Fig. 1
From: Anti-phage islands force their target phage to directly mediate island excision and spread
PLE circularizes during ICP1 infection and this response is dependent on PLE-encoded Int. a ICP1 injects its DNA into a PLE+ V. cholerae cell, leading to (1) PLE induction. (2) Induced PLE excises from the chromosome and circularizes, replicating to high copy number20. Through an unknown mechanism, (3) PLE inhibits the ICP1 replication program and protects the V. cholerae population from ICP1 predation. b Model of LSR/RDF mediated integration and excision of PLE and the resulting att sites. Black arrows indicate primers used to detect PLE circularization. c Circularized PLE, which is detected by PCR using outward-facing primers internal to the PLE, is found in cholera patient stool samples when PLE 1 and ICP1 are both present. d Detection of PLE 1 circularization during ICP1 infection. V. cholerae with the PLE 1 variant indicated was infected with ICP1 at a multiplicity of infection (MOI) of 5 and harvested 5 min post infection to detect PLE circularization. Strains complemented with a plasmid harboring int under control of an IPTG inducible Ptac promoter or the empty vector (EV) control were induced 20 min prior to phage infection. e Western blot for PLE 1 harboring endogenously FLAG-tagged Int shows Int expression independent of ICP1 infection. Samples of PLE 1 FLAG-Int or untagged PLE 1 Int were collected at the indicated timepoints after infection by ICP1. f PLE circularization is not necessary to block ICP1 plaque formation. Tenfold dilutions of ICP1 were spotted onto the listed V. cholerae lawns to observe the ability to form plaques (dark spots, zones of killing). ICP1 is unable to form plaques on PLE 1 even in the absence of int, while the CRISPR proficient phage is able to overcome PLE 1 and form plaques18. Uncropped gels are presented in Supplementary Fig. 5
