Tiny microbe challenges the definition of cellular life
nautil.us
nautil.us
The article should have at least tipped its hat to mitochondria:
>But unlike a virus, Sukunaarchaeum has its own ribosomes, cellular structures that synthesize proteins, and it can replicate itself without the help of a host.
Yes and this is true of mitochondria as well: Their own DNA, a own complex set of membranes, a private customized set of ribosomal proteins and tRNAs, and the ability to replicate within the “host”. Mitochondria are also perfectly happy to be swapped from cell to cell.
I wonder if or how these nanobiobots contribute to the fitness of their hosts.
Later on archaea were discovered they are the size of bacteria but the look like the bigger cells in how some of the key things in side of them work. Archaea don't cause any known diseases so that's one of the reasons it took so long to find them, but we can now find them all over the place by their DNA and it's now pretty clear that the ancestor of all big celled (and multi cellular life) was an archaea and they've even found the group of archaea that multi cellular life evolved out of.
This does not differ that much from bacterial or fungal spores, or even from plant seeds, which can also be almost "dead", i.e. without detectable metabolism or internal changes, even over many thousands of years, until they reach a favorable environment that triggers their revival.
The difference between a virus and a bacterial spore is that the viral particle contains only a subset of the parts of a living organism, so it could never be brought back to life in an environment where nothing is already alive. However, once the virus takes control over many parts of a cell, which provide the functions that it is missing, like the machinery for protein synthesis, the ensemble formed by the parts brought by the viral particle and the parts formerly belonging to the invaded cell, can be considered as alive and distinct from what the invaded cell was previously.
In any case, the evolution of the viruses and the evolution of the cellular forms of life are entangled, with a lot of genetic material exchanged between them, so considering the viruses as non-living is definitely counter-productive, because neither the viruses nor the cellular forms of life can be understood separately.
You just proposed a definition. Good. It's not complete, but necessary, conditionally.
Basically, we shouldn't use "alive" and "dead" as dualities. There's at least three states: "dead/inert/never gonna get there", "meets a definition of life (see next category) when supplemented by a host cell or something else complex and exterior", "can self-replicate and grow on its own, in a friendly environment with sufficient food/fuel/inputs available = life".
Maybe more. But let's stop pretending biology is dead versus alive, because viruses definitely ruin that.
I always thought of a virus as purely a "modifier", not having the characteristics of "life" independently. If this was a game, the virus might be a runestone or skin for your character.
Anything that doesn't need external "life" to come alive, I would consider as "life" in various states. Maybe it's in hibernation, or stasis, or dormant but the life is there. Maybe to keep the silly game analogy, this might be the extra character on your roster.
Doesn't almost any biological entity need external life to come alive via, e.g. reproduction or mitosis or what have you?
This is why I said "to come alive" instead of "to be created". The virus is something that just exists but only becomes alive when mixed with something that's already alive.
Instead of the concepts being like a box where something is definitely in the box or not in the box like in mathematics or maybe physics, the concepts are more like a clustering of characteristics in a high-dimensional space or landscape of variation, where things are classified according to their similarity to a central paradigm case. (This seems to be how our minds model at least some concepts as well, as evidenced by our being faster at categorising cases that are closer to some paradigm case)
One notorious example is the concepts of male and female: yes, there are borderland examples of individuals who can't be classified as either, but almost everyone clusters sufficiently closely to the distinct paradigmatic cases that the concept has an obvious utility.
But the same thing happens everywhere in biological classification: whether something is a mammal or not becomes fuzzy as we go back in evolutionary time, and whether something is alive or not is similar.
The definition is fuzzy because the concept is fuzzy! Even something that we in every day life see as settled such as a species is not always clear-cut. Cat or dog? That's usually easy. Member of a species yes or no? Not so easy, and in some cases subject to considerable debate and even then unresolved.
For instance:
https://en.wikipedia.org/wiki/Species_complex
And:
https://en.wikipedia.org/wiki/Ring_species
Boundaries are hard, just like naming things.
It is misconception that hair and nails continue to grow. What happens is the that kind and soft tissues dehydrate and shrink and the hairs and whiskers stick out more. Growth stops soon after oxygen and nutrients stop being delivered.
Just like geology doesn't have a great definition for their subject of study (the earth). They have a definition that works really well, but because they only have one example, the definition ain't stress tested.
Slightly less silly: it took the discovery of lots more bodies inside and outside the solar system (dwarf planets here, exoplanets elsewhere) for astronomers to really nail down the definition of planet.
Autopoiesis and Cognition: The Realization of the Living (1980)
https://en.wikipedia.org/wiki/Autopoiesis_and_Cognition:_The...
Unfortunately out of print.
The result is a landscape of fuzzy definitions mostly centered around that last one.
> This seems to be how our minds model at least some concepts as well [...]
Since we have existed for 100's of thousands of years, and formal thinking only a couple hundred as a widespread practice, only habitually by a modern minority, and then for a tiny minority of daily concepts -- that is very nearly the only way we encode concepts.
In fact, we no doubt actually encode formal concepts using clustered characteristic thinking. We have just intentionally narrowed characteristics down to the point that the result is formal thinking.
Yes a two step.
Spoken words forced/helped us divide up completely fuzzy concepts into discretized hierarchies of less and less fuzzy concepts over time.
And then written symbols, enabled a trend of identifying more and more simple I.e “primitive” abstract concepts (culminating in true, false, 1, 2, 0, infinity, node, edge, …) that let us reformulate and better understand complex fuzzy concepts as compositions of primitive concepts.
Language and then pen/paper.
Most concepts break down on borderline cases, within and without biology. Those motivated will abuse this to argue that those concepts don't meaningfully exist at all.
Take our color perception as an obvious example: We clearly see different types of color, despite us being unsure at the thresholds in between, and the actual electromagnetic radiation of visible light being a continuous wavelength range.
That is just a fundamental limit of our reasoning. We mentally make models of the world to make sense of it. These models have to be of less complexity than reality, ergo they have to cluster perceptions, ergo we have to categorize.
And even when the attributes are discrete, phenomena tend to be highly combinatorial.
Leaving lots of room for new combinations to be discovered that will upset our taxonomies.
The definition of steel is pretty hard-edged. A polymer of C, H, and O isn't steel.
The definition of a quasar is similar. There are "maybe quasars", but that's from lack of data, not lack of definition clarity.
A circle is pretty exactingly defined. Mathematicians aren't fuzzy on that.
Viruses particularly exemplify “intelligence” is better understood as a spectrum of information-processing and adaptive behaviors rather than a strict threshold.
The issue seems to me that neither concept is wrong, but that we humans keep trying to impose absolute definitions on phenomena that exist along continua, blurring into one another in ways that resist our neat little categorizations.
I would argue viruses exemplify some of the highest evolved intelligence in our world.
PS: There's more recent work done on this:
https://www.quantamagazine.org/a-new-thermodynamics-theory-o...
Not only do I need certain physical conditions (temperature, pressure, molecular gas composition, etc), but I also need to eat, so actually me being "alive" is dependent on specific biological conditions too. My Minimum Viable Environment actually includes other organisms, yet this doesn't challenge the fact that I'm defined as alive.
Certain parasites can only live or reproduce within another organism. This is even more extreme, but it still doesn't challenge our definition of them as being "alive."
This new organism requires a specific "environment," and that "environment" happens to be inside another organism. So what? We're totally un-phased by this requirement when it occurs in other examples.
Perhaps it's better to think of this not as a spectrum between alive and non-living, but as a hierarchy of how constrained (vs unconstrained) is the "environment" required to support life processes.
Take away the mitochondria and bacteria… can cells live on their own?
If no, then are we that all that different than this microbe?
Might even be sheer arrogance to think that we are the “host” (much like cats/dogs domesticating humans). Maybe we only exist to serve the mitochondria (:->
> These flagellates are unusual in lacking aerobic mitochondria. Originally they were considered among the most primitive eukaryotes, diverging from the others before mitochondria appeared. However, they are now known to have lost aerobic mitochondria secondarily, and retain both organelles and nuclear genes derived ultimately from the mitochondrial endosymbiont genome. Mitochondrial relics include hydrogenosomes, which produce hydrogen (and make ATP), and small structures called mitosomes.
We can live without bateria if we add with some food supplements.
mitochondria isn't considered alive, as a separate organism, AFAIK. It doesn't even have a species name. It's just a component of the host cell.
As I understand it, these new microorganisms are parasites. They're not essential for the functioning of the host cell like mitochondria are.
Citation needed. I would strongly doubt that this is true, because microbes also play a very important role in eg. immune defense. Remove all the mutualitic microbes from a human (eg skin, digestive tract) and the parasitic and pathogenic bacteria will take their place immediately.
There are sterile mice made for scientific uses - 100% mouse, completely microorganism free or your money back. They have health issues, but they can survive and reproduce in the right conditions.
Of course, those "right conditions" include sterile housings and sterilized food, because they'll get contaminated otherwise.
That is interesting! Is it because they are missing functions which bacteria offers?
Ship of Theseus, obviously.
Essentially nothing can live on its own, certainly not animals.
Neither can live without the other. Too much genetic exchange has taken place in some distant ancestor where critical genes were deleted from mitochondria and moved to the host. Meanwhile host cells became utterly dependent on mitochondria for energy production. Or you might say: the mitochondria were producing so much excess ATP the host cells started evolving to depend on that much energy being available.
The exceptions are later cases (like a few organisms that have copied energy production from the mitochondria genome then later lost the mitochondria entirely).
For all purposes mitochondria are zombie archaea (not bacteria). Hollowed out empty shells retaining just enough function to perform aerobic respiration and reproduce. There is little pressure to evolve away from this local maxima. What benefit would the host cells derive from getting rid of the mitochondria? Not much. And having those critical functions isolated in what amounts to a pseudo-organelle with its own DNA protects it from a lot of sources of damage/error.
So... are we obligate symbiotes? Or have mitochondria hyper-evolved to such a point they are just organelles in our cells - just ones that carry their own DNA instead of relying on the cell's main DNA? Like much of biology... a bit of both in a fuzzy mix without a clear line.
Not of course to say these outfits are behind the decline in science reporting, but it's a real tragedy how difficult it is to find actual and competent scientific journalism today, a tragedy that makes the job of such charlatans all the easier. I'm glad that Quanta Magazine seems to be doing well enough, which certainly isn't perfect but I've read some good articles from them.
I made a similar comment in an old thread about this but I can't find it. My biology is not good enough to give details about the phylum (or whatever, I never remember the classification), but I have the same annoyment in many posts about math or physics.
I spent too long trying to figure out why dinosaurs were a part of this discussion.
I mean, I know the article mentions it "has its own ribosomes, cellular structures that synthesize proteins, and it can replicate itself without the help of a host" but that doesn't always translate to complex structures plainly visible underneath a microscope.