University of Otago researchers developed a CRISPR-based method for genome-wide mutagenesis of bacteriophages, enabling systematic disruption of phage genes while keeping essential functions intact. Published in Nature Microbiology, the workflow combines transposon insertion sequencing with CRISPR–anti-CRISPR selection to distinguish dispensable genes from those required for phage survival. Beyond mapping “phage dark matter,” the method can insert new genetic cargo—supporting engineering of phages to overcome bacterial defenses. The platform is positioned as both broadly applicable and cost-effective for accelerating phage discovery and therapeutic development. For antimicrobial resistance efforts, it provides a more scalable route to designing next-generation phage candidates rather than relying on slow, gene-by-gene engineering cycles.