Regime shifts in a phage-bacterial ecosystem and strategies for its control*

We show [1] that phage-bacterial ecosystems can have several alternative species compositions separated by abrupt regime shifts. In one of these states the fast-growing bacteria competitively exclude the slow-growing species by depleting common nutrient. In the other state the slow-growing bacteria with a large burst size make so many phages that the other species cannot survive. This scenario can be realized e.g. if two bacterial strains are protected from the same phage by, respectively, abortive infection or CRISPR, and partial resistance defence mechanisms. Alternative stable states and regime shifts greatly complicate the task of manipulation of microbial communities. We propose and study a successful control strategy via short population pulses aimed at inducing the desired regime shifts. In particular, we predict that a fast-growing pathogen could be eliminated by a combination of its phage and a slower-growing susceptible host.

[1] S Maslov, K Sneppen, mSystems (in press), https://doi.org/10.1101/797456