Bridging continuous and discrete evolution through a controllable, hypermutagenic phage-bacteria system

Lytic selection and evolution (LySE) is a T7-based method for near-continuous directed evolution of bacterial gene clusters that keeps discrete checkpoints: a hypermutagenic T7 DNA polymerase mutates a target gene cluster carried on a T7 phagemid, and alternating lysis and transduction cycles discard off-target genomic mutations. It evolved a 25-fold increase in tetA-encoded tigecycline resistance in 5 cycles and a 50.9% increase in endpoint biomass of a strain using ethylene glycol as its sole carbon source (Nature Microbiology, 2026).