by Roberto — Phage-bac­te­ria pop­u­la­tion dy­nam­ics can be re­mark­ably com­plex. This is re­flected in the nat­ural his­tory of both; new phage de­fense sys­tems in bac­te­ria and anti-de­fense sys­tems in phage seem to be dis­cov­ered daily. Be­hind these in­tri­cate strate­gies to help in the re­pro­duc­tive suc­cess of each lies the ba­sic prob­lem of any preda­tor-prey re­la­tion­ship.