THE RELATIONSHIP BETWEEN HP1 AND S2 BACTERIOPHAGES OF HAEMOPHILUS-INFLUENZAE

Comparison of the nucleotide sequences of the left arms of two Haemoph ilus influenzae phages, S2 and HP1 is presented. They exhibit a charac teristic mosaic pattern of homologous and non-homologous regions. The homology extends over the attP site and int, orf 5 to 9, rep and the 3 ' part of cI genes. Two major non-homologous regions were detected. On e is found between the int and cI genes; the other spans the region of promoters and the cox gene. Variations in the region of the promoters which is involved in the choice between a lysogenic and a lytic pathw ay and some divergences in the cI coding sequences are probably respon sible for the observed immunity differences between the two phages. Di stinctions in the distribution of consensus sequences for an integrati on host factor (IHF) and integrase-binding sites and promoters are des cribed. These data offer an explanation of the relationship between th ree types of S2/HP1 phages. It allows in turn a final settlement of th e nomenclature variation in the literature. The results presented, whi ch are similar to those obtained for other phage groups, suggest that the mosaic structure of phage genomes is a normal outcome of phage div ergence. (C) 1997 Elsevier Science B.V.