Pushkar P. Lele's talk

Mar 02, 2017 - 17:00

Mar 02, 2017 - 18:00

Rm. No. 118 Ground floor Chemical Engg. Dept.

Seminars

Pushkar P. Lele Department of Chemical Engineering Texas A&M University USA

Abstract: The ability to mechanically-sense solid surfaces is important for motile bacteria to initiate swarming – a rapid surface-dependent group-motility associated with infections. Such mechanical sensing (mechanosensing) involves the bacterial flagella but the mechanisms remain poorly understood. I will discuss our recent work that combined single-molecule imaging fluorescencerecovery-after-photobleaching and optical tweezers to determine how single flagellar motors (that rotate the flagellum) sense mechanical signals in live cells. I will explain how the motor regulates its assemblies in response to mechanical stimulus with a simple model that incorporates a catch-bond mechanism. Additionally a molecular switch within the motor that is responsible for changes in the direction of rotation also responds to mechanical stimuli by adapting its activity. The amount of torque generated by the motor depends on the switch – torque is higher in the CCW direction and lower in the CW direction. Yet cells that carry a single rigid flagellum swim with similar speeds in the forward and backward directions. The resulting paradox that emerges due to the time-reversibility of Stokes flow can be resolved with a simple model that incorporates cell-precession during swimming. I will conclude with a brief note on the relevance of these findings to our current understanding of the influence of mechanical forces on signaling and the evolutionarily-conserved motor-mechanics.Biosketch: Dr. Pushkar Lele joined as an assistant professor at the Department of Chemical Engineering Texas A&M in 2015. He completed his postdoctoral training in Professor Howard Berg’s Biophysics laboratory at Harvard University. He received his PhD in Chemical Engineering from the University of Delaware in experimental soft-matter physics. Dr. Lele’s current research interests are in bacterial biophysics with a focus on cell mechanics motility and intracellular signaling. His group employs a variety of techniques including protein engineering microfluidics force-spectroscopy single molecule fluorescence and computational modeling. Dr. Lele’s recent findings on molecular motor physics have been published in Science Advances PNAS Current Biology and Nature Physics. (Compulsory for CL702 and CL704 students)