Virus classification - where do you draw the line?

Area of Science:

• Virology
• Bioinformatics
• Genomics

Background:

• High-throughput sequencing (HTS) has discovered numerous novel viruses, challenging traditional virus taxonomy based on phenotypic traits.
• Metagenomic data lacks phenotypic information, necessitating sequence-based classification methods.
• The International Committee on Taxonomy of Viruses (ICTV) lacks clear guidelines for classifying novel viruses based on genetic relatedness.

Purpose of the Study:

• To develop and apply a method for scoring genomic dissimilarity between viruses.
• To evaluate the consistency of current virus taxonomy with genomic relatedness.
• To provide a framework for classifying novel viruses from metagenomic data.

Main Methods:

• Developed the Genome Relationships Applied to Virus Taxonomy (GRAViTy) method to score genomic dissimilarity.
• Applied GRAViTy to assess taxonomic assignments of currently classified eukaryotic and prokaryotic viruses.
• Analyzed genomic relatedness at family and genus levels for various virus types.

Main Results:

• Found strong consistency between genomic relatedness and taxonomic assignments for eukaryotic viruses.
• Identified that prokaryotic virus family assignments are made at a different genetic level than eukaryotic families.
• Demonstrated that current prokaryotic virus subfamily groupings better match eukaryotic virus family levels.

Conclusions:

• Genomic relatedness largely underpins current virus family and genus assignments.
• The GRAViTy method offers an objective approach for classifying metagenomic viruses.
• Findings support ongoing revisions in bacteriophage taxonomy and provide a future direction for evidence-based virus classification.