Isolation and characterization of a novel bacteriophage infecting Vibrio alginolyticus
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Vibrio alginolyticus is a common marine bacterium implicated in disease outbreaks in marine farmed fish and invertebrates. Due to the inappropriate use of antibiotics in aquaculture, alternative therapies have been proposed. One of the most promising options is the use of lytic bacteriophages to control pathogenic bacteria. This work describes the isolation and characterization of a lytic phage (VEN) against a V. alginolyticus strain (V2) isolated from a disease outbreak in common dentex (Dentex dentex) cultured at the Hellenic Centre for Marine Research (HCMR) in Crete, Greece. The bacteriophage is morphologically similar to phages from Podoviridae family and remained stable for 1 year at 4 °C and over 1 h when kept at 50 °C. VEN was able to lyse the host bacteria at several multiplicity of infection (MOI) (0.1–100) in liquid cultures. However, it was unable to infect other V. alginolyticus strains. Its genome consists of 44,603 bp with a GC content of 43.5%, while sequence analysis revealed the presence of 54 potential ORFs with a T7-like genomic organization. Almost 65% of the predicted ORFs presented homology with proteins of the vibriophages Vc1 and phi-A318 infecting Vibrio cyclitrophicus and Vibrio alginolyticus, respectively. Phylogenetic analysis applying the amino acid sequence of the large terminase subunit confirmed the close relationship of these phages. Furthermore, the comparison of the RNA polymerase of these phages revealed that the motifs A, B and C related to the catalytic activity and the recognition loop related to promotor identification were also conserved. VEN has an obligate lytic life cycle demonstrated by experimental data and genomic analysis. These results suggest that VEN may provide a good candidate to control recurrent diseases caused by V. alginolyticus at HCMR.
KeywordsPhage Vibrio Genome analysis Aquaculture
The authors would like to thank Roche Hellas as well as Jon-Bent Kristoffersen and Vasiliki Terzoglou for sequencing support. This work was supported by FISHPHAGE project 131 and ANNOTATE project (674), funded by the European Social Fund and Greek National resources under the “Excellence” scheme, NSRF 2007–2013 and by AQUAPHAGE (project 269175), FP7, Marie Curie IRSES 2010.
RB and PK conceived the experiments, CK, MM, RB and ES conducted the experiments, CK, ES, PK and RB analyzed the results. All authors assisted in writing the manuscript, discussed the results and reviewed the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no competing financial interests.
No special permission was required for this study.
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