Joshua W. Shaevitz

The cells that make up all living organisms come in a dizzying array of sizes and shapes, each with unique structural and mechanical properties. When many cells move they contort their bodies to glide along surfaces or swim through fluid. We are interested in the different physical strategies that mother nature has found to create the cellular and sub-cellular structures that perform these amazing feats.

One of the species we study, Spiroplasma melliferum, is a helix barely more than 100 nm across and a few microns long. How does this cell achieve its beautiful shape? When these cells swim they change the helicity of their entire bodies to produce movement. How does this work? How can a cell organize its contents in such a tightly packed space?

It was recently discovered that many, if not all, bacteria use an internal cytoskelton to define their shape, to guide intracellular organization and to produce movement. Our lab studies physical aspects of the prokaryotic cytoskeleton. What are the structural properties of the individual cytoskeletal filaments and how do they contribute to overall cell mechanics? Is mechanical stress induced by the cytoskeleton used to determine cell shape? Are these filaments used as tracks by molecular motors as they are in eukaryotes by kinesin and myosin? These are just some of the basic questions that our lab is interested in.

For this research, we are developing new instrumentation that combines mechanical perturbation of cells and molecules with visualization of key protein and macromolecular structures. Our toolbox includes unique combinations of optical microscopy, fluorescence and deconvolution microscopy, optical trapping, atomic force microscopy, as well as biophysical modeling and simulation.