PA-005:

Metagenomic analysis of viral communities in Osaka bay, Japan

[Introduction] Marine viruses have important roles in microbial mortality and metabolic reprogramming as well as biogeochemical cycling. Here we succeeded in construction of 46 complete genomes from 9 viromes in Osaka bay (OBV) and characterized the abundant one.
[Materials and Methods] The viral particles was concentrated with iron chloride flocculation, then purified using density gradients centrifugation and enzymatic digestion. The viral dsDNA extracted was sequenced using MiSeq and Nextera XT library preparation. Genomic comparisons with OBV and known viruses were performed using TBLASTX searches. The genome frequency (FPKM) was calculated with Bowtie2. The correlation of the temporal patterns in genome frequency was analyzed in MeV.
[Results and Discussion] Except for two OBV genomes which showed entire co-linearity with Cyanophages P-RSM6 and Puniceispirillum phage HMO-2011, OBV genomes were distantly related to known viral genomes. Of 46 genomes, OBV24 showed the highest genome frequency, and the sequences assigned to the genome accounted for 0.6% of the whole virome sequences. OBV24 were similar to OBV23 and OBV25. These genomes showed partial co-linearity to 7 structural proteins of Cellulophaga (Bacteroidetes) podovirus phi38:1 which belongs to putative genus Cba401likevirus. Ribonucleotide reductases of the genomes formed a cluster consisting of only marine virome sequences. Auxiliary metabolic genes were not found on the genomes. However one gene of OBV25 was highly similar to marine Flavobacteriaceae family bacteria. The temporal patterns of the genome frequencies differed, and correlated with exchange of water masses, respectively. These suggest that the phages are widely distributed in the ocean and interact with oceanic and coastal Flavobacteriaceae bacteria. This work is supported by The Canon Foundation.

keywords:marine virus,virome,genome frequency,complete genome