Immune Loss as a Driver of Coexistence During Host-Phage Coevolution [article]

Jake L Weissman, Rayshawn Holmes, Rodolphe Barrangou, Sylvain Moineau, William F Fagan, Bruce R Levin, Philip LF Johnson
2017 bioRxiv   pre-print
Bacteria and their viral pathogens face constant pressure for augmented immune and infective capabilities, respectively. Under this reciprocally imposed selective regime, we expect to see a runaway evolutionary arms race, ultimately leading to the extinction of one species. Despite this prediction, in many systems host and pathogen coexist with minimal coevolution even when well-mixed. Previous work explained this puzzling phenomenon by invoking fitness tradeoffs, which can diminish an arms
more » ... dynamic. Here we propose that the regular loss of immunity by the bacterial host can also produce host-phage coexistence. We pair a general model of immunity with an experimental and theoretical case study of the CRISPR-Cas immune system to contrast the behavior of tradeoff and loss mechanisms in well-mixed systems. We find that, while both mechanisms can produce stable coexistence, only immune loss does so robustly within realistic parameter ranges.
doi:10.1101/105908 fatcat:dyqrxurysnenripc6s3v2qz4wa