eukaryogenesis Archives - Astrobiology

Diversity of virus-like particle morphotypes in Asgard archaeal enrichment cultures. Negativestain transmission electron microscopy revealed diverse virus-like particles in low abundance Asgard archaeal enrichment cultures, including contractile and non-contractile head-tail phage morphotypes (A), spindle virus morphotypes (B), putative elongated or prolate capsids (C), and decorated capsids (D). Some putative capsids were associated with short tail-like structures, representative of podovirus morphotypes (E). Long filamentous structures were identified, some potentially representing filamentous viruses (F). Numerous diverse, unidentified extracellular particles were also detected (G). Scalebar = 100 nm. -- biorxiv.org

Nomenclature, Systematics, Natural History

Viruses, Proviruses and Satellites from Asgard Archaea Enrichments Reveal Complex Microbial Interactions

by Keith CowingSeptember 9, 2026September 9, 2026

[biorxiv.org] Asgard archaea are the closest known relatives of eukaryotes and are central to models of eukaryogenesis involving archaeal–bacterial symbiosis, yet the contribution of viruses remains unexplored.

In December 2025, Brett Baker led a research cruise to collect microbial genomes off the coast of Uruguay. In this photo, Tyler Smith pilots a remotely operated vehicle collecting shallow coastal sediments. Credit: Brett Baker.

AI - Data - Apps - Cybernetics, Away Teams & Field Reports, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release, ROVs/Submersibles/Diving, Sample Return, Water/Hycean Worlds & Oceanography

A Break In A Longstanding Mystery About The Origin Of Complex Life

by Keith CowingFebruary 18, 2026February 18, 2026

The most widely accepted scientific explanation for the arrival of all complex life on Earth has had an unsolved mystery at its heart. According to the theory, all plants, animals […]

Iron disruption through endosymbiosis: An overview of disruptive effects of iron throughout endosymbiosis, from ecological associations and biochemistries of archaea and bacteria (69) to LECA (90, 94). These effects may underlie a mechanistic connection between the cessation of marine iron deposition and the radiation of the earliest eukaryotes. -- biorxiv.org

Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Origin & Evolution of Life, Status Report

Did Iron Suppress Eukaryote Emergence and Early Radiation?

by Keith CowingFebruary 5, 2026June 11, 2026

The last eukaryotic common ancestor (LECA) is widely thought to have been an oxygen-respiring organism, arising through endosymbiosis when a free-living bacterium became the mitochondrion.

Biochemical requirements and toxicities for oxygen, iron and sulfide restrict conditions for endosymbiosis: Iron, sulfide and oxygen readily react with one another, leading to reservoir fluctuations that characterize Paleoproterozoic marine chemistry. A narrower set of interactive conditions involving these three chemicals (dotted box) are circumscribed by the context of cellular homeostatic constraints, which differ among organisms. Iron is biphasic: it is essential at lower cellular concentrations but toxic at higher cellular concentrations. Iron and oxygen homeostatic constraints must have been operable within archaea and bacteria across the process of endosymbiosis, up to and including full endogenization of the mitochondrion into a eukaryotic organelle. -- biorxiv.org

Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Status Report

Did Iron Suppress Eukaryote Emergence and Early Radiation?

by Keith CowingJune 29, 2025June 28, 2025

The last eukaryotic common ancestor (LECA) is widely thought to have been an oxygen-respiring organism, arising through endosymbiosis when a free-living bacterium became the mitochondrion.

Distribution of Asgardarchaeota based on the recovery of MAGs from a wide variety of habitats. The ecological distribution of the Asgardarchaeota genomes across 12 environments, including genomes added by this study (purple star) and the total number of MAGs (yellow circle). The bar chart shows the number of MAGs from each lineage by environment, indicating lineages found only in a single environment (Atabeyarchaeia; teal triangle), circular complete genomes (black circle), and MAGs with known associated viruses or proviruses (blue phage). We note the novel class, Ranarchaeia, and recently described Asgardarchaeia in the legend with asterisks. Guaymas Basin is shown separately from the other bathypelagic-associated MAGs to showcase the increased genomic diversity from this site. -- biorxiv.org

Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Status Report

Oxygen Metabolism In Descendants Of The Archaeal-Eukaryotic Ancestor

by Keith CowingJuly 8, 2024July 7, 2024

Asgard archaea were pivotal in the origin of complex cellular life. Hodarchaeales (Asgardarchaeota class Heimdallarchaeia) were recently shown to be the closest relatives of eukaryotes. However, limited sampling of these […]