Seasonal and evolutionary patterns of planktonic Hikarchaeia reveal ecological niches of marine rare biosphere constituents.

Hikarchaeia, a group of uncultivated Archaea, exhibit distinct seasonal and vertical distribution patterns, with relative abundance peaking at ~1% of prokaryotic amplicons in the North Atlantic Gyre.

• Why it matters: Understanding the ecology of these enigmatic microbes is crucial as ocean conditions change due to warming, affecting biogeochemical cycles and the marine rare biosphere.
• What they did: Researchers performed 5 years of monthly sampling, sequencing 16S rRNA genes, and metagenomes, recovering a complete 1.17 Mbp genome and identifying five phylogenomic clades with habitat partitioning.
• The result: Findings reveal niche partitioning among Hikarchaeia clades, seasonal abundance linked to ocean stratification, and potential roles in nitrogen and carbon cycling, aiding models of marine microbiomes.