endosymbiosis Archives

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.

Simplified EPOC generation and processing pipeline

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

Dominant Contribution Of Asgard Archaea To Eukaryogenesis

by Keith CowingJanuary 26, 2026January 26, 2026

The origin of eukaryotes is one of the key problems in evolutionary biology. The demonstration that the last eukaryotic common ancestor (LECA) already contained the mitochondrion—an endosymbiotic organelle derived from […]

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.

Bright field microscopic image corresponding to pTERF image showing control S. cerevisiae cox 2-60, and chimeras S. cerevisiae cox2-60-SynJEC3, S. cerevisiae cox2-60-SynBD2, S. cerevisiae cox2-60-SynBD3 and S. cerevisiae cox2-60-SynBD8. Marged image of bright field chimeric cells (at gray) and pTIRF (X100) microscopic images can be predicted using 561 nm laser for visualization of endosymbiont autofluorescence chlorophyl (in red Em.=653/95 nm) from photosynthetically enabled engineered Syn. No such signal was detected from control yeast cells. SP8 Fluorescent confocal microscopic (x63) image of control S. cerevisiae cox 2–60, and endosymbiontic chimera. Marged images: host cell was stained using Conn A-FITC (emission at 510–520 nm wavelength, in green) and cyanobacterial autofluorescence can detected at 616-650 nm wavelength range. The experiment was repeated three times independently with similar results. -- Nature

Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release

New Insight Into Chloroplast Evolution

by Keith CowingDecember 12, 2024December 12, 2024

One of the most momentous events in the history of life involved endosymbiosis — a process by which one organism engulfed another and, instead of ingesting it, incorporated its DNA […]

Evolution and function of the nitroplast - Multiple organelles in eukaryotic cells, including mitochondria, chloroplasts, and nitroplasts, evolved from the integration of endosymbiotic bacteria. In Braarudosphaera bigelowii, the chloroplast fi xes inorganic carbon to produce glucose, which feeds the respiratory chain in mitochondria that produces adenosine triphosphate (ATP), which in turn fuels nitrogen fi xation in the nitroplast. Glucose, ammonia, and ATP generated by the organelles, together with externally incorporated compounds (phosphorous, mineral nutrients, and vitamins), are the building blocks for cell metabolism, resulting in cell growth and division. -- Science

Biochemistry & Organic Chemistry, Biophysics, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release

The Nitroplast Revealed: A Nitrogen-fixing Organelle In A Marine Alga

by Keith CowingApril 20, 2024April 20, 2024

A nitrogen-fixing bacterial endosymbiont of marine algae is evolving into a nitrogen-fixing organelle, or nitroplast, according to a new study, thereby expanding a function that was thought to be exclusively […]

A light microscopy image shows the marine haptophyte algae Braarudosphaera bigelowii with a black arrow pointing to the nitroplast organelle. (Photo credit: Tyler Coale)

Biophysics, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Plant Biology, Press Release

The First Known Nitrogen-fixing Organelle

by Keith CowingApril 12, 2024April 12, 2024

Modern biology textbooks assert that only bacteria can take nitrogen from the atmosphere and convert it into a form that is usable for life. Plants that fix nitrogen, such as […]