A VIRULENT BACTERIOPHAGE OF LACTOCOCCUS-GARVIEAE (FORMERLY ENTEROCOCCUS-SERIOLICIDA) ISOLATED FROM YELLOWTAIL SERIOLA-QUINQUERADIATA

A virulent bacteriophage, designated PLgY, was detected from cultures of Lactococcus garvieae (formerly Enterococcus seriolicida) isolated f rom diseased yellowtail Seriola quinqueradiata. The phage had an isome tric head measuring 50 to 60 nm, a thin flexible tail of 7 x 140-180 n m, and the genome consisting of double stranded DNA, indicating that P LgY is a member of the family Siphoviridae. Of 26 strains of L. garvie ae examined, 24 were sensitive to the phage but 2 strains of L. garvie ae and another 22 strains of bacteria including fish and shellfish-pat hogenic bacteria were not. Lysis of L. garvieae cells due to the phage infection was dependent on culture temperature and occurred at betwee n 17 and 29 degrees C. Although an infection experiment of young yello wtail revealed that the 2 phage-insensitive L. garvieae strains were l ess virulent than 2 phage-sensitive strains, there was no correlation between phage sensitivity and antigenic variation.