On survival and gene expression during E. coli starvation - Thomas Julou (Biozentrum, Basel, Switzerland)

It is widely believed that bacteria spend most of their life in a non-growing state. However, despite major clinical and ecological implications, very little is known about what controls survival and what determines bacterial phenotypes when nutrients are depleted. In this talk, I will report on several aspects of bacterial starvation. First, we showed that, like the growth rate, the mortality rate during carbon starvation depends critically on subtle differences in environmental conditions. Second, we found that phenotypes are shaped early on upon entry into starvation and last during several days. For this, using a newly designed microfluidic device in combination with fluorescence time-lapse microscopy and automated image analysis, we measured gene expression during starvation by quantifying volumic production of proteins across time in single cells. By combining the observed time-dependent protein production and independently measured degradation rates, we show how protein concentrations deep into stationary phase are determined mainly by the expression dynamics in the first 10 hours of starvation. Finally, using perturbation experiments in which gene expression is inhibited for different periods, we also established that both survival and tolerance to stress during starvation depend strongly on this early expression program. Taken together, these results provide a first quantitative picture of cell maintenance, and provide a starting point for studying the emergence of specific phenotypes when nutrients become scarce.

Contact: Natale Scaramozzino