MOLECULAR CHARACTERIZATION OF LACTOCOCCAL BACTERIOPHAGE-TUC2009 AND IDENTIFICATION AND ANALYSIS OF GENES ENCODING LYSIN, A PUTATIVE HOLIN, AND 2 STRUCTURAL PROTEINS

Bacteriophage Tuc2009 is a temperate bacteriophage with a small isomet ric head and is isolated from Lactococcus lactis subsp. cremoris UC509 . The phage genome is packaged by a headful mechanism, giving rise to circularly permuted molecules with terminal redundancy. The unit genom e size is approximately 39 kb. A map of the phage genome on which seve ral determinants could be localized was constructed: pac, the site of initiation of DNA packaging; lys (1,287 bp), specifying the phage lysi n; S (267 bp), specifying a putative holin; and mp1 (522 bp) and mp2 ( 498 bp), each specifying one of the phage's structural proteins. lys, S, mp1, and mp2 were further characterized. lys and S are partially ov erlapping and appear to be part of one operon. The lysin shows homolog y to the lysins of the Streptococcus pneumoniae phages Cp-9, Cp-l, and Cp-7. The putative holin, which is thought to be involved in the rele ase of lysin from the cytoplasm, contains two strongly hydrophobic pre sumptive transmembrane domains and a highly charged C-terminal domain.