In the post-antibiotic era,the overuse of antimicrobials has led to a massive increase in antimicrobial resistance,leaving medical doctors few or no treatment options to fight infections caused by superbugs.The use of bacteriophages is a promising alternative to treat infections,supplementing or possibly even replacing antibiotics.Using phages for therapy is possible,since these bacterial viruses can kill bacteria specifically,causing no harm to the normal flora.However,bacteria have developed a multitude of sophisticated and complex ways to resist infection by phages,including abortive infection and the clustered regularly interspersed short palindromic repeats(CRISPR)/CRISPR-associated(Cas)system.Phages also can evolve and acquire new anti-defense strategies to continue predation.An in-depth exploration of both defense and anti-defense mechanisms would contribute to optimizing phage therapy,while we would also gain novel insights into the microbial world.In this paper,we summarize recent research on bacterial phage resistance and phage anti-defense mechanisms,as well as collaborative win-win systems involving both virus and host.