Departmental Seminar – 18 April

This week the Department welcomes Dr. Stephen Short from the Department of Biology, University of Toronto:

The Complex and Enigmatic World of Freshwater Algal Viruses


As well as being agents of infectious disease, it is now widely accepted that viruses are intimate partners in life that have shaped the evolution of cellular organisms and have played an ongoing role in Earth’s biogeochemistry. With respect to the latter, the discovery almost 30 years ago that viruses infected marine and freshwater primary producers, including species of eukaryotic algae, contributed to the emergence of virology as its own discipline within aquatic sciences. My research program is centered on freshwater algal viruses with the broad goal to understand how they influence aquatic primary production and food web processes. To that end, my students and I have explored freshwater algal virus ecology by studying their biodiversity and seasonal dynamics, persistence in the environment, and relative importance to phytoplankton mortality. We have learned that diverse algal viruses can be found in various freshwaters, but as in marine environments, freshwater algal virus communities are surprisingly dominated by a single group. We have also discovered that algal viruses can form seasonally persistent ‘seedbanks’, and some can overwinter in a frozen pond remaining infectious until their host abundances reach levels we presume are necessary for ongoing virus production. Additionally, the fact the we were able to detect diverse viruses in Lake Erie sediments suggests that sediments are an important refugium that could allow some phytoplankton virus to escape seasonal bottlenecks when they suffer high rates of destruction. With respect to our studies of virus-mediated mortality, we have developed experimental methods to examine phytoplankton mortality at a species, or taxon level. An unexpected finding from this work was the observation that in some cases, viruses appeared to counteract the effects of grazing mortality by stimulating an alga’s growth, perhaps through the liberation of resources from other lysed cells, or by reducing competition. Finally, an additional focal point of my research program is our isolation and ongoing characterization of a newly discovered algal virus. Molecular characterizations of this virus in the lab and field have revealed its complex evolutionary history as well as its puzzling ecological dynamics. Overall, my research has helped demonstrate that, despite their furtive nature and borderline status as ‘living’ microorganisms, freshwater algal viruses are critically important members of freshwater ecosystems.

This seminar will be held in Room 1102, Biosciences Complex, from 11:30-12:30pm. Free meet & greet pizza lunch after the seminar from 12:30-1:30PM in the 3rd floor lunch room (3406).

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