and we need to know how defects in the wall develop and what the bacteria are doing to fix them. 

What has been your most exciting discovery as a biophysicist?

Back when I was a postdoc, working with Steve Block at the Rowland Institute in Cambridge, Massachusetts, we set out to observe single motor protein molecules at work by using a laser beam forming so-called “optical tweezers.” We worked hard on both the protein preparation and the custom-built instrument. After many months of labor, solving a million problems, we finally had little glass beads with just one or two kinesin motor proteins attached to them in such a way that they could actually do their job and move along microtubules, protein polymers that are part of the cell cytoskeleton. We recorded the trajectories of the beads with nanometer resolution. Nobody could talk in the room during the experiment because it would spoil the signal. Then we saw, for the first time, how a single motor moved its bead in tiny little steps of 8-nm size, creating a staircase trajectory. Seeing this appearing on the computer screen was incredibly exciting.