Deep-Sea Deep Sequencing: A Showcase of Extraordinary Viral Diversity

 By: Umberto Fasci

 

Phylogenetic analysis of viral contigs from marine sediments, marine water, freshwater and terrestrial soil - proteome-wide similarity relationships. Figure taken from Zheng et al. 2021.

 

 This study with the fascinating aim to improve the knowledge of the virosphere in deep-sea sediments, investigates the viral diversity at both gene and genomic levels in the deep-sea sediments of the Southwest Indian Ocean. This alone seems ambitious. However, with the decreasing cost and increasing data acquisition of sequencing technologies, deep sequencing has become valuable for this use case. From their deep sequencing analysis, the researchers here found a large number of unclassified viral groups with a total of 1106 viral contigs. Amazingly, 217 of these expressed complete viral genomes with none clustered with any known viral genome. It was also found that over two thirds of the ORFs within these viral contigs encode for no known functions. This by itself is extraordinary, suggesting the the deep-sea sediments represent an enormous site for novel viral genotypes. Ultimately, this study opens a box which requires the right tools to access. With this, future related studies should explore how the novel viral metabolic genes found here may be involved in energy production, or amino acid synthesis pathways at this level of the marine environment. Elucidating this may improve our understanding of how involved these novel viral genes are in the marine sediment environment.

 

 

Zheng, X., Liu, W., Dai, X., Zhu, Yaxin, Wang, J., Zhu, Y., et al. (2021) Extraordinary diversity of viruses in deep-sea sediments as revealed by metagenomics without prior virion separation. Environ Microbiol 23: 728–743.