Bay of Bengal Virome: CUSAT-NIO's First Survey

Science and Environment - Internal (Mains: General Studies-III) | News context: 23 October 2026 (Times of India) | Dataset: 6 October 2026 (Zenodo) | Published: 24 October 2026

Why in the News

Sediment deposited on the ocean floor is one of Earth's largest microbial habitats, and scientists believe the largest unknown diversity of viruses lies hidden here. Indian researchers have now taken the first concrete step towards this unknown world. Researchers from Cochin University of Science and Technology (CUSAT) and the National Institute of Oceanography (NIO) have prepared the first 'virome' (the combined genetic picture of all viruses in an environment) of the Bay of Bengal's deep-sea sediment. A sample taken from a depth of 3,747 metres was genetically sequenced, and a key finding of the preliminary analysis is that about 70 per cent of viral sequences do not match existing reference databases - meaning they are likely signs of unknown viruses or viral lineages. The raw data of the sample was shared on the open repository Zenodo on 6 October 2026, and the news was published on 23 October 2026.

How the Work Was Done

Reading viruses directly from environmental samples is not easy - they have no universal conserved gene, their hosts often cannot be cultured in the laboratory at all, and the amount of nucleic acid is very small. The researchers therefore relied on metagenomics: viral particles were enriched from the sediment, nucleic acid was extracted, next-generation sequencing was carried out (Illumina NextSeq 2000, 2x150 base-pair reads), and bioinformatics tools were then used to match the sequences against known virus databases. The same team has also presented a comparison of the viromes of surface and deep sediments at the 2026 Ocean Sciences Meeting. The dataset deposited on Zenodo is raw viral metagenome data (CC-BY licence), which any laboratory in the world can re-analyse.

Why Viruses Matter in the Ocean

Viruses are the largest biological entity in the oceans and a leading cause of microbial death. In a process called the 'viral shunt', viruses burst their host cells and release their carbon and nutrients in dissolved form - this directly affects the nutrient cycle and the carbon pump. Many viruses also carry 'auxiliary metabolic genes' (AMGs), which rewrite the host's metabolic processes during infection. Without knowing deep-sea viruses, therefore, the full arithmetic of the marine carbon cycle remains incomplete. Viral diversity in sediment is far greater than in the water column - benthic ecosystems are counted among Earth's largest viral reservoirs.

What Was Known Earlier

This same team (Athira T. Menon and Swapna P. Antony, CUSAT) has earlier published the virome of coastal sediments off the Kerala coast (Journal of Earth System Science, 2025): about 40 viral families were found, in which the newly described Schitoviridae family and vibriophages were prominent; a complete vibriophage genome was also sequenced. In 2022, NIOT published the metagenome of microbes (bacteria) from the Bay of Bengal's deep sediment - dominance of Proteobacteria and genes linked to bioremediation were found. A 2023 study of water-column viruses has shown prokaryotic viruses and giant viruses (Megaviricetes). Globally, thousands of new viral populations were found in the sediments of the south-western Indian Ocean, and a 2023 global analysis counted more than 3.47 lakh deep-sea DNA viruses - most of them unclassified. In other words, the map of virus science in the Bay of Bengal was almost empty, and this work is the beginning of filling that gap.

Significance for India

Three points are noteworthy. First, alignment with the goals of the Deep Ocean Mission: this central sector programme of the Ministry of Earth Sciences was approved in 2021 at a cost of Rs 4,077 crore for five years (2021-26), under which the 'Samudrayaan' project aims to send three people to a depth of 6,000 metres (Matsya 6000). Such baseline mapping is consistent with the mission's 'deep-sea biodiversity' component - although this study's formal link with the mission is not publicly confirmed. Second, bioprospecting: unknown viruses and their enzymes can be reservoirs for industrial, pharmaceutical, and biotechnological applications - examples such as vibriophages in phage therapy also emerged in this team's coastal study. Third, climate science: the Bay of Bengal is the world's largest bay; without understanding its carbon cycle, regional climate models will remain incomplete.

Limitations and Cautions

Several things must be said honestly. First, this work has not yet been published as a peer-reviewed paper - the available material is the raw dataset, a conference abstract (2026 Ocean Sciences Meeting), and news reports; final findings may change when the published paper appears. Second, '70 per cent of sequences unclassified' does not mean 70 per cent new viruses have been found - it also reflects the limitations of reference databases; metagenomics can only match against known sequences, so the share of unknown viruses always appears higher. Third, the shared dataset is from a single location-depth (3,747 metres) - it cannot be generalised to the entire bay. Fourth, size-based filtration methods can leave out giant viruses, and read length and sequencing depth affect diversity estimates - these method-induced biases apply to every virome study. Fifth, the figures quoted in news reports are from preliminary analysis; exact numbers and methodological details will be available in the published paper.

Viromics: The Rise of a New Methodological Field

Over the past two decades, metagenomics has transformed virus science. Earlier, only those viruses could be identified whose hosts could be cultured in a laboratory; now, by reading sequences directly from environmental samples, millions of viral communities can be detected. But this method has its own costs: the process of separating viral particles from bacteria, the size of the filter, and the completeness of reference databases - all three change the results. This is why the international community is working on standards such as the 'uncertain viral operational taxonomic unit' (vOTU), so that different studies can be compared. This field has begun only recently in India - from a pilot project on the Arctic virome to the Kerala coast and now the depths of the Bay of Bengal. Every new dataset also enriches the global reference database, reducing the 'unclassified' share of the next study.

Way Forward

The next steps are clear: publication of a peer-reviewed paper, sampling from more depths and locations, isolation of viruses and direct evidence of host relationships, and AMG-based carbon-cycle modelling. A data-sharing framework under the Deep Ocean Mission (such as the C-DAC-NIOT marine biodiversity data project) can turn these datasets into a national resource. Comparing the viromes of coastal and deep sediments will also show whether river-borne terrestrial influence reaches the deep sea.

Sequence of Dates

Kerala-coast coastal virome study in 2025 (JESS); raw dataset on Zenodo on 6 October 2026; news coverage on 23 October 2026; conference presentation at the 2026 Ocean Sciences Meeting. Note: the dataset date and the news date are different, and the paper's publication date has not yet arrived.

Reference Points for the Reader

Remember three things. First, viruses are not only disease - in the ocean they regulate nutrient cycles and microbial balance; 'viral shunt' and 'AMG' are two exam-worthy terms. Second, 'not matching the database' is a sign of possible new diversity, not certain proof - classification depends on the limits of the reference. Third, open sharing of raw data (Zenodo, CC-BY) is itself a procedural achievement - it is a step towards transparent science and the democratisation of data under the Deep Ocean Mission.

Mains Practice Question

Why is the study of deep-sea viromes essential for understanding marine ecology and the carbon cycle? Evaluate the scientific, economic, and strategic significance of such research in the context of India's Deep Ocean Mission. (250 words, 15 marks)

The Unseen World of Viruses in the Bay of Bengal's Depths: CUSAT-NIO's First 'Virome' Survey