Molecular characterization of a new abortive infection system (AbiU) from Lactococcus lactis LL51-1

This study reports on the identification and characterization of a novel ab ortive infection system, AbiU, from Lactococcus lactis. AbiU confers resist ance to phages from the three main industrially relevant lactococcal phage species: c2, 936, and P335. The presence of AbiU reduced the efficiency of plaquing against specific phage from each species as follows: 3.7 x 10(-1), 1.0 x 10(-2), and 1.0 x 10(-1), respectively. abiU involves two open readi ng frames, abiU1 (1,772 bp) and abiU2 (1,019 bp). Evidence indicates that A biU1 is responsible for phage resistance and that AbiU2 may downregulate ph age resistance against 936 and P335 type phages but not c2 type phage. AbiU appeared to delay transcription of both phage 712 and c2, with the effect being more marked on phage c2.