'Giant virus' found in the Pantanal is unlike any other seen before

Written by Felipe Alves da Silva

Published 27/09/2025 às 16:25

Researchers identify the Naiavirus in the waters of the Paraguay River, in the Pantanal.

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FAPESP Agency – Researchers have identified a new virus in the waters of the Paraguay River, considered the largest tailed virus ever described by science. Dubbed Naiavirus, the "microscopic giant" measures about 1.350 nanometers (nm)—common ones measure between 20 and 200 nm.

Very different from pathogens that cause disease in humans, such as influenza or coronavirus, Naiavirus infects only amoebas. In addition to its unusual size, it has a body surrounded by a kind of "mantle" and a flexible tail that bends and elongates, functioning as a tool to approach amoebas and facilitate infection.

The new virus has an immense genome: nearly 1 million base pairs of DNA. Many genes bear no resemblance to anything previously recorded by science, with functions previously believed to exist only in complex cells, such as bacteria and eukaryotes. Some resemble plant proteins. This suggests they may be involved in evolutionary processes that science has yet to understand. Their description was published in the scientific journal Nature Communications. on September 17th.

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The work, led by Jonathan Abraham, from the Institute of Biological Sciences of the Federal University of Minas Gerais (ICB-UFMG), was supported by FAPESP (projects 21/05519-0 e 24/13116-1). In addition to the UFMG group, researchers from the National Laboratory of Biosciences of the National Center for Research in Energy and Materials (LNBio-CNPEM), the Federal University of Rio de Janeiro (UFRJ), the São Paulo State University (Unesp), the Oswaldo Cruz Foundation (Fiocruz), Virginia Tech (USA) and the São Carlos Institute of Physics of the University of São Paulo (IFSC-USP) participated in the investigation.

According to the scientists responsible for the discovery, the supervirus proteins originate from a very ancient divergence, close to the emergence of life on Earth. "They could open new avenues for research and be used to produce drugs and enzymes of biotechnological interest," they told the IFSC-USP Press Office. Otavio Thiemann, one of the study's authors. "Furthermore, they can contribute to clarifying fundamental questions in biology, such as the process of eukaryogenesis, the formation of nuclei in primitive eukaryotic cells," he emphasized.

The research group analyzed 439 water samples until finding signs of the virus in one of them, collected in the municipality of Porto Murtinho (MS).

The article Naiavirus: an enveloped giant virus with a pleomorphic, flexible tail can be read clicking here.

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'Giant virus' found in the Pantanal is unlike any other seen before

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