Hikarchaeia demonstrate an intermediate stage in the methanogen-to-halophile transition

Joran Martijn, Max E. Schön, Anders E. Lind, Julian Vosseberg, Tom A. Williams, Anja Spang, Thijs J.G. Ettema*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Halobacteria (henceforth: Haloarchaea) are predominantly aerobic halophiles that are thought to have evolved from anaerobic methanogens. This remarkable transformation most likely involved an extensive influx of bacterial genes. Whether it entailed a single massive transfer event or a gradual stream of transfers remains a matter of debate. To address this, genomes that descend from methanogen-to-halophile intermediates are necessary. Here, we present five such near-complete genomes of Marine Group IV archaea (Hikarchaeia), the closest known relatives of Haloarchaea. Their inclusion in gene tree-aware ancestral reconstructions reveals an intermediate stage that had already lost a large number of genes, including nearly all of those involved in methanogenesis and the Wood-Ljungdahl pathway. In contrast, the last Haloarchaea common ancestor gained a large number of genes and expanded its aerobic respiration and salt/UV resistance gene repertoire. Our results suggest that complex and gradual patterns of gain and loss shaped the methanogen-to-halophile transition.

Original languageEnglish
Article number5490
JournalNature Communications
Issue number1
Publication statusPublished - Dec 2020

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