A Nature Biotechnology paper reported a new metagenomic‑editing platform that integrates large DNA sequences into gut bacteria directly in vivo. The method enables targeted insertion of multi‑kilobase constructs into resident microbes without ex vivo culturing, expanding capabilities for engineering the microbiome inside the host. Authors demonstrated the approach in preclinical models, showing stable genomic integration and expression of synthetic pathways in gut bacteria. The technique bypasses many limitations of current microbiome engineering—namely, delivery, colonization and genetic stability—by editing bacteria where they naturally reside. The advance opens doorways to in situ microbial therapeutics for metabolic disease, infection resistance and drug metabolism modulation, while also raising regulatory and biosafety questions about irreversible edits in complex ecosystems.