title: Restriction modification systems as engines of diversity.
abstract: Restriction modification (RM) systems provide protection against a broad spectrum of phages. However, the likelihood of a phage permanently bypassing this can be as high as 0.1 per infection (Korona et al., 1993) which makes for a relatively weak defense. Here we argue that, apart from providing such transient defenses, RM systems can facilitate long-term coexistence of many bacterial strains. We show that this diversity can be as large as the burst size of the phage but no larger-a curious correspondence between a number at the level of species and another number at the level of individuals. Such a highly diverse and stably coexisting ecosystem is robust to substantial variation in both bacterial growth rates and strength of their RM systems, which might be one reason why quite weak RM systems exist in the wild.
authors.affiliation: Center for Models of Life, Niels Bohr Institute Copenhagen, Denmark.
authors.forename: Kim
authors.initials: K
authors.lastname: Sneppen
authors.affiliation: Center for Models of Life, Niels Bohr Institute Copenhagen, Denmark.
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Semsey
authors.affiliation: National Centre for Biological Sciences Bangalore, India.
authors.forename: Aswin S N
authors.initials: AS
authors.lastname: Seshasayee
authors.affiliation: Center for Models of Life, Niels Bohr Institute Copenhagen, Denmark ; National Centre for Biological Sciences Bangalore, India ; Simons Centre for the Study of Living Machines, National Centre for Biological Sciences Bangalore, India.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Krishna
keywords: bacteriophage defense; ecosystem diversity; epigenetic labeling; mathematical modeling; phage-bacteria interaction; population dynamics