Proc Natl Acad Sci U S A. 2001 Apr 10;98(8):4552-7 doi:10.1073/pnas.071052198

Ghadessy FJ, Ong JL, Holliger P.

Directed evolution of polymerase function by compartmentalized self-replication.

No beads. A bacterial cel is used as a subcompartment maintaining gene and proteins together. Evidence for leakage of small molecules at high compartment density.