This study investigated the presence of prophagesin Lactococcus garvieae isolated from several marinefish species in Japan. Representative strains of 16bacterial genotypes (S1–S16) selected from morethan 400 L. garvieae isolates were used to inducelysogenic bacteriophages. These strains were treated with 500 ng mL 1 freshly prepared mitomycin C. A cross-spotting assay was performed tovalidate the lysogenic and indicator strains. Thelysogenic strains were selected for isolation andconcentration of the phages. Phage DNA wasdigested with EcoRI for biased sinusoidal field gelelectrophoresis analysis. Polymerase chain reaction(PCR) was used to detect integrated prophageDNA. Of the 16 representative bacterial genotypes, 12 strains integrated prophages as indicatedby the PCR assay, and 10 phages were detectedand isolated using two indicator bacterial strains.Analysis of genomic DNA showed that thesephages were homologous and named as PLgT-1.Transmission electron microscopy revealed thatthe morphology of PLgT-1 was consistent withthe virus family Siphoviridae. PCR analysis of theprophage DNA revealed that all of the S1 genotype strains were lysogenic (30/30), but none ofthe S16 genotype strains were lysogenic (0/30).This is the first study to investigate lysogenic bacteriophages from L. garvieae.Keywords: characterization, induction, Lactococcusgarvieae, lysogenic bacteriophage, marine fish
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