<i>In situ</i> targeted mutagenesis of gut bacteria

Abstract Microbiome research is revealing a growing number of bacterial genes that impact our health. While CRISPR-derived tools have shown great success in editing disease-driving genes in human cells, we currently lack the tools to achieve comparable success for bacterial targets. Here we engineer a phage-derived particle to deliver a base editor and modify E. coli colonizing the mouse gut. This was achieved using a non-replicative DNA payload, preventing maintenance and dissemination of the payload, while allowing for an editing efficiency of up to 99.7% of the target bacterial population. The editing of a β-lactamase gene resulted in the stable maintenance of edited bacteria in the mouse gut at least 42 days after treatment. By enabling the in situ modification of bacteria directly in the gut, our approach offers a novel avenue to investigate the function of bacterial genes and provides an opportunity to develop novel microbiome-targeted therapies.