A cell so minimal that it challenges definitions of life
quantamagazine.org
quantamagazine.org
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
The new one with 238 kbp:
> Sukunaarchaeum encodes the barest minimum of proteins for its own replication, and that’s about all. Most strangely, its genome is missing any hints of the genes required to process and build molecules, outside of those needed to reproduce.
Referencing the 159 kbp one:
> However, these and other super-small bacteria have metabolic genes to produce nutrients, such as amino acids and vitamins, for their hosts. Instead, their genome has cast off much of their ability to reproduce on their own.
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?
The actual paper states that the genome encodes transfer RNA's and ribosomal RNA's. I think that's a really important biological distinction missing from the popular press junket. The primary source material is well written and elucidates a lot more than the Quanta article. https://www.biorxiv.org/content/10.1101/2025.05.02.651781v1
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.
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).
Inevitability of Genetic Parasites Open Access Jaime Iranzo, Pere Puigbò, Alexander E. Lobkovsky, Yuri I. Wolf, Eugene V. Koonin https://academic.oup.com/gbe/article/8/9/2856/2236450
> ... 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.
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.
If you say "well not by themselves" neither do humans.
There is another life property that this object does not fulfill and is called Teleonomia, that is governed by an ultimate goal.
I have bad news for you. Again, it's humans.
They are infectious agents, but many life forms are infectious agents.
<https://en.wikipedia.org/wiki/Organism>
Which specifically addresses edge cases including viruses, which "are not typically considered to be organisms, because they are incapable of autonomous reproduction, growth, metabolism, or homeostasis".
<https://en.wikipedia.org/wiki/Organism#Viruses>
Specifically, viruses have no innate metabolism, or energy-producing chemical reactions.
<https://en.wikipedia.org/wiki/Metabolism>
The terms "live" and "killed" have historical origins, but would better be read as "active" or "deactivated", and the immediately succeeding sentence clarifies this: "Live vaccines contain weakened forms of the virus, but these vaccines can be dangerous when given to people with weak immunity."
For more on the distinction see: <https://www.biologynotes.in/2024/03/difference-between-live-...>.
And yes, there are infectious agents which also happen to be organisms, such as bacteria, amoebas, funguses, etc. Tuberculosis (Mycobacterium tuberculosis), many stomach ulcers (Helicobacter pylori), botulism (Clostridium botulinum), and e. coli poisoning (Escherichia coli) are all infectious disease caused by bacteria. Giardiasis is a G-I infection of the Giardia amoeba. There are numerous fungal infections (many UTI infections, athlete's foot, jock itch, nail infections).
Further down the non-life infectious agent chain are prion diseases such as Transmissible spongiform encephalopathy ("mad cow" disease in cattle, "Creutzfeldt–Jakob disease", amongst others). These are literally misfolded proteins, which lack not only metabolism but any genetic material (DNA, RNA), but still propagate.
More on infectious agents, a/k/a pathogens: <https://en.wikipedia.org/wiki/Pathogen>.
> That article (and the more general article on viruses) both pointedly avoid referring to viruses as organisms
As if you expect people to carefully read the whole article, notice it doesn't mention anywhere whether viruses are alive, and conclude that by not mentioning this it supports your claim. By the same logic, it pointedly avoids saying viruses aren't alive.
The main article on viruses has a section that addresses directly whether viruses are alive (https://en.wikipedia.org/wiki/Virus#Life_properties):
> Scientific opinions differ on whether viruses are a form of life or organic structures that interact with living organisms. They have been described as "organisms at the edge of life", since they resemble organisms in that they possess genes, evolve by natural selection, and reproduce by creating multiple copies of themselves through self-assembly. Although they have genes, they do not have a cellular structure, which is often seen as the basic unit of life. Viruses do not have their own metabolism and require a host cell to make new products. They therefore cannot naturally reproduce outside a host cell—although some bacteria such as rickettsia and chlamydia are considered living organisms despite the same limitation. Accepted forms of life use cell division to reproduce, whereas viruses spontaneously assemble within cells. They differ from autonomous growth of crystals as they inherit genetic mutations while being subject to natural selection. Virus self-assembly within host cells has implications for the study of the origin of life, as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules. The virocell model first proposed by Patrick Forterre considers the infected cell to be the "living form" of viruses and that virus particles (virions) are analogous to spores. Although the living versus non-living debate continues, the virocell model has gained some acceptance.
One of the few places I've seen it come up in science, was ecosystem multi-scale simulation software. Where virus was squarely in the heritable characteristics under selection pressure ("life") bucket, rather than abiotic or biogenic.
Informal "do you think of viruses as alive?" seems to vary by field. I've seen a marine bio labs be overwhelmingly yes. I've been told medical immunology leans no. But it seems more social-media engagement question than research question or synthesis.
This is a decidedly Eukaryote-centric take. Homeostasis in higher mammals is a complex network of genes -> RNA -> proteins -> metabolic pathways
Reproduction is also far more simple in organisms with binary fission cellular division.
A more appropriate scientific term would be obligate commensalism vs. "parasitic". That actually encapsulates their need for metabolic precursors from the host, but allows for tRNA, rRNA, origin of replication, etc...present in the organism's genome.
Wikipedia on the definition of life:
> Since there is no consensus for a definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment. This implies all or most of the following traits: [list of seven common traits of life]
Last time I checked, they are considered "not alive" when outside of a host, and "alive" when inside a host.
About size: "Genome size varies greatly between species. The smallest—the ssDNA circoviruses, family Circoviridae—code for only two proteins and have a genome size of only two kilobases;[61] the largest—the pandoraviruses—have genome sizes of around two megabases which code for about 2500 proteins"
Yet people get hung up about it as if it’s a philosophical problem. It is not a philosophy problem. The word is loaded and you’re simply spending an inordinate amount of time trying to define some made up boundary of what fits this category you made up. It is a communication problem disguised as deeper.
Bacteria, fungus and plants are not usually seen as conscious but are usually seen as alive.
All conscious things are alive (unless AI is conscious) but not all alive things are conscious.
I suggest
If it can reproduce and mutate heritably, it's alive.
I find the idea that viruses aren't alive ridiculous.
Machines fit this definition.
Fire fits this definition.
Truth is "life" is not a distinct category. We just think of life as complex life. A complex system that mines energy gradients to preserve and replicate its forms.
But there's no hard boundary. It's just in our head.
People always come up with people-centric definitions. They need to be updated based on what are the fundamental characteristic of something that is alive.
The current, more standard definition, seems to be based on metabolism. I disagree and argue for reproduction and evolution.
Crystals can "reproduce", but it's always the same (there can be errors, but they don't inherit), so they don't count.
And atoms don't reproduce, so I'm missing your point there.
You could say "they have no heritability", and not the way you expect, I guess, but they all inherit the same local laws of physics, and they may even impact those laws, thus forming a feedback loop, and clearly there are googols of them in clusters, same weight, same energy, same polarity, same properties, same states, much like you see with any other species in nature, in fact in far lesser numbers.
If robots are made in a factory, does this count as reproduction? If not, why not. Does a mother's womb not resemble a "baby factory". A baby does not create itself. Always something else creates you.
We have clusters of "common sense" about these things, and most of what I said immediately sounds stupid to "common sense". Yet common sense falls apart if you start thinking about it. But Internet is not EXACTLY conductive to "thinking about it". It's all about the hot takes and the current consensus. Then time passes, and that consensus seems truly unenlightened.
Is an infertile animal (which can't reproduce) dead? What about a nerve cell (which have differentiated too far to become a reproductive cell)? Or a red blood cell (which has no genome)?
From the other end, is a genetic algorithm alive? What about a manuscript? Manuscripts are copied (so they reproduce), and have frequent copying errors, which propagate.
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.
Also, as others have noted, your idea is not necessarily wild. Certainly, at the sub-cellular level, there is tremendous evidence that symbiosis played a part in creating "higher level" organisms (i.e., eukaryotes).
Many genomes are like a junk-yard with fossilized relics of infectious agent nucleic acid (e.g., viruses), etc. Apologies for the junk-yard / fossil mixed metaphor.
They aren’t. Apart from DNA replication, transcription, and translation, their genome lacks elements encoding for even the most simple metabolic pathways.
This scishow video gives a good look at the tip of the iceberg.
There are many levels of abstraction between quantum/particle physics and life, or even just cosmology (things like dark matter, etc), that we really know very little about.
Chemistry is adjacent to physics, at least classical physics and the standard model, so you might think that we should be able to use our knowledge of physics to determine things like atomic bond "angles" and the protein folding problem, yet even this smallish step up in abstraction from physics puts us in a realm where we know very little. DeepMind's AlphaFold, now able to correctly predict 90% of protein folding in agreement with experimental determination, is mostly based on learning from experimental data, as well as evolutionary consideration of proteins that co-evolved, etc.
It makes you wonder how useful the reductionist model really is in terms of understanding higher level dynamics. Maybe different levels of abstraction like physics, chemistry, etc, are really a lot more independent than is commonly thought.
> If you can’t understand the distinction I’m making then you do not have the imagination and creativity to create new understanding.
Perhaps you could explain your distinction instead of insulting people. It’s possible you have some interesting and insightful distinction but as of now you’ve not explained it nor given any examples of this “more abundant” life.
Water does not freeze itself. That is the distinction. But myself, as a living being, can turn water into ice. And I can create an organize materials inside of my own body.
I pointed out something interesting. The least thing you could do is actually look up to see if there’s any validity or research on what I’m talking about.
By more abundant life, I’m talking about how the definition of life we have is limited, but it’s ever expanding based on the papers of the original post. I’m talking about a greater expansion of our understanding of life that’s discussed in papers that deal with entropy and life.
For instance:
https://www.quantamagazine.org/a-new-thermodynamics-theory-o...
But this has been a topic of conversation since the early 1900s. It’s not like I’m saying anything new.
At least own it. Saying someone lacks imagination and creativity and now reading comprehension is absolutely insulting.
> I pointed out something interesting. The least thing you could do is actually look up to see if there’s any validity or research on what I’m talking about.
I can’t look up anything based on your vague comment. That’s why I asked what you mean.
> For instance:
Thanks. I’ll take a look at that article.
I said: "You’re reading comprehension is failing you right now." The "right now" part menas that I am not saying it does not exist, just that they are not understanding what is written.
Why is it an insult to say someone lacks creativity? It was objectively true to me and it is not an insult, just a truth. Like if someone has red hair. At worst it was my opinion.
You know what an insult is? To take what I said to think that I meant that water turning to ice was life.
You were asked to make a distinction, the opportunity to provide some specificity to your fundamentally flawed You came back with snarkiness and
Yes, intimately familiar with England's work. My physics PhD was in statistical mechanics + biophysics.
Perhaps you don't know how thermo works? Your definition at the very least should define the environment to even be worth consideration. As is, I can either take it face value. In which case it's wrong. Or I can try to get a refined definition out of you, giving you the benefit of the doubt you know what you're talking about. Your attitude and answers don't give me confidence.
This is physics. Define things. We can't read minds.
1. Living things locally decrease entropy but globally increase it.
2. Many other processes do the same. As chermi noted, a liquid solidifying has the same characteristic.
Yes, living things locally decrease entropy and that’s my point.
And maybe I should’ve been more clear for people who cannot grasp new understandings, anything that can decrease its own entropy is living.
I mean, do you think life has nothing to do with the organization matter into a lower entropy state?