We used R2-pyocin-containing lysates from the standard laboratory strain PAO1, a PAO1 R-pyocin null mutant lacking a functional R-pyocin (PAO1ΔR), a previously described CF isolate, A018 (also a R2-pyocin producer), and a corresponding R-pyocin null mutant (25, 64, 65). Here, SMOX is linked to cystic fibrosis.