The Lactococcal Abortive Phage Infection System AbiP Prevents both Phage DNA Replication and Temporal Transcription Switch

Abstract

ABSTRACT We describe here a new lactococcal abortive phage infection system, designated AbiP. AbiP is effective against some lactococcal phages of one prevalent group, 936, but not against phages from the other two groups (c6A and P335). It was identified in the Lactococcus lactis subsp. cremoris strain IL420, on the native plasmid pIL2614. AbiP is encoded by a single gene, expressed in an operon with a second gene. In this work, abiP is shown to affect both the replication and transcription of phage DNA. In AbiP + cells, phage DNA replication is arrested approximately 10 min after infection. Levels of middle and late phage transcripts are lower in AbiP + than in AbiP − cells, probably due to the smaller amount of phage DNA. By contrast, early phage transcripts are more abundant in AbiP + than in AbiP − cells, suggesting that the switch-off, which occurs 15 min after infection in AbiP − cells, is prevented in AbiP + cells.