SEQUENCING AND ANALYSIS OF THE COS REGION OF THE LACTOCOCCAL BACTERIOPHAGE-C2

The cohesive termini of the DNA genome of the lactococcal bacteriophag e c2 were directly sequenced and appeared to be complementary, non-sym metrical, 9-nucleotide single-stranded, 3' extended DNAs, with the fol lowing sequence: 5'-GTTAGGCTT-3' 3'-CAATCCGAA-5'. DNA located on eithe r side of the cohesive ends was sequenced and several repeats and a re gion with the potential for a DNA bend were found. Previously sequence d cos regions of 13 other bacteriophages were also examined for simila r sequence features. All of the bacteriophages from gram-positive host s had 3' extended DNA termini, in contrast to the bacteriophages from gram-negative hosts, which had 5' extended DNA termini. All bacterioph ages had a region of dyad symmetry close to the cohesive termini. A 7. 3 kb DNA fragment of the c2 genome containing the cos sequences was cl oned; transduction experiments demonstrated that these cloned sequence s could act as a substrate for packaging enzymes of phage c2.