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October 4, 202211:30 am (CDT)

AMO/IQSE seminar: The bacterial sense of touch: how micron-small cells measure substrate mechanics using molecular-scale fingers


Matthias Koch (Department of Biology, Texas A&M University)





Texas A&M University, Department of Physics and Astronomy, MPHY 578 / IQSE Seminar Room

College Station

About The Speaker

Matthias Koch is an Assistant Professor of Biology at Texas A&M University. He uses biophysical tools and light microscopy approaches to understand how bacteria sense and interact with their physical environment. Matthias received his undergraduate and master’s degrees in Physics from the University of Freiburg, Germany. He consequently joined the Department of Microsystems Engineering at the University of Freiburg to receive a PhD with distinction in biophysics. His work developing new optical tweezers and microscopy approaches to study the mechanics of helical bacteria and momentum transport through artificial cytoskeletal networks was recognized with the Wolfgang Gentner Early Career Award. During his Postdoc in the Departments of Physics, Molecular Biology, and Genomics at Princeton, he discovered that despite their miniature size, bacteria have a sense of touch similar to humans and can distinguish substrates by their mechanical stiffness. After joining Texas A&M in 2022, his lab uses multidisciplinary approaches leveraging the arsenal of genetic and molecular tools, advanced super-resolution and force probing microscopy techniques, as well as biophysical modeling and computer simulations, to understand the fundamental biophysical principles of stiffness sensing and of the molecular machine that drives this remarkable feature.

Event Details

Host colonization by commensal or pathogenic bacteria has traditionally been studied in terms of the chemical and biological factors associated with the environment. Although the mechanical environment of a cell can vary tremendously and can be as rigid as bone or as soft as mucus, it has not gained much attention as a determinant of bacterial infections. Here, I will show that the clinically important pathogen Pseudomonas aeruginosa distinguishes substrates by their stiffness and tunes over 100 virulence related genes to substrate rigidity. These results suggest that P. aeruginosa can distinguish its broad spectrum of infection sites by substrate mechanics and modulate virulence factors specifically to each site. Specifically, I will explain how stiffness sensing is facilitated by a fascinating nanomachine: the type IV pilus (TFP). TFP are large membrane-spanning complexes that use two dedicated molecular motors for quickly extending and retracting of a micrometer-long polymeric fiber (the pilus) to the environment. Combining different experimental biophysical tools, mathematical modeling, and numerical simulations, I will show how TFP retraction deforms the substrate and is used to measure its rigidity much like molecular-scale human fingers squeezing a fruit to check its ripeness. I will further explain how the two motors of TFP are coordinated biophysically to generate the observed cycles of extension and retraction that ultimately facilitate stiffness sensing.

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