“Marine archaea of the order Poseidoniales are abundant in surface oceans and contribute to organic-matter processing, yet the viruses associated with them remain poorly characterized. Aoguangviridae had been represented by only a small number of genomes, leaving its true diversity, evolutionary structure, functional potential, and global distribution largely unresolved. We therefore integrated public marine metagenomic and metatranscriptomic datasets to build a broader genomic framework for this archaeal virus family and to examine where its members occur and are active,” said Changyue Zhao, a researcher at the Ocean University of China in Qingdao, China.
Researchers used reference genomes to develop the reference dataset for Aoguangviridae. They incorporated five high-confidence genomes as seed genomes. These genomes were the first identified and well-characterized. They also added 54 additional Aoguangviridae-related genomes that had been developed during previous metagenomic studies. Metagenomics is the study of genetic material recovered directly from environmental samples. Any redundancies were removed.
Using comparative genomic analyses, the researchers identified eight single-copy core genes that provided a basis for examining evolutionary relationships within Aoguangviridae. Their expanded dataset increased the number of non-redundant genomes from 59 to 227 and revealed substantially greater diversity than previously recognized, encompassing 22 subfamilies, 157 genera, and 167 species.
“Aoguangviridae is far more diverse and widespread than previously recognized. We expanded the non-redundant genome set from 59 to 227 and resolved extensive diversity at the subfamily, genus, and species levels. These viruses occur across the global ocean, are particularly abundant in epipelagic and Arctic waters, and show transcriptional activity in the deep chlorophyll maximum. Their genomes also encode auxiliary metabolic genes, suggesting the capacity to influence host metabolism during infection,” said Zhao.
Aoguangviridae is found in marine and coastal habitats worldwide, but researchers found that there is variation within environments among lineages within the family. Some lineages were enriched in epipelagic and polar waters, whereas others were more frequently detected at greater depths. These contrasting distribution patterns suggest ecological differentiation within the family, with different lineages occupying distinct niches across the global ocean. Such ecological specialization may also be associated with differences in their interactions with Poseidoniales hosts and their roles in marine biogeochemical processes.
Looking ahead, researchers hope to find biological evidence for their genome-based predictions. “We aim to recover additional complete genomes, improve host assignments, and combine time-series meta-omics with laboratory cultivation and infection experiments. Ultimately, we want to determine how Aoguangviridae interacts with Poseidoniales cells and whether these infections measurably alter organic-carbon processing and other biogeochemical functions in the ocean,” said Zhao.
Other contributors include Kaiyang Zhang, Haolin Jia, Hongbing Shao, Andrew McMinn, Min Wang, and Yantao Liang of the Ocean University of China and Yeong Yik Sung, Wen Jye Mok, and Li Lian Wong of the UMT-OUC Joint Center for Marine Studies.
The Laoshan Laboratory, the Natural Science Foundation of China, the 2024 Graduate Self-Directed Research Project, and the Fundamental Research Funds for the Central Universities supported this research.
