The Eukaryotic Nucleus May Derive from a Giant Virus

Guest post by John Tillman

I previously posted on recent research into the origin of mitochondria, one of the two traits distinguishing eukaryotes from prokaryotes (Domains Bacteria and Archaea). The other defining characteristic, the cell nucleus, gives eukaryotes their name. Mitochondria almost certainly derive from endosymbiosis of an alphaproteobacterium by an Asgard archaeon. Now more evidence has emerged favoring the hypothesis that the eukaryotic nucleus arose from viral infection of an archaeon.

This post reports on an unpaywalled paper in the journal Virus Research from November last year, offering support for this Viral Eukaryogenesis hypothesis.

Evidence supporting a viral origin of the eukaryotic nucleus

Abstract
The defining feature of the eukaryotic cell is the possession of a nucleus that uncouples transcription from translation. According to the updated Viral Eukaryogenesis (VE) hypothesis presented here, the eukaryotic nucleus descends from the viral factory of a DNA virus that infected the archaeal ancestor of the eukaryotes. The VE hypothesis implies that many unique features of the nucleus, including the mechanisms by which the eukaryotic nucleus uncouples transcription from translation, should be viral rather than cellular in origin. The modern eukaryotic nucleus uncouples transcription from translation using a complex process employing hundreds of eukaryotic specific genes acting in concert. This intricate process is primed by the eukaryote specific 7-methylguanylate (m7G) cap on eukaryotic mRNA that targets mRNA for splicing, nuclear export, and cytoplasmic translation. It is shown here that homologues of the eukaryotic m7G capping apparatus are present in viruses of the Mimiviridae yet are apparently absent from archaea generally, and specifically from Lokiarchaeota, a proposed archaeal relative of the eukaryotes. Phylogenetic analysis of the m7G capping apparatus shows that eukaryotic nuclei and Mimiviridae obtained this shared pathway from a common ancestral source that predated the origin of the Last Eukaryotic Common Ancestor (LECA). These results are consistent with the hypothesis that the eukaryotic nucleus and the Mimiviridae obtained these abilities from an ancient virus that could be considered the ‘First Eukaryotic Nuclear Ancestor’ (FENA).

Transcription means the formation of Messenger RNA (mRNA) from a DNA template, which in eukaryotes occurs in the nucleus. Translation means using this mRNA to build the protein for which it codes, with Transfer RNA (tRNA) carrying the needed amino acids to the polypeptide assembly site on a ribosome in the cellular cytoplasm.

Ribosomes consist of a larger and smaller wad of Ribosomal RNA (rRNA), decorated with proteins. They’re similar in size and composition to RNA viruses. Ribosomal RNA is tRNA.

If further confirmed, this hypothesis means that Domain Eukaryota is nested within archaeal Phylum Lokiarchaeota, and that we eukaryotes descend from the symbiogenesis of an archaeon, bacterium and a virus. There is growing support for according Family Mimiviridae, aka “Giant viruses”, the status of living organism, rather than mere “replicant” among the many sub-alive “Mobile Genetic Elements”. They are large, double-stranded DNA viruses.

The first member of the family, Genus Mimivirus, was identified in 2003. It had been discovered in 1992 infecting an amoeba, but was mistaken for a bacterium. Typical viruses are about 100 times smaller than normal bacteria, but giant viruses are similar to them in size.

In related news about friendly viruses, a study from a year ago: 

How the placenta evolved from an ancient virus

Of the about 180 recognized viral families, 26 contain human pathogens, of which 18 are RNA.

Classification of Human Viruses

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BallBounces
January 15, 2021 4:44 am

“about 100 times smaller” What would one time smaller mean?

Reply to  BallBounces
January 15, 2021 5:02 am

Yeah. Like, when a ball is “1000 times smaller”, the diameter is only ten times smaller. Confusing.

John Tillman
Reply to  paranoid goy
January 15, 2021 6:04 am

The simplest significant virus, which causes polio, is about 30 nm in diameter. A larger than average bacterium would measure 3 microns in diameter, but some are less than a tenth that size and others over three times wider.

Length varies with shape, of course. There is such great variation in both viruses and bacteria that precise comparison in general isn’t possible. Mean order of magnitude is about the best I can do.

Same applies to comparing eukaryotes with generally much smaller prokaryotes.

Stan Brown
Reply to  John Tillman
January 15, 2021 9:52 am

Then why not go by mass instead of volume or length?

Jackie Pratt
Reply to  Stan Brown
January 16, 2021 3:31 pm

because they are all the same thing; measurements. Jeez

John Tillman
Reply to  Stan Brown
January 19, 2021 9:45 am

Average masses and volumes of microbes aren’t very meaningful. There is enormous variety.

John Tillman
Reply to  BallBounces
January 15, 2021 5:48 am

That would be the same size.

mcswell
Reply to  BallBounces
January 15, 2021 6:31 am

Also, is this “smaller” by linear dimension or by volume? Volume goes by the cube of the linear dimension (provided the object is roughly globular).

John Tillman
Reply to  mcswell
January 15, 2021 8:08 am

By dimension. Both bacteria and viruses vary greatly in shape. Structure, too, especially viruses. Many have icosahedral capsids with appendages. Even those with envelopes, like WuWHO, aren’t always globular.

Reply to  BallBounces
January 15, 2021 11:22 am

Thank you. This perversion of language has become common among intelligent people over the last couple of decades. One one-hundredth the size please. Many times smaller? I want to punch the wall.

pls
Reply to  Charles Rotter
January 16, 2021 12:41 am

Part of the decay of language generally. In this context, one should never use size. Say “length” or “volume” or “area” as appropriate.

John Tillman
Reply to  pls
January 18, 2021 3:19 pm

Not really possible when comparing all bacteria with all viruses. Away too much variation. It’s just a rough comparison. Same problem applies to comparing bacteria with eukaryotic cells.

John Tillman
Reply to  pls
January 18, 2021 3:56 pm

Largest known virus: Mamavirus, capsid diameter 500 nm
Smallest known virus: Porcine circovirus, capsid diameter 17 nm
Largest known bacterium: Thiomargarita namibiensis, 100 to 750 μm
Smallest known bacterium:Mycoplasma gentilium, 200-300 nm.

Smaller bacteria almost certainly exist.

So on average, two orders of magnitude is right, but exceptions exist with same to one order of magnitude in diameter, which might not be the right dimension for comparison.

I saved readers from at least a paragraph discussing these ranges. Point is, viruses are at least as much smaller than bacteria, as they are compared to eukaryotic cells. On gross average.

Antonio Moretti
Reply to  John Tillman
January 18, 2021 8:14 pm

Actually Tupanvirus ‘strains’ (though still in the virus ‘family’ of Mimiviridae) might be considered the ‘largest’ known viruses with optically visible tailed forms that can reach lengths of up to 2.3 μm and comprise some 1.5 million base pairs of DNA, with enough protein-coding genes to produce up to 1,425 kinds of proteins.

On the issue of dimensions, most microbiologists would consider ‘size’ to imply length/width and not volume or mass as it’s easier to envisage and measure length/width than volume (due to the huge diversity in microbial shapes) and mass (due to the impossibility to relate to that metric in everyday human terms for such minute entities). Of course, any scientist would appreciate that all of length, width, volume and mass, amongst other characterises, have value when looking at the way microbial cells work.

Oh, and by the way don’t forget about viroids that are the smallest infectious (plant) pathogens known. They’re composed solely of a short strand of circular, single-stranded RNA that has no protein coat. Interestingly, they’re the only known autonomously replicating pathogenic agents that do not encode proteins. Dimensions for these have to be in terms of nucleobases that range from 246 to 467 nucleobases in the 30 odd types discovered.

Last edited 1 month ago by Antonio Moretti
John Tillman
Reply to  Antonio Moretti
January 19, 2021 9:46 am

Thanks!
.
I mention viroids below

John Tillman
Reply to  Charles Rotter
January 18, 2021 3:18 pm

I wouldn’t go so far as “perversion”, but agree it would have been better to say that bacteria are typically on the order of 100 times larger than viruses, and to specify in what dimension or by volume or mass. But given the broad range of these measurements, simple order of magnitude gives an idea.

However, in English, “times” in arithmetic means multiplication. “Bigger” signifies that the multiplicand lies above the fraction line, while “smaller” that it’s below. Thus, “100 times smaller” means using “1/100” as a multiplicand.

For example, the number 100 times smaller than 1000 is ten (math notation 1000/100 = 10).

John Tillman
Reply to  Charles Rotter
January 19, 2021 3:30 pm

Thanks for editing and great art work.

January 15, 2021 4:58 am

I first learned the word “eukaryote” when I researched the intricate shapes of certain bacteria. When Darwin went on his little world cruise, he came back with a New Theory on Evolution. What (nearly) nobody knows, is that he was but one of many scientists on the …Beagle, was it? Anyway, another guy, Heackel, found the most intricate water-borne bacteria, and he made sketches of their “glass” shells.
With modern tech, we can actually take photos of live ones, to see how “tendrils” flow from each small hole, while dead empty shells refract light in rainbow colours, because of the (water solluble) glass shell.
Researhing pictures of glass bacteria shells was one of the most enjoyable uses for the internet I have ever found! I even built a presentation for some churchy friends, introduced them to this beauty by calling it “God’s Glass Sculptures” or somesuch.

Haeckel_Spyroidea.jpg
John Tillman
Reply to  paranoid goy
January 15, 2021 6:19 am

Those are radiolarians, ie eukaryotes, not bacteria. Ernst Haeckel photographed and named protists, ie unicellular eukaryotes.

Protista is not however a valid clade, ie natural group. It includes both protozoa and organisms closer to plants, such as algae.

mcswell
Reply to  John Tillman
January 15, 2021 6:32 am

But not including blue-green algae, right? Which are prokaryotes, and therefore more closely related to bacteria (IIRC).

John Tillman
Reply to  mcswell
January 15, 2021 8:10 am

Blue-green algae aren’t really algae but cyanobacteria, which are indeed bacteria, hence prokaryotes. Cyanobacteria is the correct term.

John Tillman
Reply to  paranoid goy
January 15, 2021 7:05 am

Beagle started out with two ship’s surgeons, McCormick and Bynoe. McCormick felt slighted by Captain FitzRoy, and left the ship in Brazil. Bynoe was of great assistance to Darwin, including caring for him while ill in Chile.

Darwin considered McCormick an ass. He had monitored lectures on natural history in Scotland, but Darwin found his ideas on geology outdated. On one stop, FitzRoy kept him aboard ship while Darwin went collecting ashore. Then the skipper sent Darwin’s collection back to Britain, but not McCormick’s, so he departed himself.

Besides these two surgeons, there were no other naturalists on Beagle.

otsar
Reply to  John Tillman
January 15, 2021 12:49 pm

It is hypothesized that Darwin was infected with Chaga’s disease in Chile. The chronic disease destroyed his nervous system later in life.

Joel O'Bryan
Reply to  otsar
January 15, 2021 8:02 pm

Lead poisoning and mercury poisoning are neurotoxic and were also common then from using lead utensils and drinking cups to using mercury as a fixative agent (as hatters used to do for pelts to make hats, i.e mad as a hatter because of neurotoxic mercury poisoning.)

John Tillman
Reply to  otsar
January 18, 2021 3:01 pm

He was bitten by a “Kissing Bug” in Argentina, but his sickness in Chile might have been a delayed reaction to infection with Chaga’s there.

rbabcock
January 15, 2021 5:29 am

from endosymbiosis of an alphaproteobacterium by an Asgard archaeon. “

.. words only a microbiologist would love

John Tillman
Reply to  rbabcock
January 18, 2021 3:21 pm

Not a microbiologist here, but I like being as specific as possible. However it appears I failed to offer enough specificity in comparing the scale of all bacteria with all viruses.

Mark Pawelek
January 15, 2021 6:08 am

We’re not even sure where viruses came from. There are 3 distinct popular hypotheses. I’m told viruses arose 1.5 billion years ago and eukaryotes emerged about 2.1 – 1.6 billion years ago. Yet viruses caused eukaryotes? There are also many variants of viruses, dsDNA, ssDNA, dsRNA, ssRNA. Some ssRNA viruses are positive sense which do not require mRNA to make proteins.

ss = single stranded, ds = double stranded

mcswell
Reply to  Mark Pawelek
January 15, 2021 6:33 am

I’m told viruses arose 1.5 billion years ago”: How would anyone know? They obviously leave no fossils.

John Tillman
Reply to  mcswell
January 15, 2021 8:20 am

When related viruses diverged from a common ancestor can be estimated by molecular clocks, but for that long a period, the estimate would be very imprecise.

mcswell
Reply to  John Tillman
January 15, 2021 10:24 am

Right–I thought about that, but I would think that the molecular “clocks” in viruses might run at quite a different speed than those in prokaryotes, which in turn might be quite different from eukaryotes–because how the three groups use DNA (or RNA, ico many viruses) is quite different. In other words, I would be skeptical of trying to calibrate virus “clocks” using data from eukaryote “clocks”. So as you say, very imprecise.

John Tillman
Reply to  mcswell
January 15, 2021 11:41 am

Viral molecular clocks are calibrated by the mutation rate in various viral lineages, not from mutations in cellular organisms.

John Tillman
Reply to  Mark Pawelek
January 15, 2021 8:18 am

Viruses may have preceded cells. They’re a lot older than 1.5 billion years.

DNA viruses might be degenerate cells, but all RNA viruses seem to descend from a common ancestor. Double-stranded RNA viruses however have evolved in separate lineages.

Positive sense RNA virus genomes are in effect mRNA.

Antonio Moretti
Reply to  John Tillman
January 18, 2021 8:21 pm

Positive sense RNA virus genomes are in effect mRNA.’

As, topically, in Coronaviruses.

John Tillman
Reply to  Antonio Moretti
January 19, 2021 9:49 am

yup, despite a fairly complex, enveloped structure, their function is simple, not requiring reverse transcriptase. Also, unlike flu viruses, their genome is in a single strand, not split up.

bonbon
Reply to  Mark Pawelek
January 15, 2021 8:38 am

I came across this, packed with images and detail :
Viruses as new agents of organomineralization in the geological record
https://www.nature.com/articles/ncomms5298

As regards ” The first member of the family, Genus Mimivirus, was identified in 2003. It had been discovered in 1992 infecting an amoeba, but was mistaken for a bacterium. Typical viruses are about 100 times smaller than normal bacteria, but giant viruses are similar to them in size.”

Just curious, but HIV infection seems to involve some kind of opportunistic small bacteria – could they actually be a giant virus?

John Tillman
Reply to  bonbon
January 15, 2021 11:34 am

Thanks for the fossilization link.

HIV enables lots of oportunistic bacterial infections, so I don’t know which one you have in mind.

bonbon
Reply to  John Tillman
January 16, 2021 2:41 am

“In 1993 HIV co-discoverer Luc Montagnier reported on cell-wall-deficient (CWD) bacteria which he called “mycoplasma” in AIDS tissue. He suspected these as a necessary “co-factor” for AIDS.”

Opportunistic was the wrong term. These turn up in various images.

bonbon
Reply to  John Tillman
January 16, 2021 3:10 am

And I just came across this :
https://en.wikipedia.org/wiki/Mycoplasma_laboratorium
“Since the genome of JCVI-syn3.0 is novel, it is considered the first truly synthetic organism”.

Even then it looks like they took a living organism and completely replaced its genes.

Curiouser and curiouser…

John Tillman
Reply to  bonbon
January 18, 2021 2:59 pm

That line of enquiry is separate from efforts to make protocells from scratch.

Antonio Moretti
Reply to  bonbon
January 18, 2021 8:22 pm

Are we attempting to lead to a conspiracy theory here? 😉

Hum
January 15, 2021 7:08 am

“May”. And bats “may” fly out of your butt John. I see you failed to mention the complexity of a eukaryote cell.

John Tillman
Reply to  Hum
January 15, 2021 8:32 am

Which structures in eukaryotic cells do you find too complex to be explained?

The origin of mitochondria and chloroplasts is satisfactorily explained by endosymbiosis of bacteria. Other organelles derive from membranes.

Science is typically couched in probabilistic terms, since the whole method is based upon doubt. Hypotheses can be shown false, but no matter how many times confirmed, certainty is rare. Science isn’t religion, based upon faith.

RegGuheert
Reply to  John Tillman
January 15, 2021 1:53 pm

“Anyone who has been seriously engaged in scientific work of any kind realizes that over the entrance to the gates of the temple of science are written the words ‘Ye must have faith.’” – Max Planck

bonbon
Reply to  RegGuheert
January 16, 2021 3:35 am

I might add Einstein’s comment “the most incomprehensible thing about the universe, is its comprehensibility”.
Thus faith is necessary. That a hypothesis, comprehensible, can work at all is impossible to “explain” – except that we actually do that.
“Doubt” and probability are but pale shadows….

John Tillman
Reply to  RegGuheert
January 18, 2021 2:58 pm

Faith isn’t required for science. Just the reasonable assumption that the rules which presently govern the universe haven’t changed since its beginning. Scientists constantly test this hypothesis and have not as yet found it wanting, as for instance in radioactive decay rates.

Planck’s comment is here taken out of context, as is sadly typical of creationist mendacity.

John Tillman
Reply to  John Tillman
January 18, 2021 3:25 pm

Planck:

“The faith in miracles must yield, step by step, before the steady and firm advance of the facts of science, and its total defeat is undoubtedly a matter of time.” 

While nominally Lutheran, Planck did not believe “in a personal God, let alone a Christian God”.

dodgy geezer
January 15, 2021 8:29 am

we eukaryotes…

I never thought of myself as an eukaryote. I always thought of myself as a colony of eukaryotes..

John Tillman
Reply to  dodgy geezer
January 15, 2021 9:23 am

We are multicellular eukaryotes.

dodgy geezer
Reply to  John Tillman
January 15, 2021 9:39 am

Half of my cells seem to be working against the rest. A bit like America…

Antonio Moretti
Reply to  John Tillman
January 18, 2021 8:29 pm

We are each a consortium of prokaryotes, eukaryotes and viruses – 

https://ep.bmj.com/content/102/5/257

John Tillman
Reply to  Antonio Moretti
January 19, 2021 9:52 am

True. We contain more prokaryotic cells than our own eukaryotic body cells. Within us and without, we swim in a sea of microbes. Viruses in our mucous are part of our immune system. Our own genome contains retroviral genetic material.

But phylogenetically, we’re eukaryotes.

Antonio Moretti
Reply to  dodgy geezer
January 18, 2021 8:29 pm

We are each a consortium of prokaryotes, eukaryotes and viruses – https://ep.bmj.com/content/102/5/257

Last edited 1 month ago by Antonio Moretti
bonbon
January 15, 2021 8:50 am

“There is growing support for according Family Mimiviridae, aka “Giant viruses”, the status of living organism, rather than mere “replicant” among the many sub-alive “Mobile Genetic Elements”. They are large, double-stranded DNA viruses.”

This is getting quite similar to a spectrum – from abiotic to biotic. Like Zeeman splitting of solid-state energy levels or the spectrum of Solar plasma hot-spots used to estimate the magnetic field.. Sounds to me as if the Biosphere, as some kind of principle, is acting on these processes. I wonder what happens when the Biosphere “weakens” which looks like “mass extinction”. Could it be viruses then play an extremely important role – mitochondria are as you say a real success story?
What about chloroplasts and viruses, another success story?

Interesting update!

bonbon
Reply to  bonbon
January 15, 2021 9:26 am

As to “spectrum”, I strongly recommend checking Chapter 8.6 of “Undivided Universe” by Bohm and Hiley, where one finds this (much QM involved) :
“Even if such objects are suspended in liquids or gases, the possibilities of interference will be limited because their mobilities are so low. It is clear that there will be an interesting area of study in the mesoscopic range, between the classical and quantum domains. It is perhaps significant that in this range the simplest forms of life are to be found.Of course if we try to use precise measurement to observe the behaviour of such objects, they will be put into well-defined positions and will behave essentially classically, provided that they are heavy enough so that their wave packets do not spread significantly during the period of the experiment. This means that the study of the mesoscopic region will require more subtle means than can be provided by exact measurements of the usual kind.”

This entire discussion is in the “mesoscopic” scale. What some dismiss as quantum effects are not trivial at this scale. It cannot be a coincidence that “life” or “Mobile Genetic Elements” are all at this scale.

Might it be possible someday to actually measure, subtley, the living quality of such elements?

John Tillman
Reply to  bonbon
January 15, 2021 11:40 am

There is arguably a continuum between complex organic chemical compounds and life. At least some viruses could be considered living, unlike other Mobile Genetic Elements, such as transposons (jumping genes), plastids and viroids (the smallest infective agents: short, circular, single strands of RNA, without a protein coat).

Antonio Moretti
Reply to  bonbon
January 18, 2021 8:31 pm

Not quite as universal as panpsychism though.

Toto
January 15, 2021 12:02 pm

Interesting and that link at the end about the placenta is even more interesting.
https://whyy.org/segments/the-placenta-went-viral-and-protomammals-were-born/

John Tillman
Reply to  Toto
January 18, 2021 2:55 pm

I’d say proto-placentals rather than proto-mammals. Proto-mammals were still egg-layers.

gringojay
January 15, 2021 5:22 pm

Going back in time the Mimi-virus scaffold has been postulated to come from the ancestor of mitochondria. What were to become Mimi-viridae most likely had a shorter DNA genome, which is thought to have undergone some genetic fusion with something akin to Rickettsia (resulting in the longer genome DNA researchers currently find).

Mega-viruses (ex: Mimi-virus) existence is speculated upon in (2018) “Giant viruses as protein-coated amoeban mitochondria?” Free full text available on-line.

John Tillman
Reply to  gringojay
January 18, 2021 2:54 pm

That’s an exciting hypothesis, increasingly supported. DNA viruses probably arise from different origins, unlike RNA viruses, which appear to show common descent from a single, primordial ancestor.

Antonio Moretti
Reply to  gringojay
January 18, 2021 9:34 pm

Not quite on topic but this ‘Giant Endogenous Viral Elements’ article just arrived in my inbox:

In Brief

Published: 10 December 2020

VIRAL INFECTION

Hidden viral giants
Andrea Du Toit 

Nature Reviews Microbiology volume 19, page 74(2021)

Numerous viruses have integrated their genetic material into host genomes, and such endogenous viral elements (EVEs) are prevalent in eukaryotes. Most EVEs that have been recognized in eukaryotic genomes to date are small genomic regions derived from retroviruses, but the prevalence of larger EVEs is elusive. Moniruzzaman et al. assessed the endogenization of nucleocytoplasmic large DNA viruses (NCLDVs, a group of eukaryotic viruses that includes ‘giant viruses’) in diverse green algae. They identified giant EVEs in a large proportion of the surveyed genomes, which could be classified into the Mimiviridaeand Phycodnaviridae families. Further data confirmed that the giant EVEs are endogenized components of the host genomes. The widespread integration of NCLDVs into the genomes of green algae is indicative of their crucial role in eukaryotic genome evolution.

References
Original article

  1. Moniruzzaman, M. et al. Widespread endogenization of giant viruses shapes genomes of green algae. Nature 588, 141–145 (2020)
John Tillman
Reply to  Antonio Moretti
January 19, 2021 9:55 am

Thanks!

Our genome contains about 8% retrovirus material. No telling yet how much from other viruses.

Joel O'Bryan
January 15, 2021 7:45 pm

Ribosomal RNA is tRNA.”

rRNA.

transfer RNAs are tRNA, they shuttle (transfer, IOW) an amino acid loaded RNA messenger to the ribosome. there is unique tRNA for every aa-coding codon except stop codons.

John Tillman
Reply to  Joel O'Bryan
January 18, 2021 2:52 pm

True, of course, but rRNA is tRNA in origin, not mRNA.

Joel O'Bryan
January 15, 2021 7:55 pm

Even bacteria have viruses, we call them phages or bacteriophages. Phages play very important roles in bacteria ecology. Every eukaryotic living cell that has nucleus is susceptible to a virus. Our red blood cells are anuclear though, and are not susceptible to virus attack (thankfully).

Parasitic genetic elements evolve naturally as a a consequence of genetic coding either RNA or DNA. All are very ancient. They arise in every order system of life, becasdue life has a coding pattern that can be co-opted by parasitic elements, and because they (parastic genetic elements) can arise, they do becasue of the fantastically large numbers of genetic copies made by all living things..

It is simple probability when you’re dealing with the fantastically large numbers that millions of copy creations by every cell by every organism across deep time.

Our genome, and the genomes of every living Eukaryote arte littered with non-functional and functional mobile genetic elements that may have been retro viruses at one point, some may have important roles, many others are probably junk.

John Tillman
Reply to  Joel O'Bryan
January 18, 2021 2:51 pm

Lots of human endogenous retroviruses (HERVs) in our genome:

https://www.frontiersin.org/articles/10.3389/fimmu.2018.02039/full

John Tillman
Reply to  Joel O'Bryan
January 18, 2021 3:36 pm

Phage therapy is enjoying a comeback to counter antibiotic resistant bacterial pathogens.

Antonio Moretti
Reply to  Joel O'Bryan
January 18, 2021 9:00 pm

Of course the above refers to mammalian systems. Birds, fish and other ‘lower’ organisms do have nucleate RBCs and so can be infected by viruses.

Virus-human RBC interactions are well known and there are likely many ways in which the interactions promote or enhance viral infectivity of other cell types. For example, in the human infecting Parvovirus B19V, extensive interactions have been shown with human RBCs. Between 3,000 and 30,000 virions per RBC have been found. This important interaction results in changes in virus structure and membrane integrity. However, the RBC-bound B19V was not able to actually infect susceptible cells. Rather, these observations indicate that RBCs play a significant role during B19V infection by triggering the exposure of the immunodominant virus capsid protein VP1u including its phospholipase PLA2 constituent activity required for an infection. On the other hand, the early exposure of VP1u might facilitate viral internalization and/or uncoating in target cells.

Ric Howard
January 15, 2021 11:45 pm

Very interesting article.

I don’t understand this statement:
“Ribosomal RNA is tRNA.”

Are you saying Ribosomal RNA (rRNA) and Transfer RNA (tRNA) are the same thing, or that rRNA is “made out of” tRNA, or what. None of the meanings I could think of for that statement jive with my limited understanding from Google, Wikipedia, etc.

Ric

John Tillman
Reply to  Ric Howard
January 18, 2021 2:48 pm

Ribosomal RNA is tRNA, wadded into the large and small ribosomal elements. It doesn’t surprise me that this discovery can’t easily be found in Google or Wikipedia, yet it’s a fact.

https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Boundless)/7%3A_Microbial_Genetics/7.06%3A_Translation%3A_Protein_Synthesis/7.6A%3A_Processing_of_tRNAs_and_rRNAs

This observation obviously has important implications for the origin of cellular life.

January 16, 2021 7:21 am

Mitochondria almost certainly derive from endosymbiosis of an alphaproteobacterium by an Asgard archaeon.

I am researching evolution for more than 15 years. There is still NO proof of any kind for this theoretical possibility, even if it has been reported as so.
So the next logical step was that which is mentioned in the article – but “forgetting” that eukaryotic nuclei consists of much more than a virus could ever bring with it. And there is no method or function forseeable which could have given today’s nuclei their complexity and functions, nor any evolutionary development, as biochemics are not in favour of it (to put it nicely and simple).

This is just a hypothesis, nothing more. Not prooven, not in the least. It’s in fact more like a thought experiment by people who try to come up with new ways to explain the unknown.
This goes for both, mitochondria and nuclei.

John Tillman
Reply to  Chris
January 18, 2021 2:43 pm

I guess you didn’t read the evidence for the viral origin of the nucleus.

No hypothesis other than endosymbiosis explains all the observations of mitochondria.

Science doesn’t do “proof”. It works by testable predictions confirmed or shown false. Predictions based upon the hypothesis of bacterial origin of mitochondria has been repeatedly confirmed and never shown false.

OTOH, there is no evidence whatsoever against the endosymbiotic origin of mitochondria and less extensively confirmed viral origin of nuclei.

Antonio Moretti
Reply to  Chris
January 18, 2021 9:09 pm

‘Proof’ (bad term) in science is usually an iterative process involving sequential, parallel and orthogonal research culminating in a ‘best yet’ aggregation of data and evidence to explain phenomena. Here’s a review of some evidence that you ought, as an ‘evolution researcher’ to be aware of, or could easily find in the literature:

https://www.sciencedirect.com/science/article/pii/S096098221731179X

John Tillman
Reply to  Antonio Moretti
January 19, 2021 9:59 am

Good paper. Thanks!

John Tillman
Reply to  Antonio Moretti
January 19, 2021 10:00 am

For some reason, I can’t rate your comment up.

John Tillman
Reply to  Chris
January 19, 2021 9:58 am

Fall,ing for creationist lies is not researching.

COwho
January 16, 2021 4:02 pm

Only recently did I stumble upon the term “giant virus.” (Wikipedia). Interesting stuff, biology! Also recently saw the term “African Penguin” and thought it was a joke. But again, Wiki to the rescue. Yes, they are real…

John Tillman
Reply to  COwho
January 18, 2021 2:39 pm

You bet! The Namib Current is cold, making penguin-friendly habitat in SW Africa.

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