Identification of the second attachment site for HP1 and S2 bacteriophages in Haemophilus influenzae genome

Presented data demonstrate that both HP1c1 and S2 bacteriophages of Haemophilus influenzae can use two related attB sites on the host chromosome. The first indication comes from the analysis of the whole genome sequence of H. influenzae Rd in which a second region of nucleotide sequence identical with the known attB site was detected. The location of both attB sites agrees with results of earlier field-inversion gel electrophoresis (FIGE) analysis of S2 and HP1c1 lysogens of H. influenzae. Functionality of cloned attB sites in the integration process of both phages was confirmed using in vivo integrase-dependent recombination system in Escherichia coli. Presented results seem to extend previously described similarities between S2 and HP1c1 phages.