A phylogenomic and ecological analysis of the globally abundant Marine Group II archaea (Ca. Poseidoniales ord. nov.)

• DOI: 10.1038/s41396-018-0282-y
• Publication Date: 2018-10-15T07:46:03Z
• Authors: Christian Rinke; Francesco Rubino; Lauren F Messer; Noha Youssef; Donovan H Parks; Maria Chuvochina; Mark Brown; Thomas Jeffries; Gene W Tyson; Justin R Seymour; Philip Hugenholtz
• Keywords: Candidatus; Lineage (genetic); Horizontal Gene Transfer

Abstract Marine Group II (MGII) archaea represent the most abundant planktonic archaeal group in ocean surface waters, but our understanding of has been limited by a lack cultured representatives and few sequenced genomes. Here, we conducted comparative phylogenomic analysis 270 recently available MGII metagenome-assembled genomes (MAGs) to investigate their evolution ecology. Based on rank-normalised genome phylogeny, propose that is an order-level lineage for which name Candidatus Poseidoniales (after Gr. n. Poseidon, God sea), comprising families Poseidonaceae fam. nov. (formerly subgroup MGIIa) Thalassarchaeaceae MGIIb). Within these families, 21 genera could be resolved, many had distinct biogeographic ranges inferred nutrient preferences. Phylogenetic analyses key metabolic functions suggest ancestor Ca. was water-dwelling photoheterotroph evolved occupy multiple related ecological niches based primarily spectral tuning proteorhodopsin genes. Interestingly, this adaptation appears involve overwrite mechanism whereby existing single copy gene replaced horizontally transferred copy, instances should allow abrupt change light absorption capacity. Phototrophy lost entirely from five coinciding with deeper aphotic waters. We also report first nitrate reductase two acquired via horizontal transfer (HGT), potential oxygen limitation. Additional traits differentiating include flagellar-based adhesion, transporters, sugar, amino acid, peptide degradation. Our results HGT shaped variety become successful