Isn't replication the single most important act of metabolism for an organism? I am trying to reconcile their ""lost genes include those central to cell metabolism, meaning it can neither process nutrients nor grow on its own" with their "The organism’s “replicative core” — the genetic components needed to reproduce itself — remains, making up more than half of its genome".

Replication (making DNA, RNA, and proteins, and ultimately dividing) is a highly energy-intensive and material-intensive process. What appears to be lost by Sukunaarchaeum are the genes to build basic building blocks (amino acids, vitamins, nucleotides) from scratch. It cannot find a sugar molecule and break it down for energy (it can "neither process nutrients nor grow on its own"). Yet it can take pre-made energy and building blocks and assemble them into a new organism.

What is the exact line between the host's metabolic contribution and the archaeon's replicative assembly? How "finished" are the raw materials that the host provides, and how does the archaeon's extremely reduced genome still manage the subsequent steps of self-replication?

Very impressive! To be clear, this is not the smallest known bacterial genome; only the smallest known archaeal bacterial genome, at 238k base pairs.

In the article they mention C. ruddii, with a smaller 159k base pair genome.

But according to wikipedia, it seems N. deltocephalinicola, at 112k base pairs, may be the smallest known bacterial genome. https://en.wikipedia.org/wiki/Nasuia_deltocephalinicola

Talking about tiny cells and staring at a tube with liquid. Made me chuckle.

I’ve been thinking about a wild theory regarding the incredible biological complexity we see in mammals today.

What if our bodies (apart from the brain) are actually the result of an ancient aggregation of once-separate "organisms" that evolved to live symbiotically?

Over millions of years, their DNA might have fused and co-evolved into a single, unified genome. What began as cooperation between distinct life forms could have gradually become inseparable, giving rise to the intricate multicellular systems we now take for granted.

I think the genome might be mostly just the "config file". So the cell already contains most of the information and mechanisms needed for the organism. The genome is config flags and some more detailed settings that turn things on and off in the cell, at specific times in the life of the organism. From this point of view, the discussion about how many pairs/bytes of information are in the genome is misleading. Similar analogy: I can write a hello world program, which displays hello world on the screen. But the screen is 4k, the windows background is also visible, so the hardware and OS are 6-8 orders of magnitude more complex than the puny program, and the output is then much more complex than the puny program.

> the bacterium Carsonella ruddii, which lives as a symbiont within the guts of sap-feeding insects, has an even smaller genome than Sukunaarchaeum, at around 159,000 base pairs

159 000 base pairs is ~320 Kbit, or 40 KBytes. I wonder, if that is the minimum size of a cell firmware. Also, if the cell is that simple, can we study it exhaustively and completely? Like, decipher every base pair in DNA, and determine what it is responsible for. And make an interactive website for that.

From the paper: https://www.biorxiv.org/content/10.1101/2025.05.02.651781v1

> ... 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.

Life is the process of decreasing entropy. If they stick with that definition, they’d be fine. And they’d find out that life is even more abundant than they can imagine.

See also: “Microbe with bizarrely tiny genome may be evolving into a virus” – https://www.science.org/content/article/microbe-bizarrely-ti...

> According to the shocked researchers

What is this, some content creator run Biohacker Lab in some basement on Microflix premises?

Ominous voice: the tiny cell withdrew into the cracks of existence and saved it's entire code to be in the lines between, the Singular Point which was neither a fraction of space, nor a unit of time, hidden in the void of Chututululu's (33rd degree cousin of Cthulhu) dreams, written in the unspeakable language of the subtext of the book of neither life nor death, that nobody would decipher until the time was right AND GODZILLA GETS TO WALK THE EARTH AGAIN.

The ultimate form of outsourcing.

Reminds me of how the discovery of giant viruses - like truly huge viral particles - was immediately also followed by discovering "virophages" which parasitized them.

Which of course makes sense to some degree: if an adaptive strategy is successful enough, then parasitizing something which successfully implements it is going to be resource favorable (and likely, presumably by being a member of that species and just shedding components you don't need if you take them).

We don’t even fundamentally understand physics yet. Certainly there is much to life that we don’t understand.