Sukunaarchaeum Mirabile - smallest archaeal genome

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TL;DR

Sukunaarchaeum Mirabile
ribosomal machinery, metabolis, dependant ipon a host --? somewhere between a virus and a living cell

Is it a virus that can make it's own proteins; or a cell that lacks ability to metabolize.
Newly discovered 2024

Specific Characteristics of Sukunaarchaeum Mirabile​

• Smallest Archaeal Genome: This microorganism has about 283,000 base pairs. This is far smaller than typical archaea. Such extreme reduction strips away most metabolic genes while still keeping essential ones.
• Extreme Dependency: It cannot perform its own metabolism. This means it must borrow almost everything from its host to survive. This makes it functionally like a parasite but still more complex than a virus.
• Notable Ribosome Retention: Moreover, unlike viruses, this organism encodes ribosomes and messenger RNA machinery, allowing it to make proteins. This is a key trait of cellular life. It blurs the virus–cell divide.

For more information:
https://www.profolus.com/topics/suk...red-organism-exists-between-life-and-nonlife/

https://www.biorxiv.org/content/10.1101/2025.05.02.651781v1.full.pdf
Abstract Defining the minimal genetic requirements for cellular life remains a fundamental question in biology. Genomic exploration continually reveals novel microbial lineages, often exhibiting extreme genome reduction, particularly within symbiotic relationships. Here, we report the discovery of Candidatus Sukunaarchaeum mirabile, a novel archaeon with an unprecedentedly small genome of only 238 kbp —less than half the size of the smallest previously known archaeal genome— from a dinoflagellate-associated microbial community. Phylogenetic analyses place Sukunaarchaeum as a deeply branching lineage within the tree of Archaea, representing a novel major branch distinct from established phyla.

 

[BillTre]

This is interesting an article, but the conclusions about it being between living and non-living or between cells and viruses is kind of a stretch.
To me it seems more like a different kind of symbiotic organelle. Mitochondria and chloroplasts are the best know of these, but there are others. Symbionts will generally have a genome reduction and increased dependence on the host cell for may metabolic purposes.
Here are some posts I made on PF about these kinds of things.

1. Symbiont involved in processing nitrate to nitrogen, here
2. Possible origin of mitochondria, here

There can be more then one symbiont in a cell, for example plant cells with mitochondria and chloroplasts.

Extreme dependency and loss of metabolic capacity are things that parasites can do. There are plenty of parasites that largely live in other cells. Pseudoloma neurophilia parasites are an example in fish (which I am familiar with).
In cases of symbionts, there is usually a reason for the host cell to keep the symbiont around (there are cases or mitochondria degenerating into hydrogenosome (little bits of mitochondria with reduced metabolic capacities). It would be interesting to find out what benefti the host cell is deriving from the Sukunaarchaeum mirabile entity.