CLONING OF THE EARLY PROMOTERS OF PSEUDOMONAS-AERUGINOSA BACTERIOPHAGE-D3 - SEQUENCE OF THE IMMUNITY REGION OF D3

The early promoters of bacteriophage D3 of Pseudomonas aeruginosa were cloned and physically mapped to the right 25% of the phage genome. Th e promoters were cloned into promoter selection vector pQF26, and thei r relative strengths, the direction of transcription, and whether they were directly regulated by repressor were determined. A 3.3-kb fragme nt of the genome containing the immunity region was sequenced and anal yzed (GenBank accession number: L22692). The promoter activity associa ted with this region was determined to be bidirectional and repressibl e, indicating that this region contains operator-promoter complexes. S equence and functional analyses suggest that this region is analogous to the immunity region of coliphage lambda. Two strong promoters, one of which was repressible, were found to be located adjacent to the imm unity region. Clear-plaque mutant phage D3c contains insertion element IS222, which causes it to behave as a repressor-negative (cl) variant . The site of insertion of IS222 was sequenced and determined to lie w ithin the cl gene open reading frame. This phage shows remarkable simi larity in genomic organization to coliphage lambda and its relatives.