Induction and characterization of a lysogenic bacteriophage of Lactococcus garvieae isolated from marine fish species.

This study investigated the presence of prophages in Lactococcus garvieae isolated from several marine fish species in Japan. Representative strains of 16 bacterial genotypes (S1-S16) selected from more than 400 L. garvieae isolates were used to induce lysogenic bacteriophages. These strains were treated with 500 ng mL(-1) freshly prepared mitomycin C. A cross-spotting assay was performed to validate the lysogenic and indicator strains. The lysogenic strains were selected for isolation and concentration of the phages. Phage DNA was digested with EcoRI for biased sinusoidal field gel electrophoresis analysis. Polymerase chain reaction (PCR) was used to detect integrated prophage DNA. Of the 16 representative bacterial genotypes, 12 strains integrated prophages as indicated by the PCR assay, and 10 phages were detected and isolated using two indicator bacterial strains. Analysis of genomic DNA showed that these phages were homologous and named as PLgT-1. Transmission electron microscopy revealed that the morphology of PLgT-1 was consistent with the virus family Siphoviridae. PCR analysis of the prophage DNA revealed that all of the S1 genotype strains were lysogenic (30/30), but none of the S16 genotype strains were lysogenic (0/30). This is the first study to investigate lysogenic bacteriophages from L. garvieae.

Hoai TD ，Yoshida T 《-》

Properties and genomic analysis of Lactococcus garvieae lysogenic bacteriophage PLgT-1, a new member of Siphoviridae, with homology to Lactococcus lactis phages.

Hoai TD ，Nishiki I ，Yoshida T 《-》

Characterization of prophages of Lactococcus garvieae.

Eraclio G ，Fortina MG ，Labrie SJ ，Tremblay DM ，Moineau S ... -  《Scientific Reports》

Host range and influence of a cell capsule on the phage efficacy of three Lactococcus garvieae lytic phages.

Hoai TD ，Nishiki I ，Yoshida T ，Nakai T ... -  《DISEASES OF AQUATIC ORGANISMS》

Induction and characterization of lysogenic bacteriophages from Streptococcus iniae.

To investigate the presence of prophage in Streptococcus iniae, a highly problematic fish pathogen. Cross-spotting assays and mitomycin C inductions were conducted to screen for prophage in 48 Strep. iniae isolates. Bacteriophages were characterized by plaque assays, transmission electron microscopy and DNA restriction enzyme digestion. Plaque assays confirmed prophages in 14·6% of isolates. Phages vB_SinS-44, vB_SinS-45, vB_SinS-46 and vB_SinS-48 lysed 78·5% of Strep. iniae isolates and displayed distinctive host ranges. Microscopy revealed virions exhibiting long, non-contractile tails and isometric heads consistent with phages from the family Siphoviridae. Restriction digests revealed genome sizes ranging from 27·5 to 66·3 kbp, with distinct cutting patterns that indicate the presence of related prophages in bacteria isolated from different geographic regions. The rate of prophage carriage found is comparably low and induction rates varied between phages. The four characterized Siphoviridae phages have broad host ranges within the Strep. iniae isolates. This is the first description and characterization of lysogenic phages from Strep. iniae. These phages are candidates for research and diagnosis of the bacterium and their identification should accelerate the discovery of lytic phages to be trialled against Strep. iniae infections in fish.

Wright EE ，Elliman JR ，Owens L 《-》