Incollection,
Optimality and Robustness in Bacterial Growth Control
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
In order to grow at the highest rate sustainable by the
environment, bacteria turn on different metabolic pathways and
utilize a myriad of adaptive strategies. The macromolecular
composition (RNA, DNA, protein) and overall cell size (mass) can be
very different in different environments. Surprisingly however,
these differences appear to depend only on the growth rate and not
on the growth medium itself. As the nutritional environment changes
in time, the cells quickly adapt their composition to the one
corresponding to the new conditions. Here, we propose a
phenomenological model of growth and adaptation control for the
bacterial cell, based on a simplified formulation of the central
dogma and a simplified implementation of the stringent response
which controls ribosome synthesis. Applied to growth limitation by
amino acid starvation, the model suggests a spectacular mechanism
by which the cell can synthesize just the necessary amount of
ribosomes to maintain optimal growth, in a way that is insensitive
(i.e., robust) to the specific form of the stringent response or
the particulars of the nutrient source or influx rate. The
phenomenological model further predicts rapid recovery and damped
oscillation upon changes in growth due to medium shifts.
