Asgardarchaeota – A Novel Prokaryotic Group Discovered in Aquatic Sediments that Might Shed Light on the Origin and Early Evolution of Eukaryotes.

Abstract

The origin of the eukaryotic cell and its shared evolutionary history with Archaea are among the hottest topics in modern biology. Recent improvements in culture-independent genomics and phylogenomic analyses provided compelling evidence in support of the emergence of eukaryotes from within the Archaea. An important step towards revealing the identity and nature of the archaeal ancestor was made following metagenomics-based discovery of the Asgardarchaeota superphylum, a group of uncultivated archaea consisting of Loki-, Thor-, Heimdall- and Odinarchaeia. Their recognition as the closest extant relatives of the eukaryotes has reignited a decades-old debate regarding the topology of the Tree of Life. Moreover, genomic investigations of Asgardarchaeota revealed a plethora of “Eukaryote Signature Proteins” (ESPs), previously thought to be unique to eukaryotes, which may help shed light on the molecular events in early eukaryogenesis. In this work, we briefly review current knowledge about the geographical distribution, phylogeny, ESP content and metabolic capabilities of the highly diverse Asgardarchaeota in an attempt to picture the lifestyle and early evolution of eukaryotes.

Keywords

• aquatic sediments
• Asgardarchaeota
• eukaryogenesis
• eukaryote signature proteins