Numerous studies have shown that viruses are present in a variety of environments on Earth, acting as drivers of biogeochemical cycles and powerful selective forces. Among them, giant viruses of amoebae have garnered attention from the scientific community due to their large particles and extensive genomes. Here, we describe the discovery of one of the largest tailed viruses in the known virosphere (averaging 1350 nm), named Naiavirus. This virus, isolated from a swamp biome in Brazil, has particles with a never-before-seen morphology and composition, and represents the first giant amoeba virus with an external envelope covering the capsid and extending over a flexible tail region. The Naiavirus genome, with nearly 1 million base pairs, reveals a unique set of genes, and does not resemble any other virus previously isolated so far.
© 2025. The Author(s).