Chinese scientists have made an unexpected discovery in tidal flats. These areas harbor far more giant viruses than previously thought, including a previously unknown family. The study refutes earlier assumptions that viruses in coastal sediments are similar to those in the ocean, reports Planet Today.
The team, led by microbiologist Qichao Tu from Shandong University, analyzed approximately 200 sediment samples and processed over five terabytes of genetic data. As a result, they identified 237 large viral genomes, some of which contained hundreds of thousands of DNA letters, comparable to the genetic material of living cells.
The discovered viruses fell into two categories. Two-thirds were giant viruses that infect single-celled algae and amoebas, while the remainder were giant phages that prey on bacteria and carry extensive genetic machinery for self-replication.
Eight viruses drew particular attention for not matching any known family. Researchers suggested they represent an entirely new branch within the order Imitervirales. Seven of these viruses were statistically linked to arthropods—crabs, shrimp, and insects—indicating a possible connection between giant viruses and animals, not just microbes.
One giant phage displayed remarkable stability: its genome, nearly 99.9% identical, was found in all samples from the port city of Qingdao, regardless of season or sampling depth. This points to its exceptional adaptability to the ever-changing conditions of mudflats, where tides shift twice daily.
An analysis of relationships between viruses and potential hosts showed that the strongest associations were with fungi and single-celled organisms, rather than with algae, as previously believed. Moreover, randomness played a greater role in virus distribution than chemical factors, though this pattern weakened in areas abundant with hosts.
Scientists identified hundreds of genes responsible for metabolizing DNA, amino acids, and sugars, which viruses can utilize after infecting a cell. Crucially, giant viruses carry genes linked to carbon cycling and nitrogen processing, directly impacting the chemical composition of coastal ecosystems.
Although it remains unproven whether these genes are activated during infection, their presence suggests a potential role for viruses in global biochemical cycles. The discovery presents new challenges for researchers: they must now determine which hosts these microorganisms infect and how significantly they alter coastal chemistry. One thing is clear: tidal flats, long overlooked by science, are teeming with unexpected life.
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