A tiny cell hidden in a marine plankton today upsets the foundations of biology. Called Sukunaarchaeum Mirabile, this microscopic entity blurred the border, already fragile, between what is alive and what is not really. An unprecedented biological case that leaves researchers perplexed… and fascinated.
An unexpected discovery that calls into question the basics of biology
It all starts with a genetic anomaly identified in theADN Du Plancton harp regius. Researchers, in the midst of its bacterial symbiotes, detect a Unknown DNA loopabsent from all databases. Very quickly, they realize that they put their finger on a Organism never observed previously.
Baptized Sukunaarchaeum amazingthis microorganism lives in parasite within the plankton. However, it is neither like a bacteria or a virus. In reality, he seems to occupy a Unexplored gray area Between the two.
An ultra reduced genome, dedicated exclusively to survival
One of the most surprising elements is the genome size of this cell. He only counts 238,000 base pairsmuch less than some giant viruses. This figure is exceptionally low for a cell, even parasitic.
This tiny genome does not contain No identifiable metabolic route. In other words, Sukunaarchaeum produces neither energy nor nutrients by himself. On the other hand, it keeps the genes necessary for three key functions: DNA replicationits transcription into RNA, and the protein translation.
Thanks to this extreme reduction strategy, it focuses only on the essentials: reproduce. This is why researchers describe it as a cell at minimalist operationbut formidably effective.
No virus or classic cell: a parasite with biological UFOs
What makes Sukunaarchaeum so fascinating is its double nature. On the one hand, he has ribosomesfrom theMessenger RNAand can make its own proteins. These elements are typical of living cells, and absent in viruses. On the other, he depends completely on his host for all his other vital functions.
“In our study, zombie cells represent up to 10 % of all sea cells”underlines the researcher.
Therefore, it occupies a position unique intermediary. He can reply without the direct help of the host’s machinery, but he cannot survive without him. This biological contradiction raises a fundamental question: Can we still speak of a living cell ?
The analyzes indicate that it is up to the group of archaeathese ancient microbes from which the eukaryotes come (animals, plants, humans). However, it does not look like anything we have known so far.
A limit entity which could rewrite our definition of the living
The discovery of Sukunaarchaeum Mirabile upsets our understanding of minimum life. Indeed, it calls into question the distinctions established between biological autonomy and total parasitism. This unique case obliges biologists to rethink the fundamental criteria of life.
Beyond this cell, researchers think that it might only be The first in a series. There may be a whole ecosystem of similar entities, invisible so far, which evolve on the edge of the living.
Ultimately, this living enigma reminds us that nature is full of surprises. And above all, that even in the depths of plankton, it continues to push the borders of the possible.