Seasonal Dynamics of Algae-Infecting Viruses and Their Inferred Interactions with Protists

Abstract

Viruses are a highly abundant, dynamic, and diverse component of planktonic communities that have key roles in marine ecosystems. We aimed to reveal the diversity and dynamics of marine large dsDNA viruses infecting algae in the Northern Skagerrak, South Norway through the year by metabarcoding, targeting the major capsid protein (MCP) and its correlation to protist diversity and dynamics. Metabarcoding results demonstrated a high diversity of algal viruses compared to previous metabarcoding surveys in Norwegian coastal waters. We obtained 313 putative algal virus operational taxonomic units (vOTUs), all classified by phylogenetic analyses to either the Phycodnaviridae or Mimiviridae families, most of them in clades without any cultured or environmental reference sequences. The viral community showed a clear temporal variation, with some vOTUs persisting for several months. The results indicate co-occurrences between abundant viruses and potential hosts during long periods. This study gives new insights into the virus-algal host dynamics and provides a baseline for future studies of algal virus diversity and temporal dynamics.

A persistent giant algal virus, with a unique morphology, encodes an unprecedented number of genes involved in energy metabolism

“…This fits well with the two multi-species infecting haptophyte viruses, PkV RF01 and HeV RF02, that have reduced proportions of infectious particles and longer replication times (33), relative to other haptophyte viruses with restricted host ranges. In the ocean, persistent relationships—such as between PkV RF01 and its hosts—seem to be most common among viruses infecting unicellular algae; this has been demonstrated by several metabarcoding studies revealing the persistence of dominance of viral OTUs over several months (Gran-Stadniczeñko et al, 2019; Johannessen et al, 2017).…”

Year-round dynamics of amplicon sequence variant communities differ among eukaryotes,Mimiviridae, and prokaryotes in a coastal ecosystem

“…Previous studies have explored the temporal dynamics of eukaryotic (4–6), prokaryotic (1, 7) (8–11), both eukaryotic and prokaryotic (12, 13), and viral communities (14). Other studies have investigated co-variations among these cellular communities (15–17) or cellular and viral communities (18–24). Overall, these studies have revealed similarities and differences in community dynamics among different microbe groups.…”

“…A recent study revealed an association between eukaryote communities and Mimiviridae in a global metagenomic dataset (32). Another study detected cooccurring pairs of eukaryotes and large DNA viruses including members of the Mimiviridae through time-series sampling for more than 1 year in Northern Skagerrak, South Norway (18). These spatial and temporal associations highlight the tight ecological interactions between diverse Mimiviridae and eukaryotes, that is, the obvious dependance of Mimiviridae replication on the activity of their hosts and the possible top-down regulatory roles of these viruses on the dynamics of the host community as a consequence of lytic infection.…”

An Optimized Metabarcoding Method for Mimiviridae

“…These numerical features and the wide host ranges of Mimiviridae suggest that they are one of the key players in marine microbial ecosystems. However, little is known about their community structures and dynamics in different environments [18].…”

“…Effective methods for the characterization of the community structures of Mimiviridae and related viruses have been the amplification and sequencing (i.e., "meta-barcoding") of highly conserved genes such as the major capsid protein genes, DNA polymerase family B (polB) and DNA mismatch repair protein genes [10,[18][19][20][21]. Recently, Li et al proposed a novel meta-barcoding method (i.e., the MEGAPRIMER method) to investigate Mimiviridae diversity and revealed a hitherto unknown level of Mimiviridae richness in environmental samples [22,23].…”