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Cannibal virus `discovered` in Antarctica

Last Updated: Monday, April 11, 2011 - 10:48

Washington: Scientists claim to have
discovered a cannibal virus that "eats its own" and encourage
faster growth of the host algae population in Antarctica.

An international team, led by Prof Rick Cavicchioli
of University of New South Wales, has found the virus, called
Organic Lake Virophage or OLV, in a hypersaline lake near the
Davis station in the white continent, the `Proceedings of the
National Academies of Science` journal reported.

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", or PVs, that infect algae
and consequently help control algal blooms. Like Sputnik and
Mavirus, OLV`s genome includes genes that it collected from
the Organic Lake phycodnaviruses, confirming the predator-prey
relationship.

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.

While OLV was the dominant virophage in Organic Lake,
the team says that there are other related virophages present.

The scientists have also found genome sequences that
match OLV from nearby Ace Lake. And there may be many more
virophages waiting to be discovered.

PTI

First Published: Monday, April 11, 2011 - 10:48
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