LAUSR

Significance Microbial consortia possess a wealth of genetic information; however, current approaches to deciphering genetics in a community context are largely constrained by low delivery efficiencies and a breadth of targeting specificities. Here, we describe a phage-based approach for precision editing of an individual gene within a target host organism in a community context. Engineering bacteriophage λ to contain a cytosine base editor, we inactivate host chromosomal and plasmid-based genetic targets through the strategic introduction of single-nucleotide mutations without Cas-based double-strand DNA cleavage. Next, we establish species- and site-specific editing within a synthetic soil community by using a fabricated ecosystem. Phage-assisted delivery, together with base editing, offers an important in situ editing approach for the genetic interrogation of microbial community members.