Robert Planqué: Maximising microbial growth rate in changing environments

Microbes such as bacteria and yeasts actively optimise their cellular growth rate by tuning concentrations of catalytic enzymes and ribosomes. They are able to switch metabolism to accomodate changes in food substrates, mount stress responses, and even shut down the entire cell and go in growth arrest when the need arises. In this talk I will present a general framework in which the allocation of enzymes and ribosomes necessary for cellular metabolism are adapted to steer the system to optimal steady state growth rate. I will first introduce a basic unit of microbial metabolism, called Elementary Growth Modes.
EGMs provide a classification of possible self-replication strategies available to cells, given their genotype. Bacteria seem to express only one or two EGMs at any given time. Within one EGM, the enzyme levels still need to be tuned to maximise growth rate. I will introduce an adaptive control theory with which cells can change their enzyme levels to optimise growth rate, in changing environmentalconditions, but without having direct information about such changes.
I will finish by giving an example how the theory may elucidate curious experimental findings on single cell growth behaviour in E. coli.