A research team led by Prof. SUN Chaomin from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) has unveiled the crucial role of viruses in deep-sea carbon cycling and microbial community structure. Their findings were recently published in Nature Communications.

Viruses are the most abundant biological entities in the ocean, with an estimated 10³⁰ individuals globally and a biomass second only to that of prokaryotes. Beyond their classic role in host lysis, viruses influence microbial communities and biogeochemical cycles through horizontal gene transfer and metabolic reprogramming via auxiliary metabolic genes (AMGs). However, their ecological functions across extreme deep-sea habitats—such as hydrothermal vents, cold seeps, and trenches—remain one of the final frontiers in oceanography.

"Our current understanding of these viral functions is fragmented at best," said Dr. WANG Chong, the first author of the study. "Mapping viral diversity hotspots and decoding their functional signatures is not just a matter of academic curiosity; it is a scientific imperative to solve key puzzles in marine carbon cycling."

The researchers explored viral communities across four deep-sea sites: a fading cold seep, a site farther from cold seep activity, a newly forming cold seep, and a seamount. Using advanced genetic sequencing techniques, they uncovered extensive viral diversity in sediments, including numerous previously unknown DNA and RNA viruses.

Notably, RNA viruses exhibited unique host preferences and lifestyles compared to DNA viruses. Critically, the team found that active viral genes enhanced the hosts' ability to digest recalcitrant organic matter, providing direct evidence that viruses drive carbon processing in deep-sea ecosystems.

Dr. WANG noted, "This study represents our first in-depth exploration of the viral frontier in the deep sea. While we have long recognized the exceptional capacity of deep-sea microbes to break down complex organic matter, this study connects the dots, revealing how viruses actively collaborate with their hosts to facilitate this vital process."

By investigating sediments from diverse cold seep and seamount environments, the study highlights thepotential of viruses to assist host organisms in metabolizing complex organic matter. These findings offer new perspectives on energy flow and material cycling in extreme deep-sea habitats.

Representative images of virus-like particles. (Image by IOCAS)