DNA HOMOLOGY IN SPECIES OF BACTERIOPHAGES ACTIVE ON PSEUDOMONAS-AERUGINOSA

Using electron microscopy and DNA-DNA-hybridization, 113 virulent and temperate bacteriophages specific for P. aeruginosa have been assigned to 23 species. In most cases, especially in virulent phages, both par ticle morphology and DNA homology types were in good correlation and t heir use was sufficient for clear-cut definition of phage species. No virulent phages of different species had any DNA homology. DNA homolog y was detected between temperate phages of several species. Temperate phages formed two large groups of two and seven species, respectively. The first group included all transposable bacteriophages. The extent of interspecies DNA homology of phages belonging to each group was not more than 10-15% (except for 25% for phages D 3 and KF 1). No DNA hom ology was between phages of different groups. The possible origin and function of homologous sequences (genetic modules, linkers, occasional insertional sequences) are discussed. One of the phages (phiC 15) may be considered as the result of recombination between phages belonging to two different species, 295 and SM.