FVE-novel: Recovering Draft Genomes of Novel Viruses and Phages in Metagenomic Data

Background Despite the recent surge of viral metagenomic studies, recovering complete virus/phage genomes from metagenomic data is still extremely difficult and most viral contigs generated from de novo assembly programs are highly fragmented, posing serious challenges to downstream analysis and inference. Results Here we develop FVE-novel, a computational pipeline for reconstructing complete or near-complete viral draft genomes from metagenomic data. FVE-novel deploys FastViromeExplorer to efficiently map metagenomic reads to viral reference genomes or contigs, performs de novo assembly of the mapped reads to generate scaffolds, and extends the scaffolds via iterative assembly to produce final viral scaffolds. We applied FVE-novel to an ocean metagenomic sample and obtained 268 viral scaffolds that potentially come from novel viruses. Through manual examination and validation of the ten longest scaffolds, we successfully recovered four complete viral genomes, two are novel as they cannot be found in the existing databases and the other two are related to known phages. Conclusions The hybrid reference-based and de novo assembly approach used by FVE-novel represents a powerful new approach for exploring viral diversity in metagenomic data. FVE-novel is freely available at https://github.com/saima-tithi/FVE-novel .