Salty viruses balance ocean, says scientist

by Andy Poon
Staff writer

Many people would be surprised to learn that the earth's oceans teem with between 10 to 100 million viruses in every teaspoonful of seawater. That discovery was made a decade ago by a graduate student in the lab in which UBC microbiologist and oceanographer Curtis Suttle was doing post-doctoral work.

"The timing of the discovery really focused attention on the fact that micro-organisms are extremely important," says Suttle, now an associate professor in the departments of Earth and Ocean Sciences, Botany, and Microbiology and Immunology.

Two years after he witnessed the groundbreaking discovery by Lita Proctor in microbial ecologist Jed Fuhrman's lab at the State University of New York at Stony Brook, Suttle started his own research into finding out why viruses exist in such high numbers in the sea and what roles they play in marine and global ecosystems.

"Lita's work looked at viruses that infected bacteria in the ocean so I decided to look at viruses that affect photosynthetic organisms in the ocean," he says.

Suttle's research to date has revealed that indeed viruses play a major role both as destructive disease-causing agents and as part of the control mechanisms of the seas.

His research into how marine viruses infect and kill phytoplankton -- the tiny photosynthesizing organisms that form the base of the food web in the ocean -- showed that viruses have a tremendous impact on these ecologically important groups.

While Suttle proved that viruses can reduce the production of organic carbon, he has also studied how they can aid the release of organic matter into the oceans. His work revealed that carbon -- the common currency of plankton and all other living things -- is not always directly transferred from one organism to another through consumption. A large amount is released directly into the sea by bacterioplankton killed by viruses. This released carbon is then incorporated by other bacteria and lost through respiration.

"As much as 25 per cent of all living carbon in the oceans goes through viruses," he says.

As head of the Molecular Marine Microbiology and Virology Lab, Suttle and his team of a dozen researchers and students are working hard to broaden understanding of marine viruses.

But while viruses have been mainly thought of as pathogens, Suttle says they also play an essential part in the normal running of marine ecosystems.

His experiment in selectively removing viruses from seawater showed that instead of a rise in the growth of the remaining planktonic organisms, the plankton stopped growing completely. It demonstrated that the living organisms depend on the nutrients released as other organisms are killed by the viruses, thus illustrating the vital control mechanism that viruses play in marine ecosystems.

Suttle says the legacy of excellent research by his faculty colleagues -- the Oceanography group celebrated its 50th anniversary this fall -- and the availability of bright and motivated graduate students was a major factor in his decision to relocate his lab here from the University of Texas.

On top of that, UBC is his alma mater -- he completed both his undergraduate and doctorate degrees here.

"It's funny, I am actually in the same office as when I was a grad student here," he laughs. "So I guess you can say I have come full circle."