Known phyla dominate the Tara Oceans RNA virome

Area of Science:

• Virology
• Bioinformatics
• Marine Biology

Background:

• A recent study proposed five novel RNA virus phyla, suggesting dominance in oceanic environments.
• Two proposed phyla, 'Taraviricota' and 'Arctiviricota', were highlighted as particularly abundant.

Purpose of the Study:

• To re-evaluate the classifications and abundance of proposed new RNA virus phyla.
• To verify the claim of dominance of novel RNA virus phyla in marine ecosystems.

Main Methods:

• Re-mapping of sequencing reads to identify viral contigs and their taxonomic assignments.
• Independent virus identification and classification using bioinformatics tools.
• Phylogenetic analysis to determine the placement of novel sequences within established viral orders.
• Sequence alignment to identify potential non-viral origins of RNA-dependent RNA polymerase (RdRp)-like sequences.

Main Results:

• The vast majority (99.95%) of viral reads were assigned to known viral phyla, contradicting claims of new phylum dominance.
• Contigs assigned to proposed phyla represented a minimal fraction (2.8%) of total RdRp-containing contigs and an even smaller fraction (0.01%) of Arctic Ocean reads.
• Sequences from the proposed 'Pomiviricota' phylum were phylogenetically placed within the established order 'Durnavirales'.
• Specific sequences from the proposed 'Taraviricota' phylum showed high similarity to dinoflagellate proteins, suggesting a non-viral origin.

Conclusions:

• The data comprehensively refute the claim that the proposed new RNA virus phyla dominate marine viral communities.
• The majority of viral sequences belong to established viral lineages, with specific novel sequences potentially originating from host organisms.