Memory in Bacteria: From Single Cells to Ecologies

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Synopsis

Bacteria have a very large toolbox of molecular mechanisms, coded by specific genes, which enable survival under stressful conditions. But these mechanisms on their own are often inefficient or costly, and only by using them strategically do bacteria gain a long-term advantage. This talk examines the strategies that bacteria use to regulate their survival toolbox.

By encoding and using memory in different ways, bacteria can optimize their long-term growth potential. This optimization can be understood by a statistical mechanics analogy. I describe a phase diagram structure in which memory levels are optimized as a function of the statistics of a randomly fluctuating environment, and a bacterial survival strategy can undergo different types of phase transitions.

I will illustrate these ideas using two groundbreaking experiments in microbiology, one which led to the discovery of gene regulation by Jacques Monod in the 1940's, and the second on co-evolution of bacteria and phages by Meyer, Lenski and co-workers in the 2010's. In both cases, bacteria encode memory of previous stresses and use it to their advantage.