Researchers at the University of Otago developed a CRISPR-based approach for genome-wide mutagenesis of bacteriophages, combining transposon insertion sequencing with CRISPR–anti-CRISPR selection. The method aims to identify essential genes across diverse phages and accelerate engineering of phage candidates. The workflow includes disrupting genes and inserting additional cargo sequences—such as fluorescent markers—enabling faster functional discovery and potential upgrades to help engineered phages overcome bacterial defense systems. The advance targets one of the biggest constraints in phage therapeutics: the large fraction of “microbial dark matter” phage genes without clear function that slows reliable development.