Abstract
Viruses are the most abundant biological entities in the oceans, and account for a significant amount of the genetic diversity of marine ecosystems. However, there is little detailed information about the biodiversity of viruses in marine environments. Rapid advances in metagenomics have enabled the identification of previously unknown marine viruses. We performed metagenomic profiling of seawater samples collected at 6 sites in Goseong Bay (South Sea, Korea) during the spring, summer, autumn, and winter of 2014. The results indicated the presence of highly diverse virus communities. The DNA libraries from samples collected during four seasons were sequenced using Illumina HiSeq 2000. The number of viral reads was 136,850 during March, 70,651 during June, 66,165 during September, and 111,778 during December. Species identification indicated that Pelagibacter phage HTVC010P, Ostreococcus lucimarinus OIV5 and OIV1, and Roseobacter phage SIO1 were the most common species in all samples. For viruses with at least 10 reads, there were 204 species during March, 189 during June, 170 during September, and 173 during December. Analysis of virus families indicated that the Myoviridae was the most common during all four seasons, and viruses in the Polyomaviridae were only present during March. Viruses in the Iridoviridae were only present during three seasons. Additionally, viruses in the Iridoviridae, Herpesviridae, and Poxviridae, which may affect fish and marine animals, appeared during different seasons. These results suggest that seasonal changes in temperature contribute to the dynamic structure of the viral community in the study area. The information presented here will be useful for comparative analyses with other marine viral communities.
Highlights
Over the past two decades, studies of marine viruses with electron and fluorescence microscopy have revealed an unexpected abundance of virus particles, at 106 to109 particles per mL of seawater [1, 2]
The resulting taxonomic comparison of these samples shows the relative proportions of different marine viruses
Species-level analysis indicated that Pelagibacter phage HTVC010P (36%) was the most abundant species, followed by Ostreococcus lucimarinus virus OIV5 (8%) and Roseobacter phage SlO1 (6%) (Fig 3B)
Summary
Over the past two decades, studies of marine viruses with electron and fluorescence microscopy have revealed an unexpected abundance of virus particles, at 106 to109 particles per mL of seawater [1, 2]. Advances in generation sequencing and sequence assembly techniques provide metagenomics studies with access to large genomic fragments rather than short reads, a previous limitation. These large assembled sequences provide access to the genome content and structure of uncultured viruses, and thereby allow unique insights into the main viral families in the environment [9]. Viral metagenomics studies extract nucleic acids directly from viral particle-enriched environmental samples, analyze these samples by next-generation sequencing [10], and use bioinformatics to analyze the numerous sequences. One of the difficulties of marine viral metagenomics is the enrichment of viral particles from environmental samples. The flocculation, filtration, and re-suspension (FFR) method using FeCl3, which can enrich large volumes of marine viruses quickly and without expensive equipment, is frequently used to concentrate and extract marine viruses [11]
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