GENETIC AND SEQUENCE-ANALYSIS OF THE COS REGION OF THE TEMPERATE PSEUDOMONAS-AERUGINOSA-BACTERIOPHAGE, D3

The location and structure of the cos ends of bacteriophage D3, which infects Pseudomonas aeruginosa strain PAO, has been determined using a combination of deletion analysis, transposon mutagenesis, and sequenc ing directly off the phage DNA. Phage D3 was found to have 9-bp 3' cos ends, making it the first phage of a Gram-negative organism known to have 3' cos ends. A 700-bp region flanking the cos site was necessary for efficient transduction of D3 cosmid derivatives. This region was f ound to contain incomplete inverted repeat sequences flanking the cos site, along with adenine-rich repeats homologous to coliphage lambda T er binding sites. Possible IHF binding sites were also present.