Sputnik, which was first discovered in the water-cooling tower in Paris in 2008, was the first virophage ever identified. Earlier this month, Matthias Fischer and Curtis Suttle announced the discovery of a second virophage known as Mavirus.
The discovery of OLV makes this only the third virophage, though there is evidence of sequence matches to OLV in numerous other locations including the nearby Ace Lake. However, the other matches span the globe, including a lagoon in the Galapagos Islands, a bay in New Jersey, and a freshwater lake in Panama.
Virophages, which are known as virus eaters, attack other viruses, as is the case with the first virophage, Sputnik. Unable to multiply within a host, virophages rely on hosts infected with other viruses. In the case of Sputnik, it was an amoeba infected with a mamavirus. Sputnik would essentially take over the replication process of the mamavirus. Because of this takeover, the mamavirus is unable to produce properly, thus reducing its ability to infect the amoeba.
The new OLV genome was discovered within the sequences of phycodnaviruses. Phycodnaviruses are a group of large viruses that attack algae. The OLV targets these phycodnaviruses, allowing the algae in the lake to survive and bloom during the summer months.
The team’s discovery, and the discovery of connected sequences in other locations around the globe, opens the door for the possible discovery of many more virophages. The study of these virus eaters is just beginning and holds promise of a better understanding of the complexity of biological function within these viruses.
More information: Sheree Yau et al., Virophage control of antarctic algal host–virus dynamics, Published online before print March 28, 2011, Proceedings of the National Academies of Sciences doi:10.1073/pnas.1018221108
