A Virulent Phage Infecting Lactococcus garvieae, with Homology to Lactococcus lactis Phages
ABSTRACTA new virulent phage belonging to theSiphoviridaefamily and able to infectLactococcus garvieaestrains was isolated from compost soil. Phage GE1 has a prolate capsid (56 by 38 nm) and a long noncontractile tail (123 nm). It had a burst size of 139 and a latent period of 31 min. Its host range was limited to only twoL. garvieaestrains out of 73 tested. Phage GE1 has a double-stranded DNA genome of 24,847 bp containing 48 predicted open reading frames (ORFs). Putative functions could be assigned to only 14 ORFs, and significant matches in public databases were found for only 17 ORFs, indicating that GE1 is a novel phage and its genome contains several new viral genes and encodes several new viral proteins. Of these 17 ORFs, 16 were homologous to deduced proteins of virulent phages infecting the dairy bacteriumLactococcus lactis, including previously characterized prolate-headed phages. Comparative genome analysis confirmed the relatedness ofL. garvieaephage GE1 toL. lactisphages c2 (22,172 bp) and Q54 (26,537 bp), although its genome organization was closer to that of phage c2. Phage GE1 did not infect any of the 58L. lactisstrains tested. This study suggests that phages infecting different lactococcal species may have a common ancestor.