Relationships by DNA homology between lactococcal phages 7–9, P335 and New Zealand industrial lactococcal phages

Abstract

Phage 7–9 showed partial homology with phage P335, and it is proposed that phage 7–9 belongs to species P335. No relationships were detected between 7–9 and phages of the commonly found 936 species. Strong homology was found between phage 7–9 DNA and DNA from two lytic phages (1483 and 1741) isolated in 1980 and 1992 in New Zealand. The 1.6 kb DNA fragment from the phage 7–9 genome previously reported as highly conserved was not detected in any other phage studied. Phage P335 was related most closely to four temperate phages, to lytic industrial phages 1483 and 1741, and to phage 7–9. Most recently isolated industrial phages belonged to species 936, but some phages showed varying degrees of homology with phage P335. It is evident that phages grouped in species P335 show some variation in the degree of DNA homology with one another, and that this group warrants further study. Phage P335 is closely related to temperate phages and it is possible that recombination events have led to the incorporation of temperate or prophage DNA into the genomes of some lytic phages, leading to the development of ‘new’ industrial phages