Aureococcus anophagefferens (Pelagophyceae) genomes improve evaluation of nutrient acquisition strategies involved in brown tide dynamics

Abstract

The pelagophyte Aureococcus anophagefferens causes harmful brown tide blooms in marine embayments on three continents. Aureococcus anophagefferens was the first harmful algal bloom species to have its genome sequenced, an advance that evidenced genes important for adaptation to environmental conditions that prevail during brown tides. To expand the genomic tools available for this species, genomes for four strains were assembled, including three newly sequenced strains and one assembled from publicly available data. These genomes ranged from 57.11 to 73.62 Mb, encoding 13,191–17,404 potential proteins. All strains shared ~90% of their encoded proteins as determined by homology searches and shared most functional orthologs as determined by KEGG, although each strain also possessed coding sequences with unique functions. Like the original reference genome, the genomes assembled in this study possessed genes hypothesized to be important in bloom proliferation, including genes involved in organic compound metabolism and growth at low light. Cross‐strain informatics and culture experiments suggest that the utilization of purines is a potentially important source of organic nitrogen for brown tides. Analyses of metatranscriptomes from a brown tide event demonstrated that use of a single genome yielded a lower read mapping percentage (~30% of library reads) as compared to a database generated from all available genomes (~43%), suggesting novel information about bloom ecology can be gained from expanding genomic space. This work demonstrates the continued need to sequence ecologically relevant algae to understand the genomic potential and their ecology in the environment.

“Quasigenus” amongPhycodnaviridae: A diversity of chlorophyte-infecting viruses in response to a dense algal culture in a high-rate algal pond

“…Alga strains within one alga species can be virus susceptible or resistant ( e . g ., with the system of Aureococcus anophagefferens and AaV (Gobler et al, 2007; Brown and Bidle, 2014; Gann et al, 2022)), thereby a dense culture with different strains could support a group of closely related viruses (the “quasigenus”) that are capable of infecting some (one or more) strains of an alga species and not others. It will be interesting to determine if this “quasigenus” phenomenon also happens so prominently during algal blooms in natural environments or if it meets only in the very favourable conditions of the HRAP.…”

The diel disconnect between cell growth and division inAureococcusis interrupted by giant virus infection

“…anophagefferens (Gann et al, 2022). Such heterogeneity in gene expression among control samples is compelling and indicates that cells in non-synchronous infections are transcriptionally and metabolically distinct at different times of day.…”

Kratosvirus quantuckense: the history and novelty of an algal bloom disrupting virus and a model for giant virus research

“…Of specific note, blooms can occur at points when dissolved organic nitrogen levels are high ( Laroche et al, 1997 ) and when inorganic nutrients are low ( Keller and Rice, 1989 ), as summarized by Gobler et al (2002) . Utilization of many forms of organic nitrogen has been verified in culture ( Berg et al, 2002 ; Gann et al, 2022 ) and transporters specific for nucleosides, oligopeptides, and purines in the algal genome suggest the capability of diverse nitrogen species assimilation when inorganic nitrogen is depleted ( Gobler et al, 2011 ). Additionally, dissolved organic carbon consumption may also be important during the growth stage of a bloom ( Gobler et al, 2002 , 2004 ).…”

“…This superfamily includes proteins that degrade carbohydrates of algae and plants including xylan and alginate. Various algae are also a source of lectin/glucanases used in biomedical research and three strains of A. anophagefferens encode for a potential lectin/glucanase as well ( Gann et al, 2022 ). This may highlight a point of origin for the presence of these lectin/glucanases in the viral genome.…”