A colossal virus, named PelV-1, has been discovered in the Pacific Ocean, significantly expanding the known diversity and capabilities of viruses. This giant virus measures approximately 2.3 micrometers in length, making it one of the longest viruses ever recorded. Its capsid alone is about 200 nanometers in diameter, substantially larger than most viruses. PelV-1 is characterized by an exceptionally long, slender tail, approximately 30 nanometers wide, and a shorter, thicker appendage, contributing to its unique morphology.
PelV-1 infects a type of phytoplankton called Pelagodinium, a vital component of marine ecosystems. Unlike most tailed viruses that target bacteria, PelV-1's infection of phytoplankton, coupled with its immense tail, has garnered significant scientific interest. The virus's genetic makeup includes genes associated with metabolism, light-harvesting systems, sugar transporters, and water channels, suggesting PelV-1 may influence its host's behavior and functions beyond basic metabolic processes. Researchers observed that PelV-1 uses its elongated tail for host entry, and the tail disappears after infection, indicating a specialized role in the initial stages of the infection cycle. This discovery adds to the growing understanding of giant viruses, first identified in 2003, which are known for their large size and complex genomes, and their significant impact on marine ecosystems by influencing protist survival and controlling phytoplankton populations.