The virus is only the third “virophage” discovered. The first one, called Sputnik, was discovered in 2008 and the second one, Mavirus, was discovered earlier this year.

Viruses reproduce by infecting host cells and using cell’s molecular machinery to make multiple copies of their own genome and to package these genomes into protein shells. A virophage is different in that it targets a host cell that is already infected by a “regular” virus.

Prof Cavicchioli’s team found OLV associated with a group of giant “phycodnaviruses” (PV), that infect algae and consequently help control algal blooms.   The discovery of a virophage in Organic Lake adds new complexity to the dynamics of the microbial community in the Antarctic system, says Prof Cavicchioli whose team modelled the impact of OLV as a predator in the marine system.

“By reducing the number of PVs in the community, OLV shortens the time it takes for the host algae population to recover.

Modelling shows that the virophage stimulates secondary production through the microbial loop by reducing overall mortality of the host algal cell after a bloom, and by increasing frequency of blooms during the summer periods.

“Antarctic lake systems have evolved mechanisms to cope with long light-dark cycles and a limited food web. In Organic Lake and similar systems, a decrease in PV activity may be instrumental in maintaining the stability of the microbial food web,” he said.