Viral Diversity in Hadal Biospheres

 By Karla Hinojosa

A. Diagram figure shows the locations of samples and types of samples used in the research article. B. Venn diagram figure shows the overall number of vOUTs that compose the OTVGD. C. Specific vOTUs and protein cluster percentages in seawater and sediment with the three public databases. D. Bar chart figure represents the taxonomic compositions of viruses grouped in types of samples and ocean trenches. The bars on the right side indicate the number of viral taxa in viruses. E. Bar graph figure shows the bacterial and archaeal hosts of viruses in ocean trenches. The bars located on the top and the bottom represent the ocean zone. The heatmap on the right lower side indicated the vOTUs with hosts. Figure taken from Jian et al. 2021. 

Viruses have a considerable influence and portray a big role in seawater and sediment-water. The diversity of viruses has been examined in surface water, but little to no research has been done in the hadal biosphere, the deepest section of the ocean with depths that exceed 6000 meters. The distribution, genetic characteristics, way of life, and ecological function of viruses found in seawater and sediment that inhabit the hadal biosphere were analyzed. Nineteen metagenomic samples were obtained from three Pacific Ocean trenches: Mariana, Yap, and Kermadec. From hadal ocean water and sediment samples, 108 archaeal and bacterial genomes, which included microbial isolate genomes, metagenomic bins, and single-cell genomes were collected. The Mariana Trench samples ranged from 0 to 10,500 meters deep, the Yap Trench samples were obtained from a depth of 6000 meters or deeper. To display sample locations and types, an oceanic trench viral genome dataset (OTVGD) was used. Additionally, viral contigs were categorized into virus operational taxonomic units or vOTUs. The vOTUs composed the OTGD. Three public databases, RefSeq Virus database, Global Ocean Viromes 2.0 (GOV), and IMG/VR were used in this study to investigate the novelty of OTVGD, vOTUs, and protein clustering. The link between various viruses and their hosts suggests that viruses manage microbial communities in seawater hadal biospheres. The results conclude a high number of viruses enriched in oceanic trenches have not been discovered yet. Thaumarchaeota, an archaeal phylum found in hadal environments, and Oleibacer, an abundant bacterial genus, are infected by hadal viruses. Hadal viruses were identified to adopt a lysogenic lifestyle as a result of hadopelagic water. AMGs (auxiliary metabolic genes) found in hadal virus genomes have been shown to play a role in host metabolism and biogeochemical cycles. Microbial metabolism, fatality, and nutrient recycling are all aided by viral populations in oceanic trenches, which have an impact on hadal ecosystems and overall marine life. There is further research to be done to gain a better understanding of hadal viruses. 

Jian, H., Yi, Y., Wang, J. et al. (2021). Diversity and distribution of viruses inhabiting the deepest ocean on Earth. ISME J 15, 3094-3110. https://doi.org/10.1038/s41396-021-00994-y