Title: Optimal Strategies in Single Cell Sensing & Response
Speaker: Dr. Sima Setayeshgar
Institute: Indiana University
Description: Biochemical reactions constitute the cell's computing language, carrying out the processes of life from cell growth and death to response to environmental cues. In a classic work, Berg and Purcell showed that bacterial chemo taxis,where a single-celled organism responds to small changes in the concentration of chemicals outside the cell, is limited directly by molecule counting noise and that aspects of the bacteria's computational and behavioral strategies are optimal given the physical constraints. In this talk, I will revisit and extend their arguments: For the ubiquitous case of sensing by multiple, cooperatively interacting biological receptors, I will show that while the sensitivity of response to the change in concentration of signaling molecules is enhanced, the accuracy is limited by the irreducible noise related to the random arrival of diffusing molecules. I will compare theoretical limits with quantitative experimental results for the cooperative bacterial flagellar motor demonstrating performance consistent with physical limits. I will also discuss related work aimed at understanding system-level properties of the chemo taxissign aling network from the standpoint of network adaptation and information transmission.