13h00 - 13h30 – Francis Mairet (Ifremer / Nantes)

Optimal proteome allocation determines temperature dependence of microbial growth laws

Although the effect of temperature on microbial growth has been widely studied, the role of proteome allocation in bringing about temperature-induced changes remains elusive. In this talk, I will present a coarse-grained model of microbial growth - including the processes of temperature-sensitive protein unfolding and chaperone-assisted (re)folding - that we develop to tackle this problem. We determine the proteome sector allocation that maximizes balanced growth rate as a function of nutrient limitation and temperature. Calibrated with quantitative proteomic data for Escherichia coli, the model allows us to clarify general principles of temperature-dependent proteome allocation and formulate growth laws. The same activation energy for metabolic enzymes and ribosomes leads to an Arrhenius increase in growth rate at constant proteome composition over a large range of temperatures, whereas at extreme temperatures resources are diverted away from growth to chaperone-mediated stress responses. Our approach points at risks and possible remedies for the use of ribosome content to characterize complex ecosystems with temperature variation.

13h30 - 14h00 – Antrea Pavlou (IBIS / Grenoble)

Insights into bacterial resource allocation in dynamically changing environments using a combination of experimental and mathematical approaches

with E. Cinquemani, H. Geiselmann, H. de Jong

The relationship between bacterial growth and the environment has been well characterized over the last 50 years. In most studies, however, bacteria are maintained at steady-state growth even though in reality they are rarely in a constant environment. To investigate bacterial adaptation in changing environments, we track growth and gene expression of single- cell bacteria growing in a microfluidic device in changing environments. We examine the behavior of specific ribosomal and metabolic genes in this context using fluorescent protein tags. The experimental results provide a detailed view of resource allocation strategies of bacteria in dynamically changing environments and are helpful in testing the predictions made by resource allocation models of bacterial growth.

Dernière modification le 02/04/2021