Supervised by:

Alexander Culley (Regular Member (Co-researcher))

Research project description

Characterization and ecology of the High-Arctic Nucleocytoviricota

Introduction

Ecosystems of the High Arctic are today in the spotlight of the environmental scientific community. At the forefront of the effects of global change and global warming, the ecosystems of the Arctic cryosphere are at risk of disappearing from the global biosphere soon, leading to a huge loss of biocenosis and unique biotopes often still unknown. For example, the viral communities of the far north are still largely uncharacterized despite the indispensable role they play. In addition to being key elements in biogeochemical cycles and in the evolution of organisms, viruses are involved in energy transfer and regulation of ecosystems on a microbial scale. In polar environments, where the microorganisms comprise the largest biomass, viral activity can be a crucial regulatory factor in the dynamics and composition of communities.

Objectives

The primary objective of this project is to characterize a specific fraction of the viral communities of the far north, the Nucleocytoviricota, in a context of rapid environmental changes. This viral phylum includes all families of nucleocytoplasmic viruses with large DNA genomes (NCLDVs), also called large and giant viruses. These viruses have the particularity of infecting only eukaryotic cells and have a very large genome that codes for hundreds, if not thousands, of metabolic genes, some of which are involved in nutrient absorption, glycolysis or the TCA cycle. Recent studies have revealed that NCLDVs are especially endemic in polar aquatic environments (Endo et al., 2020)⁠ and that they play a key role in the evolution of micro-eukaryotic communities and the functioning of biogeochemical cycles.

Study Sites

In order to characterize this viral fraction, different ecosystems will be studied in the vicinity of the Ward Hunt Island Station (85°05 N, 74°10 W). Located at the northern tip of Canada, off the north coast of Ellesmere Island and in the Quttinirpaaq National Park, the island and its environs feature lakes, ice shelves, fjords and an epishelf lake.

Material and methods

The analysis of the taxonomic and functional diversity of Nucleocytoviricota will be assessed using an initial metagenomic and bioinformatics approach based on open water samples and microbial biofilms. Analyses of the water samples will be conducted using metagenomes constructed in previous studies from the study area. For the microbial biofilm analyses, sampling will be conducted on the periphery of Ward Hunt Lake and the remnants of the Ward Hunt Island ice shelf adjacent to the island. Back at the laboratory, nucleic acids will be extracted, purified and sequenced. In addition, samples will be collected from our sampling sites for the isolation and cultivation of NCLDV-host systems.

Expected results

The identification followed by taxonomic and functional annotation of the viral sequences of Nucleocytoviricota will illustrate the great diversity of NCLDVs in these ecosystems. Particular attention will be paid to the identification of accessory metabolic genes that affect infection efficiency and involved in biogeochemical cycles. If such genes are identified, it would then be possible to express them in situ in order to understand their precise function and influence. Finally, once a virus-host system is brought into culture, I intend to conduct a series of experiments to test the effects of changes in environmental parameters related to climate change on the dynamics of infection.