Even microbes know not to change a winning team

What is it about?

How is it possible that microbial populations can robustly adapt to an immense variety of environments when their regulatory circuitry is extremely noisy and of limited accuracy? We propose that the remarkable adaptability of microbial populations can be explained by the combined effects of two experimentally observed phenomena: 1) that gene regulation is inherently noisy, causing individual cells to randomly switch between different phenotypic states, and 2) that the slower cells grow, the noisier they become. As a consequence, whenever cells encounter a new environment, they stochastically explore new phenotypes, only to stabilize after reaching a fast-growing phenotype. We propose that this growth rate dependent stability may play an important role in adaption of all microbes.

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Photo by CDC on Unsplash

Photo by CDC on Unsplash

Why is it important?

It has long been appreciated that random phenotype switching (bet-hedging) can aid microbial adaptation to uncertain futures. The random switching creates diversity in the population that ensures that there is always a subpopulation of individuals that is pre-adapted, whatever the future brings. Until now, this was only believed to work when the changes in the environment were slow or relatively predictable. However, these investigations did not account for the natural dependency of the phenotype switching rate on the growth rate, which causes cells to be more explorative when they grow slow and more stable when they grow fast. We account for this growth rate dependent stability and show that it enormously extends the type of changing environments in which bet-hedging populations can thrive.