Dr. Yann Dufour

October 31, 2016

Title: Performance trade-off in bacterial chemotaxis reveals constraints on integral feedback control.

Speaker: Yann Dufour, Department: Microbiology and Molecular Genetics, MSU

Abstract:Successful navigation by simple organisms, such as bacteria, relies on proper coupling between sensors, which gather information during motion, and actuators, which control the behavioral response. Because behavior determines input signals, behavioral feedback can place sensors and actuators in an operational regime that is difficult to optimize. In bacterial chemotaxis, robust performance is often attributed to the zero integral feedback control of the sensor, which guarantees that activity returns to resting state when the input remains constant. While this property provides sensitivity over a wide range of signal intensities, other parameters such as adaptation rate and basal activity affect chemotactic performance. By modeling how sensory information carried by the chemotaxis response regulator is best utilized by the flagellar motors, we identify an operational regime that maximizes drift velocity along chemical concentration gradients for a wide range of environments. We found that as the strength of the feedback increases individual cells cannot maintain the optimal operational regime in all environments, suggesting that phenotypic diversity generated by stochastic fluctuations in protein expression may be beneficial as a bet-hedging strategy for clonal populations.