Ocean algae get 'coup de grace' from viruses
Viruses don't immediately kill algae but live in harmony with them

Date:
September 15, 2020
Source:
Rutgers University
Summary:
Scientists have long believed that ocean viruses always quickly
kill algae, but new research shows they live in harmony with
algae and viruses provide a 'coup de grace' only when blooms
of algae are already stressed and dying. The study will likely
change how scientists view viral infections of algae, also known
as phytoplankton - especially the impact of viruses on ecosystem
processes like algal bloom formation (and decline) and the cycling
of carbon and other chemicals on Earth.



FULL STORY ========================================================================== Scientists have long believed that ocean viruses always quickly kill
algae, but Rutgers-led research shows they live in harmony with algae
and viruses provide a "coup de grace" only when blooms of algae are
already stressed and dying.


==========================================================================
The study, published in the journal Nature Communications, will likely
change how scientists view viral infections of algae, also known as phytoplankton - - especially the impact of viruses on ecosystem processes
like algal bloom formation (and decline) and the cycling of carbon and
other chemicals on Earth.

"It's only when the infected algal cells become stressed, such as when
they run out of nutrients, that the viruses turn deadly," said lead author Benjamin Knowles, a former post-doctoral researcher in the Department of
Marine and Coastal Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick who is now at UCLA. He was
also a post- doctoral fellow at Rutgers' Institute of Earth, Ocean, and Atmospheric Sciences. "We feel that this entirely new model of infection
is widespread in the oceans and stands to fundamentally alter how we
view host-virus interactions and the impact of viruses on ecosystems and biogeochemical cycling since it goes against the long-accepted classic
model of viruses always being lethal and killing cells." Biogeochemical cycling refers to essential nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, iron and water circulating through organisms and
the environment. The coccolithophore algae Emiliania huxleyi was the
focus of the study as a model for other algae-virus systems and is a
central driver of this process.

The scientists studied virus-algae interactions in the lab and in
controlled, mini-blooms in coastal waters of Norway. They focused on
viral infection of a form of algae that is responsible for generating
much of the oxygen and carbon cycling on Earth. A group of ocean viruses
called coccolithoviruses routinely infect and kill E. huxleyi over 1,000
square miles, which is viewable from space via Earth-observing satellites.

The viruses eventually rupture algal cells, contributing to the global
food web by making energy and organic matter available to other
organisms. But infected cells don't die right away, the scientists
discovered. Instead, infected cells multiply and bloom across dozens of
miles of ocean waters and die in a coordinated manner. These dynamics have
been routinely observed in previous studies but couldn't be explained by
the rate at which algal hosts and viruses encounter each other in nature.

"The algae and viruses have a quasi-symbiotic type of relationship,
allowing both algal cells and viruses to replicate happily for a while,"
said senior author Kay D. Bidle, a professor and microbial oceanographer
in the Department of Marine and Coastal Sciences at Rutgers-New Brunswick
and the Institute of Earth, Ocean, and Atmospheric Sciences. "We feel
that these newly discovered dynamics also apply to other virus-algal interactions across the oceans and are fundamental to how infection
works. By combining experimental, theoretical and environmental
approaches, our work presents a template to diagnose this type of
infection in other systems." The algae-virus dynamics have important implications for the outcome of infections and the flow of carbon and may
lead to scenarios where carbon dioxide is sequestered, or stored, in the
deep ocean rather than retained in the upper ocean, Bidle said. Further research is needed to fully understand the extent of these dynamics and
their impacts on ecosystems and the cycling of carbon in the oceans.


========================================================================== Story Source: Materials provided by Rutgers_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Ben Knowles, Juan A. Bonachela, Michael J. Behrenfeld, Karen
G. Bondoc,
B. B. Cael, Craig A. Carlson, Nick Cieslik, Ben Diaz, Heidi
L. Fuchs, Jason R. Graff, Juris A. Grasis, Kimberly H. Halsey,
Liti Haramaty, Christopher T. Johns, Frank Natale, Jozef
I. Nissimov, Brittany Schieler, Kimberlee Thamatrakoln, T. Frede
Thingstad, Selina Vaage, Cliff Watkins, Toby K. Westberry, Kay
D. Bidle. Temperate infection in a virus-host system previously
known for virulent dynamics. Nature Communications, 2020; 11 (1)
DOI: 10.1038/s41467-020-18078-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200915090110.htm

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