Putative archaeal viruses from the mesopelagic ocean

Area of Science:

• Marine microbiology
• Virology
• Bioinformatics

Background:

• Ocean viruses, particularly phages infecting bacteria, significantly impact marine ecosystems.
• Viruses infecting marine Archaea are crucial but remain understudied.
• Understanding archaeal virus ecology is vital for marine biogeochemical cycling.

Purpose of the Study:

• Introduce MArVD (Metagenomic Archaeal Virus Detector), a novel tool for identifying archaeal virus contigs in metagenomic data.
• To benchmark MArVD's accuracy and sensitivity in detecting known archaeal viruses.
• To explore the diversity and ecology of archaeal viruses in the Eastern Tropical North Pacific oxygen minimum zone.

Main Methods:

• Development and public release of the MArVD annotation tool via the iVirus platform.
• Benchmarking MArVD against a curated dataset of known viruses using VirSorter.
• Application of MArVD to viral metagenomes from the ETNP, followed by network-based classification and ecological analyses.

Main Results:

• MArVD demonstrated >99% accuracy and 100% sensitivity in identifying known archaeal viruses.
• 43 new putative archaeal virus genomes were discovered in the ETNP, ranging from 10 to 31 kb.
• These viruses, classified into six novel candidate genera, showed correlations with oxygen and temperature, with peak diversity in surface waters.

Conclusions:

• MArVD provides a reliable method for identifying archaeal viruses in sequence datasets.
• The study offers initial insights into the ecology of archaeal viruses in non-extreme marine environments.
• Archaeal virus diversity and abundance are linked to environmental conditions and host community structure, with *Thermoplasmata* suggested as hosts in surface waters.