[printer friendly version]

AMO/QO PIZZA SEMINAR


"Bacterial Flagella: Motor Mechanics and Motility"


Dr. Pushkar P. Lele
Chemical Engineering, Texas A&M University

ABSTRACT 

The ability to mechanically sense solid surfaces is important for motile bacteria to initiate swarming - a rapid surface-associated group motility. Such mechanical sensing (mechanosensing) involves the bacterial flagella. Although swarms are known to play a role in infections and antibiotic resistance, the signaling mechanisms responsible for the initiation of swarming remain poorly understood.

I will discuss our recent work that combined single-molecule imaging, fluorescence-recovery-after-photobleaching and optical tweezers to determine how the flagellar motor senses mechanical signals. I will present data that provides evidence that the chemotactic output of a molecular switch within the motor is influenced by the response to perturbations in viscous loads. The switch changes the direction of motorrotation and the torque generated is anisotropic. Yet, Caulobacter Crescentus cells that carry a single rigid flagellum, unlike E. coli cells that carry many, swim with similar speeds in the forward and backward directions. The resulting paradox that arises due to the time-reversibility of Stokes flow can be resolved with a simple model that incorporates cell-precession during swimming. Our observations indicate that motor mechanics are similar between the two species belonging to different classes of bacteria, and suggest that motor-mechanosensing might also be conserved. I will conclude with a note on the relevance of these findings to our current understanding of the mechanisms of cell-adaptability and swarm-initiation.



Wednesday, September 21, 2016
IQSE 578, 12:30 Noon
Mitchell Physics Building


Institute for Quantum Science and Engineering
Texas A&M University

(Pizza, salad, and soda to be served at 12:00 noon)