Lecturer: Prof. Ned S. Wingreen
Affiliation: Princeton University
Abstract:
The chemotaxis network of bacteria such
as E. coli is remarkable for its sensitivity
to minute relative changes in chemical
concentrations in the environment. Much
of this acute sensitivity can be traced to
the collective behavior of teams of
chemoreceptors on the cell surface.
Coupled with a system for adaptation, the
advantage for chemotaxis is gain – i.e.,
small relative changes in chemical
concentrations are transduced into large
relative changes in signaling activity.
However, something is troubling about
this simple explanation: in addition to
providing gain, the coupling of receptors
into teams also increases noise, and the
net result is a decrease in the signal-to-
noise ratio of the network. Why then are
chemoreceptors observed to form
cooperative teams? I will present a novel
hypothesis that the run-and-tumble
chemotactic strategy of bacteria leads to
a “noise threshold”, below which noise
does not significantly decrease
chemotactic velocity, but above which
noise dramatically decreases this
velocity.