Investigating virus-host interactions in a changing Arctic Ocean

The Arctic Ocean (AO) is changing at an unprecedented rate, with sea ice loss, warming and freshening affecting microbial community dynamics, including primary productivity. In the Arctic, primary production is driven by eukaryotic phytoplankton and one picoeukaryote in particular, Micromonas polaris, is ecologically dominant. Basic knowledge of the spatial variability and diversity of surface AO microbial eukaryotes, however, is limited. M. polaris is known to occur in a variety of different environments in the AO, yet its molecular diversity and mechanisms underlying its ecological success are not well understood. The AO is also a hotspot for giant virus diversity, and M. polaris is susceptible to infection by giant viruses known as Micromonas polaris viruses (MpoVs). Previous research has characterised MpoV infection dynamics and the potential for these to be affected by warming, yet genomic data, which would provide insight into MpoV diversity and the molecular basis for virus-host interactions, are lacking. Here, we first examine the phylogenetic structure and molecular diversity of microbial communities from contrasting environmental systems across the surface Beaufort Sea. We find significant variation between systems and a high degree of ecological specialisation among sea ice-associated communities, which we predict may be replaced with more generalist ones in future. Our analysis also highlights the abundance and phylotype diversity of the photosynthetic picoeukaryote M. polaris in AO microbial communities. Next, we present the pangenome of M. polaris, which reveals cryptic diversity within the species and provides genomic evidence in support of a mixotrophic lifestyle. We then compare MpoV genomes and show high diversity among MpoVs, including a cryptic strain and a novel virusencoded betaine/carnitine/choline transporter (BCCT). Finally, we examine the molecular mechanisms underlying virus-virus competitive interactions in a M. polaris-MpoV system and find strong evidence of coinfection and mutual interference by coinfecting viruses. This work contributes in depth phylogenetic and molecular perspectives on ecologically important Arctic specialists and their interactions in the context of a rapidly changing AO.<p></p>

Author dc:creator

• V Jackson (13958969)

• Arctic Ocean
• Phytoplankton
• Picoeukaryote
• Algavirales
• Pangenomics
• Biodiversity
• Marine microbiology
• Microbial ecology

Statement dc:rights

• All rights reserved
• Open Access after 2026-12-31

Identifier

10871/141100

OAI identifier oai:identifier

oai:figshare.com:article/29844434