That’s interesting. The main difference seems to be that those other tiny organisms only encode how to produce some metabolic products for the host but cannot reproduce independently, so they are quite close to being organelles. Instead, this new one pretty much only produces the proteins it needs to reproduce and nothing for the host.

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.

A nitpick: Although similar in some aspects, archaea are not bacteria; they are classified under their own phylogenetic domain.

Still far, far too complex to occur "randomly," which is fascinating. The odds of 112k bases arranging in any meaningful way by chance within a membrane are the kind of thing you wouldn't get if you ran a trillion trillion trillion universes.

There's many hypotheses, basically all different variations on "soup of organic compounds forming complex catalytic cycles that eventually result in the soup producing more similar soup, at which point it begins to be subject to differential selection." It's a reasonable idea but where did this happen, and do the conditions still exist? If we went to that place would it still be happening?

There's reason to believe the answer would be no because modern lifeforms would probably find this goo nutritious. So life may have chemically pulled up the ladder from itself once it formed.

This of course assumes no to more fanciful options: panspermia that pushes the origin back to the beginning of the cosmos and gives you more billions of years, creation by a God or some other kind of supernatural or extra-dimensional entity, etc.

You could argue the same way for a lot of parasite species, many of which are ridiculously more complex. Is a complex multicellular organism (an animal even) not alive because it needs to get some component needed for its reproduction from another species? If you get hung on such specific components, where do you draw the line?

I wonder if this minimal cell could be described instead as something between a bacteria and a virus. I am not a biologist, but IIRC viruses penetrate cells then hijack the cell's standard machinery to replicate itself, until the cell explodes; sort of like a DNA/RNA injection exploit.

Makes me wonder, do geneticist count epigenetic methylation as information to add to the genetic information set ?

This is the biological equivalent of sectorlisp.

For comparison, the smallest bacteria genome, nasuia deltocephalinicola, is 139 kbp.

> Life's two most fundamental properties are homeostasis and reproduction. > The loss of these two combined with its parasitic nature makes this cell a form on non-life.

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.

You're being rigid about your preferred definition of life, but for what purpose? What is gained by categorizing this as strictly non-living?

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]

how do biologist consider virus like replication then ? which is a two-part system, the virus + the host (and even, a dense population of hosts)

Lots of types of life give up on homeostasis along particular dimensions because the environment is doing it well enough. Viruses do reproduce.

If you say "well not by themselves" neither do humans.

They were shocked. It is shocking.

That's an interesting definition, but it does have some issues.

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.

Atoms and sub-atomic particles fit this definition.

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.

Which, BTW, is about the same researcher and microbial host/parasite pair. More info, so I'm not complaining.

Maybe devolving would be a better term if that's the case

It's called Symbiogenesis [0] and it's not at all a wild theory. But it's limited to cell components, not multiples organs fusing to create something as complex as a mammal.

[0] https://en.wikipedia.org/wiki/Symbiogenesis

Why do you say "apart from the brain"?

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.

This isn't a wild theory or a novel one. It's well-established that endogenous retroviruses alter DNA and are inherited. In addition to the primary genome being modified this way, all mitochondria are symbiotic organisms inside plant and animal cells, with their own DNA, and are vital to life. Same thing for chloroplasts in plants. And then there are gut bacteria, which are vital to life, symbiotic, and directly influence evolution and the genome.

https://en.wikipedia.org/wiki/Intragenomic_conflict

You should look into the origin of mitochondria.

I believe that we’re living in that situation now. I don’t think life can be divided into smaller organisms. That there is just one complex life that we failed to see based on our past prejudice.

Maybe this is a case of an inception of overlapping genes?

> They're still eating stuff from their host

They aren’t. Apart from DNA replication, transcription, and translation, their genome lacks elements encoding for even the most simple metabolic pathways.

Which makes C. Regius a very tiny CEO? :)

Indeed. Well deduced.

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

Unsurprisingly maybe, DPANN archaea can also host viruses: https://www.nature.com/articles/s41564-025-02149-7 (Paywalled, but there’s a preprint at https://www.biorxiv.org/content/10.1101/2025.02.15.638363v1)

This is not so much about the understanding of life as it is about the definition of life.

We understand enough physics to model all the possible interactions life might have on this planet. Unless this planet is having a really bad day.

Let SCOTUS have a look, they seem to know what life is without the benefit of any bothersome science.

The definition of life is also uninteresting. At its core it is just a vocabulary and classification issue. We humans invented the word life and we humans chose to make the word vague, confusing and differently defined among different people. An arbitrary vocabulary and definitional choice for a word “life” is not in actuality interesting to think about.

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.

This is one of those things that sounds profound, but only until you think about it. Depending on how you read this, it either excludes life entirely or includes all sorts of things that are not meaningfully alive.

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.

What? A liquid solidifying is life?