Sequencing and analysis of the genome of lactococcal phage c2

Abstract The genome of lactococcal prolate-headed phage c2 was sequenced and found to be 22163 bp in length. Early and late genes were identified by transcription mapping. Six putative early promoters and a divergently orientated late promoter were identified. The transcription sites of the early promoters were mapped and the sizes of several transcripts were determined by Northern hybridization. The early region (approximately 6 kb) contained 22 open reading frames (ORFs), and the late region (approximately 16 kb) contained 17 ORFs. N-terminal amino acid sequences were determined for three major and eight minor phage structural proteins, and the gene sequences identified in the late region. Immunogold electron microscopy was used to distinguish major head and tail proteins, and the tail adsorption protein. The late region also contained the phage lysin gene which was cloned and expressed in Escherichia coli . A 521 bp sequence located between the early and late regions was shown to act as an origin of replication in Lactococcus lactis when cloned into the vector pVA891, indicating that the cloned sequence contains an ori . The cos region was elucidated, and the termini of the genome were shown to be complementary non-symmetrical 9 base single-stranded 3' extended DNAs. A putative terminase binding site was identified.