This post reports a new form of life that is clearly a member of the archaea, with characteristics of that group, but also lacking a vital feature of other archaea as well as other bacteria and all eukaryotes: metabolism: the pathways (mostly involving enzymatic proteins) that keep an organism going and reproducing by converting nutrients into energy. Its lack of genes for metabolism makes it resemble a virus, what hijacks its nutrients from the cells it infects. But viruses can’t completely self-replicate like this new critter, for viruses also partly hijack the DNA/RNA replication system of their hosts.
The new creature, whose appearance is unknown since it was identified from DNA alone, must get its metabolites through association with other species. Finally, the new creature does have something that viruses lack—a complete system for replicating its genome: ribosomes, DNA, genes for transfer RNAs, and so on. In other words, in important ways it’s different from viruses, but also different from other archaea as well as bacteria and eukaryotes (organisms with “true cells” that have their DNA in the nucleus and have membrane-covered organelles like mitochondria and chloroplasts). The DNA of this creature is in a single circular chromosome like that of bacteria and archaea. Its unique features appears to make it a member of a new domain of life.
The question is this: is this new organism even alive? Viruses are regarded by many biologists as “not alive” because they can’t grow, they have no metabolism to sustain themselves, and are completely dependent for reproduction on the replication machinery of other organisms (bacteria or eukaryotes) they parasitize.
Well, read about this new organism below, discovered by sequencing DNA inside of a singe eukaryotic cell tell me if you think it’s “alive.”
But I’m getting ahead of myself. Let’s review:
There are three domains of life: the bacteria, the archaea (discovered only in 1977 by Woese and Fox), and the eukaryotes (everything else, all having membrane bound nuclei and organelles). Together, the bacteria and archaea are called “prokaryotes” (i.e., single celled microorganisms), and everything else besides viruses comprise the “eukaryotes.”
The phylogeny (family tree) of these domains is shown below. It was realized only recently that all organisms with true cells (e.g., us) descended from archaea, as shown below. That means three things. First, we are more closely related to the archaea (which often live in weird places like hot springs or hyper-salty water) than we are to bacteria. Eukaryotes did not evolve from bacteria.
Second, eukaryotes like us could be thought of as archaea, since we are nested within that group. In the same way, we could be thought of as fish, and birds as reptiles.
Finally, archaea are considered paraphyletic: the group does not contain all the descendants of its common ancestor. The eukaryotes are not considered archaea, but ARE descendants of the common ancestor of archaea; they just branched off later into a new domain of life.
Now this family tree was constucted from DNA sequence similarity, but archaea also share certain traits with eukaryotes that bacteria don’t have, including “shared metabolic pathways, similar enzymes involved in transcription and translation, and DNA replication mechanisms.” That is what a query to Google tells me. Remember, this area is far from my own biological expertise, so if you see an error, let me know!
This tree is from Sadava et al. 2020. Life. The science of biology. 12th edition. Oxford Univ. Press)
Here is a comparison of the traits of the groups (there are overlaps),from Wikipedia.
Note that all three groups have metabolism (pathways to produce energy and grow), and cell walls, but eukaryotes have a special cell wall with two layers of lipids and a layer of protein. Viruses, not shown in this comparison, have only a protein capsule around them. (Bacteria and archaea have more complicated cell walls.)
Viruses do not metabolize and are widely regarded as “nonliving particles”. Bacteria and most archaea have metabolism.
The paper describing the new finding is apparently not yet published, but you can find it at bioRχiv by clicking the title below or downlading the pdf here.
How did they find this thing? In a weird way. The researchers took a single individual of the dinoflagellate Citharistes regius and amplified and sequenced all the DNA it contained. Besides the DNA of the dinoflagellate, it also found DNA from three other types of organisms: cyanobacteria (photosynthetic bacteria once called “blue-green algae”), two species of gamma proteobacteria (a well-known group) and then the weird species under consideration, which they call Candidatus Sukunaarchaeum mirabile. This apparently means it’s a candidate species that hasn’t been formally described. We’ll call it CSM in this post. We don’t know what it looks like or what its ecology and behavior is, except we know it must be parasitic, commensal, or symbiotic with some other species. It cannot live on its own because it can’t metabolize.
Here is its genome shown in the paper. This is all we know of the organism’s biology:
It is in the Archaea as the DNA certainly shows its affinity. But, as shown below, its lineage originated very soon after the archaea branched off from their common ancestor with bacteria.
It has a very small genome: 238,000 base pairs, though that is not the smallest genome known of any organism in the three domains of life (note I’m using “life” here, though this thing may be more virus-like and hence “not alive”).
The chomosome is circular, presumably because sequencing it, one arrives back at the beginning again.
It has 222 genes, most of which are devoted to the machinery for making copies of itself. These include transfer RNAs and ribosomal RNAs, which are not found in viruses, all of which hijack that stuff from the cells they infect.
It has NO genes for metabolism (no genes for it), so CSM must grow and divide using resources from cells that it hijacks. Other bacteria and archaea (and of course eukaryotes) have the genes for metabolic processes, making CSM more virus-like. But, as I said, it differs from viruses by having a complete set of “self-replication core machinery” and genes that are like those in archaea.
189 of its 222 genes make proteins. All but five of these are devoted to self-replication. Several are very large and strongly suggest that they constitute part of the cell wall (they call it “membrane”), though the researchers are not sure about this.
Here’s a summary of the organism. Note that its unique character, lacking metabolism, makes it distinct from other domains of archaean life.
And a figure from the paper (just look at “a” on the left side) showing where it fits in the family tree of prokaryotes. It branches off from the rest of the archaea early, and then evolves very fast, as you can see by the long branch of its lineage, probably reflecting strong natural selection on the lineage.
To summarize:
CSM is an Archaea as seen from its DNA sequence. Of this there is no doubt.
But unlike other Archaea or even bacteria, it has NO metabolic machinery. In this way it’s similar to a virus.
But it is dissimilar to viruses because it has the complete machinery for self-replicating its genome, which viruses lack.
Ergo, it must be associated in some way with other organisms to be able to replicate.
We have no idea what it looks like, though it almost certainly is a cell rather than a virus.
Here’s how the authors highlight CSM’s uniqueness:
The discovery of Sukunaarchaeum not only expands the known boundaries of archaeal diversity but also challenges fundamental concepts of cellular life. The extreme metabolic simplification raises fundamental questions about the minimal requirements for cellular life. Sukunaarchaeum, focused almost entirely on genetic self-perpetuation, represents a compelling example of how far metabolic reduction can proceed within a cellular framework. Its minimal genome, absolute host dependence necessitated by profound metaboliceduction, rapid evolution, and significant investment in large, membrane-associated proteins potentially mediating host interaction constitute a unique combination of characteristics that are collectively reminiscent of viruses. Nonetheless, Sukunaarchaeum remains fundamentally cellular – a key distinction from viruses, which typically lack their own core replication machinery genes and rely on host systems. It possesses ribosomes and the core transcriptional and translational apparatus inherited from cellular ancestors. Thus, while clearly cellular, its extreme metabolic dependence and specialization for self-replication are virus-like in nature, suggesting that Sukunaarchaeum may represent the closest cellular entity discovered to date that approaches a viral strategy of existence.
The authors found this organism by sequencing a single eukaryotic cell; CSM was likely inside this cell, like a virus in a human cell, but we don’t know if CSM damages its host(s) in any way. It is likely that many more organisms like this exist but aren’t known because people don’t do DNA sequencing of entire single-celled eukaryotes very often. Dinoflagellates are aquatic organisms, but there may be more stuff like CSM found by sequencing DNA in the soil.
I’ll add that this organism might give us an idea of how viruses originated because, if it loses some of its core replication machinery and genes for making membranes, it would become a virus. It is unlikely to be a virus that might develop into an archaean, as it already is an archaean with a membrane, but would have to evolve a tremendous amount of new metabolic machinery to be able to fuel itself, and that metabolic machinery would have to be genetically similar to the metabolic machinery of already-existing archaea. That would be an unheard-of event of convergent evolution, thus very unlikely. This thing, so far, is sui generis.
Finally, IS IT ALIVE? That, as you might guess, depends on your definition of “life”.
If you count the ability to self-replicate on its own, CSM is alive. In that sense viruses are not alive, and most of us think they’re not. (Bur remember that it needs to be assocated with another species to self-replicate.)
But if you count the ability to sustain itself by metabolizing and fueling its own replication, then it is NOT alive.
You pays your money, you takes your choice.
This is amazing – thanks for this analysis!
I tend to think of viruses as pseudolife, alife, or fancy sort of nom de plumes like that… as in, saying something is not life implies there is some resemblance… vs. a rock being not alive in any way except for exhibiting a consciousness that Deepak or Philip Goff (panpsychism) gnostically know is true.
I knew you would have a Bryanoid take on this.
🎯
😁
–oid is good too – lifeoid…
Dawkins even applied it to… design – so, designoid… think that was in The Blind Watchmaker…
Wouldn’t get past peer review though…
The discovery as described seems too important to be based only on a genome sequence. Without micrographs of CSM cells themselves, or observations of their growth in (or out of) the host cells, or some other biology, I’m skeptical that this is just some kind of weird artifact from DNA contamination plus the assembly algorithm that turns the sequence data into a genome assembly.
Well, we shall see! It may be a one-off since it may be one of many weird things and detected only once. And of course it’s not accepted for publication yet. But I though I’d publicize it.
Is it possible that it actually is just DNA and the products encoded therein which don’t participate its own replication only contribute to to the phenotype of the host?. I.e., it appears as if it could exist without any own cellular structures and it may be impossible to take any such pictures. It should be still possible to stain its genome in situ, though.
I’m just a layperson who’s interested in microbiology, but this was my reaction, too. Extraordinary claims require extraordinary evidence.
This is great! Some deep evolutionary science to ponder. For me, in haste, with things to do today, I will savor this later. There are some deep thinkers associated with OSU (e.g. Eugene Koonan & co-publishers, check it out) who have written extensively about the evolution of viruses. Current thinking is that viruses co-evolved with the earliest cellular life. “Alive” or not, viruses and virus-like genetic elements have always been inextricably intertwined with cellular life.
Edit — mine written before Mike Hart, above. My first response is that he’s raises a central point, that it’s so important we’d like to see a lot more, and micrographs would be helpful. other correlative data. The questions he raises are important, so here’s to a careful reading of the paper. I wonder what the reviewers would say.
Thanks for bringing this to us, Jerry. I had heard about this but like so many things one hears these days, it is hard to separate wheat from chaff…I rely on some trusted resources like WEIT and its readers/commenters to best understand what is real. After my 2009 retirement as an aerospace engineer, whose only previous course in biology was in high school in 1964…when fungi were plants… I decided to try to catch up by reading. Great videos and books such as Dawkins’ “The Ancestor’s Tale” and Nick Lane’s “The Vital Question” and of course, your “Why Evolution is True” along with the easy access on the web to Worse’s papers has been extremely helpful. I even audited a freshman college biochem course, called “From Atoms to Cells” (it was really from molecules to cells but still really great!). I expect to be busy (and happy) with trying to understand this post and ensuing comments for several days. Thank you!
“… high school in 1964…when fungi were plants… ”
LOL 😆
When I did my A-level and S-level in Biology (1976) I believe the classification was limited to two kingdoms! Now it looks like we may need another domain. Fascinating stuff, Jerry. If confirmed, it throws light on the development of complex life, no?
Don’t forget Protists!
An interesting question. It seems to me it really just comes down to the words we use to describe things, which can be slippery or anyway, contextual. Is it alive? Depends on your definition of life. Is Pluto a planet? Depends on your definition of planet.
To me, they are not alive. With abject apologies to Stephen Colbert; they have “alivieness”; something that looks alive, if you squint hard and ignore a few things. Just as most pronouncements from the White House have an air of truth to them, in reality they are mere truthiness; these things have the appearance of being alive, but they’re faking it too. IMO,OC
It is necessarily the case that the category “living” is fuzzy edged, such that some organisms have some of the characteristics of being “alive” but not all. If this were not the case, and there was a clear-cut divide, then abiogenesis would not be possible and we wouldn’t be here to ponder the issue.
Exactly, if life is the result of an evolutionary(-like) process from non-living matter, we should expect to see some gradience.
We do seem to have some clear-cut distinctions between “living” and “dead” individuals, and between “living” and “extinct” species.
And “alive” is clearly a social construct, oppressively imposed by the elite objects that self-identify as “alive”. (Surely I don’t need a ‘/s’ on this, do I?)
Speaking of Pluto, I find Neil deGrasse Tyson infuriating obtuse when he speaks of sex and gender. His attitude seems to be that careful, logical definitions are needed when we discuss important scientific questions such as how best to think about icy dirtballs that orbit the sun. But biological sex is whatever and who cares.
There’s a meme with the heat map from the paper that reported brain MRIs for “liberal” v. “conservative” test subjects – maybe you’ve seen it …
I think it is accurate to your comment – much concern/brain activity for “all natural things in the universe including inert entities such as rocks”
I pause there…
This figure:
https://www.nature.com/articles/s41467-019-12227-0/figures/5
… reminds me of the notion :
if everything matters, then nothing matters…
Oy. Why are some things always worse than I imagine they could be?
Seems to be a new organelle derived from an intracellularly symbiotic archaeon. These symbionts typically loose metabolic genes to the host genome (genome reduction) but retain the ability to reproduce themselves like mitochondria and chloroplasts.
Unlikely because dinoflagellates have been studied extensively, yet nobody has reported an organelle different from the regular ones. Of course we should study them more, especially this species.
I should point out that there are tons of studies finding organisms, both archaea and bacteria, that are known only from their DNA: the so-called “ghost lineages”. I’ll try to post something about them soon.
These things remind me of the prokaryotes chlamydiae, which also have reduced genomes (1000 – 1300 kbase pairs acc. to Wikipedia) and, lacking ATP synthesizing machinery, are also obligate intracellular parasites. Like other bacteria they are membrane-bound with the usual circular chromosome but no membrane-bound nucleus or cytoplasmic organelles. They do have typical bacterial ribosomes and synthesize their own proteins, with which they can synthesize whatever else their genes code for. They just need host-cellular ATP to drive it all. Like viruses, they have a non-metabolizing spore-like form that allows the chlamydia to survive without inactivation in the environment until it finds a new host cell, which it enters and begins to proliferate, temporarily losing its ability to infect a new cell. The process resembles, but only in the most superficial sense the virus replication cycle. Nonetheless most microbiologists have little difficulty regarding chlamydia as a life form, “alive” at both stages.
CSM appears not to have any metabolic machinery at all but it does have its own ribosomes (or at least the genes to code for them) on which they would synthesize their own DNA and RNA polymerases if I have it right. So they are not completely incompetent for metabolism because protein synthesis is metabolism. It would seem they would need host catabolic enzyme systems not only to make ATP to drive everything but also the other precursor molecules for synthesis of nuclei acids, carbohydrate polymers, and lipids. Can they make adenosine from adenine and ribose, for example, or do they need preformed host adenosine to incorporate into nucleic acid polymers? (Ditto for T/U, C, and G. I just exemplified with adenine because it turns up in so many other places in metabolism, too.)
I’ll remain open-minded as to whether CSM can be called alive. I’m just impressed with the degree to which a set of genes can be stripped down and still maintain itself as an independently replicating and evolving entity. Membranes rock! Thanks for bringing this discovery to our attention.
I have various issues about the gravity of this discovery, although it is very interesting.
I wanted to first bring up that the origins of Eukaryotes had been complexified a while back. I am a bit confused on the latest take on things, but I’ve understood that since the 3-domain hypothesis, a later consensus emerged where Eukaryotes owe their origin to a fusion between an Archaean cell and a Eubacterial cell. This is called the Ring of Life Hypothesis (or Theory, to some).
The early discovery of the Archaean domain and their similarity to Eukaryotes was based on comparisons of rRNA. All well and good back in the day when genome comparisons was a laborious process. But more comprehensive studies since showed that the Eukarya have a hybrid genome, where some genes show stronger relationships with Archaea, while other genes show a stronger relationship with Eubacteria. A relevant spin-off of this fusion event is that mitochondria are a direct descendant from the Eubacterial cell that did the fusing.
Here are some references, although chunks of this go over my head:
https://royalsocietypublishing.org/doi/10.1098/rstb.2014.0323. And…
https://www.researchgate.net/figure/The-ring-of-life-hypothesis-Schematic-representation-of-the-flow-of-genetic-material_fig1_262230200 (you can navigate to the full article).
I vote “Alive”. My criterion for being alive is that any entity that can evolve adaptations in response to its environment by natural selection counts as living. Hence, even viruses are living entities. Maybe even prions.
I suppose it’s the difference between ‘Alive’ (an active actor; requires energy and therefore a metabolism) and ‘Life’ (everything that fits into phylogenetic lineages).
(Some) viruses’ heritage as either genome-reduced, specialised parasites that used to be bacteria, or rogue genetic code of more complex organisms also going down the parasite route makes it clear that non-metabolic organisms are unquestionably ‘Life’. They’re genetic replicators. Case closed.
But they’re also passive replicators. They do not react to outside stimuli. To be meaningfully (re)active replicators, they’d need energy, and to get energy, a metabolism. Hence, not alive.
I used to be firmly in the ‘Alive’ camp until I realised that ‘Life’ and ‘Alive’ aren’t synonymous.
It’s kind of the reverse of a hypothetical AI in the science fiction sense. The AI would be alive, but not life. The virus is life, but not alive.
And our reduced archaean is… who knows. Maybe alive when it can leech energy off a host, but not alive when not inside a host?
When a virus invades a cell and takes over the cell’s metabolism for its ends, that metabolism is now viral. The viruses that are eventually made and released are like sperm cells looking for another cell to invade. So I guess viruses (and sperm – which have viral genes that have been horizontally transmitted for fusion into the cell’s membrane) could be said to alternate between being alive and being life.
Vincent Racanielo takes the view that a virion is not alive, but once it invades a cell it springs to life.
That’s reasonable. Well, I wouldn’t go so far as to call sperm cells not alive unless they invade a cell, they are active organisms outside of it, too. But reasonable for the virus side.
If obligate parasites are “alive” then this should be too.
I define life as hereditary. Anything that can have changes to its hereditary content, and those changes are passed on to future generations and then is subject to natural selection is life. Very simplistic I know, but as a physicist, it works for me.
I like that definition Mike. I’m very curious about these things.
I audited medical school at uni and didn’t proceed with it but I’ve been reading about biology all my adult life. Still a rank amateur though!
D.A.
NYC
Thanks Jerry, very cool, and yet another topic to add to my Intro Bio class. Whether or not these are alive or the paper gets through peer review, it shows that science is always dynamic, ever changing, ever challenging us. That’s the most important concept one could bring to students.
I don’t know much about viruses, but is it possible this shows a way for viruses to have evolved? Could it be that a prokaryotic cell kept reducing its genome until what was left was what we call a virus, and this new discovery is simply an intermediate step?
There are two big questions here. Does CSM represent a new domain in the tree of life? Is CSM alive?
Is there a consensus about what is a domain? CSM emerges from within the Archaea, with a greater affinity to a group called the Nanobdellati. I am suspicious that declaring a new domain out of this looks like aggrandizement, but I don’t know how this will settle since I don’t know if there is a clear definition about what is or is not a domain in the tree of life.
Is CSM alive? I find it interesting that we live in a world where the distinction between life and non-life is blurred. There are many life-like things around us, but they are not considered (quite) alive. Fire and growing crystals assimilate materials and environmental energy to self-organize and grow and have a kind of homeostasis. So they have “metabolism” in a very loose sense. But fire and crystals lack a “replicator” for storing information, and they lack other things that are always associated with life. Viruses have the replicator, they are organized, and they evolve as populations (which is another thing that life has, or so we say), but they lack any whiff of metabolism. So it is broadly viewed that none of these things are alive although they are life-like. Life has to check certain boxes, and things that don’t check these boxes are not alive.
CSM lacks metabolism on its own, so I think we are pretty much done here. CSM is not alive, imo, although it does expand out the blur between life and non-life a bit more and it looks like it has been derived from living cells.
So interesting!
The authors say that the new life-ish form branched off from the Archaea soon after the Archaea themselves appeared. Could it be that the new life-ish form lost its metabolic machinery secondarily? Since the Archaea have metabolic machinery, if the new life-ish form is derived from the Archaea, it would seem to have lost its metabolic machinery when it took up its new lifestyle as a parasite-ish thing.
Secondary loss could explain the similarity to bacteria. Otherwise, one would have to postulate that Archaea without metabolic machinery evolved first—at which point the new life-ish form branched off—and that the Archaea then gained metabolic machinery later, with earlier evolved Archaea (not having metabolic machinery) having all gone extinct but for this one life-ish form. I am no expert on these enigmatic entities that lie at the root of the clade of life, so can easily be completely off base. But loss of metabolic machinery seems more parsimonious at first glance. Just trying to be a good cladist here.
Is it alive? That seems to be a matter of definition. Provide me with a definition of life and I will provide you an answer. (I’m being a bit dramatic in making this statement.)
Obligate parasites cannot live w/o their host(s), by definition, but no one claims they are not alive. Of the many definitions of live, the most common theme seems to be Organic Evolution. So, if these buggers evolve by descent w modification, they are alive. That’s my 2 cents.
Obligate cellular parasites cannot live independently of their hosts, but they do carry on various metabolic pathways within their cells and so they still check those boxes for being alive. True, they can lose some of those pathways. There are parasitic Eukaryote protists that lack mitochondria, and so they only do limited amounts of cellular respiration on their own. But they do have other metabolism.
“…but eukaryotes have a special cell wall with two layers of lipids and a layer of protein.”
I believe that you’re referring to the cell membrane here – a phospholipid bilayer with proteins salted through it.
As the Wikipedia table indicates, eukaryote cell walls vary in composition among groups – there’s chitin in fungal cell walls, for instance, and plant cell walls are primarily composed of cellulose. And some eukaryotes, like us, don’t have a cell wall at all, just a naked cell membrane.
Another great science posting – please keep these up, we read them and learn from them.
Thanks for doing this Jerry, looks very interesting. I don’t have a strong feeling about whether these guys are alive, but I do have a question regarding lineage. If eucaryotes are archaea with internalized bacteria the question of which line we are closer to seems a bit like asking if we are more related to our skin or our liver. Would the last common ancestor be archaea, bacteria or the combination? (Not quite on topic but there is also the question of which organelles came first – I assume that mitochondria and chloroplasts represent separate or possibly sequential bug-napping events?)
Earlier this week I listened to Karen Lloyd (USC) talking, among other things, about archaea from inside the earth that contain the machinery to encompass and maintain bacteria but have not done so – presumably representing a lineage close to that that gave rise to eukaryotes (Mindscape episode 314). The question of what this machinery is for is still, apparently, open.
Looking forward to reading when I have some time. Science posts can take me a bit of time.
Thank you for the post.
I think you can find this article very interesting:
Eukarya the chimera: eukaryotes, a secondary innovation of the two domains of life? Trends in Microbiology, 2022. https://doi.org/10.1016/j.tim.2021.11.003
The article you mentioned you used for the comparative table (Information Processing Differences Between Archaea and Eukaraya—Implications for Homologs and the Myth of Eukaryogenesis), is from a journal related to the creationist movement, thus, their arguments are not backed up within the scientific community.
Seems like such an organism would need an awful lot of transmembrane transporters for more complex metabolites and macromolecules that other cells wouldn’t have evolved. Maybe it has larger less specific pores in its membrane like nuclear pores or mitochondrial porins?
Fascinating. Thank you for this detailed post. Our world is immense and amazing.
More amazing developments in the history of life .
https://www.abc.net.au/news/science/2025-05-15/fossil-footprints-early-animal-ancestors-discovered-victoria/105275336
“Amateur palaeontologists have found the earliest-known footprints of a reptile-like creature called an amniote.
The tracks are about 356 million years old, pushing back the origin of reptiles and other land-based creatures by 40 million years. ”
Abstract published in Nature
In the context of the origins of life, when non-life became life, one definition is that life began when molecules of information (which could have been RNA) started to reproduce and evolve by natural selection. This implies that very simple forms (much simpler than LUCA) can be considered alive, so long as they have phenotypic variation and hereditary material. I like this definition. Based on it, I’d say that both viruses and CSM are alive.
I’m really not interested in this living or non-living discussion. I’m a virologist and don’t regard the question of “are viruses alive or not” as important. Viruses do what they evolved to do as do all other organisms. What is most likely is that viruses and other replicating things came about through abiogenesis and diverged very early on considering viruses have many different types of genome (double stranded and single stranded DNA, positive and negative single stranded RNA and double stranded RNA, the latter being the subject of my DPhil many years ago).
I wonder what would have happened if Wolbachia pipientis DNA had been identified within the Drosophila ananassae genome before Wolbachia had been identified as a bacterium. Would this have been discussed in terms of living or not living?
Comment by Greg Mayer
I’m an evolutionary biologist, with no special knowledge of microbiology. Four immediate thoughts. First, I don’t know how they know this is an intact organism within the host. Overlapping reads of sequence that link up to form the 238K bp? I suppose that would work. Second, it is reminiscent of the endosymbionts (mitochondria, chloroplasts) in eukaryotes, that started out as “whole” organisms, but have lost large parts of their genomes as they became more tightly integrated with their hosts. (This was noted above by Timothy D Swain.) Third, viruses evolve by natural selection and are obviously alive. I’m surprised that the contrary thought persists. (It would imply that it is possible for living beings to evolve to be dead.) Fourth, I don’t know the rules of bacterial nomenclature, but in zoology someone could (and there are those who would) “steal” the discovery and publish a name and diagnosis of the creature, thus becoming the official describers of the taxon.
GCM
Did we just find the missing link? Or perhaps I misunderstood most of it…
I read that archaea evolved from bacteria. Is it now an established scientific fact that both evolved from a common ancestor?
Yep.
Thank you and keep the science posts coming! Awaiting the confirmation by other researchers, and of course the furious searching for more if true.
Absolutely fascinating discovery. Shows how complex and completely absorbing biology can be.
According to Richard Dawkins life began with the appearance of the first self-replicating molecule, and I think it would be wise to stick with that definition. This makes sense because, arguably, that was when evolution by natural selection would have started. This rules out viruses as being alive because they cannot self replicate: they need to get into a cell (either eukaryotic or, in the case of bacteriophages, prokaryotic cells) in order to hijack the cells reproductive systems so they can get their genes into the next generation.
If, instead, we go with the first cells, with all their clever jazzy metabolism and reproductive complexity, as being the beginning of life it opens the door wide open for creationists to say that these are simply too complex to have originated in one step – actually one of the few things they say that’s true.
The question of what is alive and what is not alive, what is conscious and what isn’t, what is human and what’s not are all parts of the same old problem: evolutionary gradualism. One evolutionary “kind” inches into another by degree and poor old biologists and philosophers are left with the problem of satisfying our human inclination to apply names and categorise things out of the greyness of gradual change.