[HN Gopher] Mitochondria and the origin of eukaryotes
___________________________________________________________________
Mitochondria and the origin of eukaryotes
Author : Tomte
Score : 142 points
Date : 2022-06-18 11:51 UTC (11 hours ago)
(HTM) web link (knowablemagazine.org)
(TXT) w3m dump (knowablemagazine.org)
| Koshkin wrote:
| If you are curious about these things, do yourself a favor and
| dive into Alberts et al. _Molecular Biology of the Cell_. I can
| 't recommend it enough.
| feet wrote:
| Very solid text book +1
| wrycoder wrote:
| Alberts et al. Essential Cell Biology is a bit less advanced,
| but I'm finding it very complete, just not quite so exhaustive
| (pun intended). It's still 700 pages, so you'll get your
| money's worth (if you buy a used copy).
| [deleted]
| sonicggg wrote:
| Evolution did a terrible job there. So many diseases linked to
| mitochondrial dysfunction nowadays. We have this amazingly
| complex machinery, and a single point of failure, no redundancy
| whatsoever.
| lock-the-spock wrote:
| An accessible and incredibly insightful read 100% on this topic
| is "Power, Sex, Suicide: Mitochondria and the Meaning of Life"-
| despite the flashy title a thorough scientific read and analysis,
| working through various possible arguments and teaching
| fundamentals along the way.
|
| My favourite book I read in the past five years or so
|
| https://en.wikipedia.org/wiki/Power,_Sex,_Suicide
| aesch wrote:
| I haven't read that one but after reading The Vital Question I
| will recommend anything with Nick Lane's name on it. There are
| very few people who have thought about the origin of life as
| deeply as he has.
| code_biologist wrote:
| Read it as soon as you have the time. It is every bit the
| equal of The Vital Question.
| soramimo wrote:
| Thanks for sharing, just ordered.
| alangibson wrote:
| > For billions of years after the origin of life, the only living
| things on Earth were tiny, primitive cells resembling today's
| bacteria
|
| I've often used this "fact" as an argument against complex
| extraterrestrial life. Glad to see it might be wrong after all.
| griffzhowl wrote:
| Nothing in the article contradicts that 'fact'. The question is
| only whether the development of eukaryotes involved other
| significant steps in addition to the mitochondrial
| endosymbiotic event, or whether the latter event was all that
| really mattered. In both cases, subsequent development of
| eukaryotes and hence multicellularity depended on the seemingly
| very rare endosymbiotic event.
| majkinetor wrote:
| This is Nick Lane's argument - that complex cell happend only
| once on Earth (no convergent evolution) via this symbiotic
| accident and hence it's highly improbable if not almost
| impossible.
|
| As usual, people always seem to foreget that in this universe,
| what happened once, happens all the time and we are not
| special.
| prox wrote:
| And that is if there is only one universe, which might not be
| so special as well.
| ssl232 wrote:
| Nick Lane's book The Vital Question is a masterpiece. I
| reckon he's figured out the origin of life there. I hope he
| gets on some podcast like Lex Fridman to talk about it all,
| because his ideas are just waiting to explode into the public
| imagination.
| aesch wrote:
| He was just on Sean Carroll's podcast Mindscape, good
| listen: https://www.youtube.com/watch?v=9IZ_CVu2M68
| marcosdumay wrote:
| > that complex cell happend only once on Earth
|
| Well, it's quite possible that once it happens, it voids any
| chance of it happening again just because life filling that
| niche already exists. If so, it only happens once, and this
| says absolutely nothing about the odds of that first
| occurrence.
|
| > what happened once, happens all the time
|
| That's a fallacy people do all the time here when talking
| about exobiology. It's basically states that all small
| numbers and all big numbers are alike, and that all small
| numbers are like the inverse of all big numbers.
| zeroonetwothree wrote:
| Most other features evolved independently several (or even
| many) times so this is not a good argument. It's not as if
| once there was a eukaryote it instantly spread across the
| whole planet, taking up every ecological niche. Even today
| eukaryotes don't exist in certain environments.
| alangibson wrote:
| We're all just speculating given that were stuck at sample
| size = 1 until we develop near light speed travel.
|
| I get the convergent evolution point, but so far the story is
| that 1) life arose very quickly 2) then proceeded to do very
| little for billions of years. If that's true, then it's bad
| news for the possibility of complex life being common.
| majkinetor wrote:
| It only means that complex life is less frequent then
| single cell life, not that it is uncommon.
| Qem wrote:
| > 1) life arose very quickly 2) then proceeded to do very
| little for billions of years.
|
| This is understating the feats of unicelular life. Those
| tiny organisms essentially terraformed the whole planet in
| those billions of years, oxidizing nearly all the iron
| close to earth surface, burying most carbon and then
| pumping so much oxygen in the atmosphere that at a point it
| comprised 30% of Earth gaseous envelope by weight. I
| wouldn't call that very little. To come close we'll need at
| least to terraform Mars or Venus, to match the feats of our
| microbial forebears.
| tomrod wrote:
| Single-celled life is complex. It has the same length of
| evolutionary time as multicellular life.
|
| We know very little about modes of sentience with N=1. Perhaps
| life is generally mutualistic.
| photochemsyn wrote:
| The rise of free atmospheric oxygen and oceanic dissolved
| oxygen levels were almost certainly a requirement for the
| development of complex multicellular life. Using oxygen as the
| electron acceptor in respiration means far more energy can be
| extracted from reduced fuel molecules (sugars, fats, amino
| acids, methane, hydrocarbons, ammonia, etc.) than by using
| species like oxidized sulfur and iron, CO2, or nitrate (NO3)
| for that role.
|
| This is really where the mitochondria come into play, as they
| allowed their host to utilize oxygen for this purpose. This can
| be seen by looking at modern eukaryotes that have reverted back
| to an anaerobic lifestyle:
|
| > "In lineages of eukaryotes adapted to low oxygen conditions,
| mitochondria have been drastically reduced, functionally
| altered and, in one case, completely lost."
|
| "The Origin and Diversification of Mitochondria (2017)"
|
| https://www.cell.com/current-biology/pdf/S0960-9822(17)31179...
|
| Hence, looking for the signature of free oxygen in the
| atmosphere of exoplanets orbiting distant stars is considered
| to be a fairly good indicator of the possibility of complex
| multicellular life of some sort, and at least of an active
| photosynthetic microbial ecosystem.
|
| (Incidentally, the historical divisions withing academic
| university departments led to evolutionary biology generally
| ignoring the importance of early Earth's geochemistry in the
| evolution of life, as they saw evolution as a kind of
| cellular/organismal process divorced from the physical
| surroundings - the latter being the province of the geology
| department. The renewed interest in exobiology and origin-of-
| life research has tended to bridge this gap.)
| alangibson wrote:
| The way I read that is that developing complex life is even
| more contingent than 'just wait long enough'. Given what we
| know for sure, you need rather narrow concentrations of
| specific gasses at least.
| simonh wrote:
| It's not wrong, at least I don't think this article is arguing
| that multi cellular life evolved any earlier than we thought.
| Just that the mechanisms were different than we expected.
| pmags wrote:
| For those interested but new to role of endosymbiosis in
| evolution, it's useful to keep in mind that there's strong
| evidence of an endosymbiotic origin of chloroplasts, another
| major event in the history of life. Here's a recent review
| article that highlights some of the key evidence and outstanding
| questions:
|
| Sibbald SJ, Archibald JM. Genomic Insights into Plastid
| Evolution. Genome Biol Evol. 2020 Jul 1;12(7):978-990. doi:
| 10.1093/gbe/evaa096. PMID: 32402068; PMCID: PMC7348690.
| csr86 wrote:
| How the children inherited the swallowed organism?
| majkinetor wrote:
| Bacterial division would get some mitos on either side of the
| dividing cell. Mitos then proliferate on its own.
| frostburg wrote:
| Presumably like we do - (I'm heavily simplifying the complex
| regulation involved) the mitochondria have their own DNA which
| gets duplicated when the cell prepares to undergo mitosis, then
| the two new cells split the results.
| anton96 wrote:
| Does that implies that mitochondria also had to evolve at
| some point to detect duplication of their host cell so they
| duplicate at the same time?
| reubenswartz wrote:
| There are lots of mitochondria in a cell (almost always,
| ignore red blood cells, for example), and the mitochondria
| have their own mechanisms for detecting when they need to
| divide (exercise and the resulting stress being one of
| them, which is why working out makes you more fit).
|
| Also note that the DNA for most of the mitochondrial
| proteins is in the host cell's nucleus-- the mitochondrial
| DNA is stripped down to coding for just a few essential
| proteins.
| Linda703 wrote:
| anuvrat1 wrote:
| How simple are Prokaryotic Cells really? Like "simple" enough
| that we understand all the intricate workings of it, or "simple"
| enough to be made from scratch?
| david_l_lin wrote:
| Honestly, neither. Biology is complex and messy, and often not
| at all intuitive.
| Daniel_sk wrote:
| Imagine giving a scientist in 1900 a modern CPU. He may be able
| to disassemble and study it, but it's impossible to make it
| from scratch because it takes a chain of steps that lead to
| complicated modern factories that then produce the chip. It's
| hard to skip those steps. We can swap DNA in living cells and
| produce modified cells, but we lack the tools to create such
| complicated and microscopic structures in a pure synthetic way.
| wheelerof4te wrote:
| A neat fairy-tale but, with all due respect, scientist don't know
| anything that happened a billion+ years ago.
|
| This is a little more than a tabloid article.
| ncmncm wrote:
| If they find cells lacking some organelle, it will be hard to say
| whether it was never acquired, or was later abandoned.
|
| One clue would be leftover genes from when it was there.
| Eukaryotes often find it hard to prune out excess DNA, vs. just
| turning it off.
| edgyquant wrote:
| DNA doesn't help as much as you think with single celled
| organisms thanks to HGT. Bacteria, at least, share DNA and thus
| we can't use it to determine a linear evolutionary sequence.
| ncmncm wrote:
| Eukaryotes don't do so much of that.
| jjtheblunt wrote:
| HGT?
| [deleted]
| reubenswartz wrote:
| Horizontal gene transfer.
|
| Because biology isn't complicated enough. :)
| 323 wrote:
| > _If they find cells lacking some organelle_
|
| A most famous example is red blood cells, which are emptied of
| most organelles to make space for hemoglobin.
| [deleted]
| CRUDite wrote:
| If we assume single celled life is common, and exists in either
| all star systems, or in all systems without a hot Jupiter close
| to the star; then given the length of time involved here before
| eukaryotes, can we estimate how many planets in the galaxy have
| eukaryotes? Or how long it will be before some do? Presumably
| increasing the length of time increases the probability of
| occurrence as would increasing the number of stars involved.
| Though how can we know if the event was statistically likely
| after that amount of time or whether we are deviations from the
| centre of the distribution (other than observing the quiet
| galaxy). Surely we can have a rough idea now of where we stand
| JumpCrisscross wrote:
| > _can we estimate how many planets in the galaxy have
| eukaryotes?_
|
| Not yet. In the history of life on Earth, this has happened
| once. Knowing what we know about cellular biology, it's
| stupidly unlikely. Beyond our present theories' ability to
| quantify.
|
| By the way, I think this is one of--if not the--great filters.
| It's unlikely to happen, to not promptly get smote by its
| primordial planet's tantrums and to get it so right it
| perpetuates for billions of years.
| echelon wrote:
| > Not yet. In the history of life on Earth, this has happened
| once.
|
| 1) That we know about.
|
| 2) Not unlike startups vs. established business, any newly
| emerging "eukaryotes" have to out-compete the already-evolved
| incumbents, which are already quite good at harnessing
| energy. You're much more likely to find success in business
| than in an entirely new evolutionary branch, though I doubt
| biological "gray goo" is outright impossible [1].
|
| [1] Reverse chirality autotrophs sound like a scary sci-fi
| novel plot https://news.ycombinator.com/item?id=28038505
| ajuc wrote:
| Additionally the environment changed significantly since
| then (for one example oxygen which was highly toxic to most
| forms of life that existed back then is now over 20% of
| atmosphere).
|
| > Reverse chirality autotrophs sound like a scary sci-fi
| novel plot
|
| Very ice-9-like.
| yyyk wrote:
| >Reverse chirality autotrophs sound like a scary sci-fi
| novel plot
|
| I doubt this. 'Not being digestible' is very far from
| 'being invulnerable' or even 'being able to spread
| quickly'. The kingdom of life has many ways to kill stuff,
| ways which don't care about chirality, and our typical
| R-sided lifeforms have all the evolutionary 'motivation' to
| come up with new ways just the off the competition. That's
| before humans get into the picture, which we have the tech
| to do.
|
| There may be an accumulation of non-digestible stuff until
| nature reaches a balance. However, there's a very large
| recent accumulation of non-digestible materials called
| 'plastics', and while somewhat harmful, they're not a life-
| ending threat. Nature is already finding ways to process
| these materials[0].
|
| [0] https://en.wikipedia.org/wiki/Plastic_degradation_by_ma
| rine_...
| echelon wrote:
| Sure, but I did say "sci-fi". And I think there are a lot
| of unaddressed points.
|
| Plastics don't self-manufacture. You might not be able to
| control the rate.
|
| Just because you kill something doesn't mean you break
| down its carbohydrates. Reverse chiral organism skeletons
| could bioaccumulate and we could have a situation similar
| to the Carboniferous.
|
| Someone might be able to synthesize a bacteria in the lab
| given enough time and effort from an organism that
| proliferates quickly. It doesn't have to capture all the
| carbon. Just out-compete a keystone species. Plankton,
| mycorrhizae, etc. Or attack a large percentage of the
| plant biomass.
| yyyk wrote:
| >Plastics don't self-manufacture. You might not be able
| to control the rate.
|
| The rate is limited by the process. Since no precursors
| exist, it must 'self-manufacture' from scratch. This has
| inherent limits even before introducing competition for
| food, poison, predators that eat you even despite them
| not being able to really digest, etc.
|
| >Just because you kill something doesn't mean you break
| down its carbohydrates. Reverse chiral organism skeletons
| could bioaccumulate and we could have a situation similar
| to the Carboniferous.
|
| So you don't break it down. Nature will have plenty of
| time to adapt. Humans will step in if needed.
|
| >Someone might be able to synthesize a bacteria in the
| lab given enough time and effort from an organism that
| proliferates quickly.
|
| That's an incredibly messy way - create an entire
| L-chiral biochemistery - to get a weapon which doesn't
| have a setting between 'kill everything' and 'do rather
| little' (IMHO, the second being much likelier). There are
| far worse and more directed things one can do with a lab.
| Even the absurd 'kill everything' goal is far more likely
| to be reached in different ways.
| sterlind wrote:
| per the article, endosymbiosis has happened a bunch of times.
| multiple different kinds of chloroplasts, several
| prokaryotes, a parasite etc.
|
| this was all when eukaryotes engulfed prokaryotes, but still,
| how does this mean unlikely? it seems imminently likely,
| since.. it happened a bunch of times.
|
| seems to me like prokaryotes evolve a strategy of engulfing
| others for their resources, then one day engulf a prokaryote
| infected by a virus, which transfers DNA across, rinse and
| repeat.
|
| how is this more of a filter than abiogenesis?
| simonh wrote:
| The thing that only happened once on Earth and that's a
| prerequisite to developing complex life forms is not
| endosymbiosis, it's life going multi-cellular. They are not
| the same thing.
|
| Endosymbiosis is not identical with going multi-cellular,
| and it seems that all but perhaps one of the known
| instances of endosymbiosis didn't play any role in us going
| multi-cellular anyway. In fact this article makes the case
| that it may not have been critical at all.
| gus_massa wrote:
| Multicellularity looks relatively easy. From https://en.w
| ikipedia.org/wiki/Multicellular_organism#Occurre...
|
| > _Multicellularity has evolved independently at least 25
| times in eukaryotes, and also in some prokaryotes, like
| cyanobacteria, myxobacteria, actinomycetes, Magnetoglobus
| multicellularis or Methanosarcina. However, complex
| multicellular organisms evolved only in six eukaryotic
| groups: animals, symbiomycotan fungi, brown algae, red
| algae, green algae, and land plants. It evolved
| repeatedly for Chloroplastida (green algae and land
| plants), once for animals, once for brown algae, three
| times in the fungi (chytrids, ascomycetes and
| basidiomycetes) and perhaps several times for slime molds
| and red algae._
| simonh wrote:
| It's relatively easy once you have evolved the
| biochemical infrastructure to support it, but on Earth
| that took several billions of years to achieve. There's
| no way around it, no amount of hand waving how easy it is
| negates the fact it took billion years of evolution to do
| it.
|
| Also most of those forms of multicellularity are
| extremely basic, little more than tangles or sheets of
| cells, even after hundreds of millions of years of
| further evolution. That's not likely to get to
| intelligent life.
| JumpCrisscross wrote:
| > _how is this more of a filter than abiogenesis?_
|
| Common chemistries get us very close to molecular systems
| subject to evolutionary pressure. (Simplest: RNA world
| hypothesis.) We are missing links. But the pathway is
| plausible.
|
| Chloroplasts, as you mention, are a potent counter
| argument. But once you have surplus cellular energy,
| additional endosymbiosis has a lower threshold. Based on
| current research, all life has a similar mitochondria.
| Different kingdoms didn't nom their own and go. That
| uniqueness suggests difficulty.
| kylebenzlee wrote:
| Yes, this (nonsense) discuassion is when you have computer
| progammers discuss biology. Is strange because they know
| nothing but all seem to think they must be experts of
| evrything because they get paid a lot to sit infront of a
| computer all day.
| marcosdumay wrote:
| Well, that's not a good assumption to make. Our most capable
| life detector1 is analyzing the atmosphere of planets, captures
| stuff similar to our simplest single celled life. So, it's not
| a good guess that it's common.
|
| 1 - Actually our second best. The best one is the fact that
| nobody colonized Earth before we existed, that is tuned in
| space-faring life.
| kylebenzlee wrote:
| 323 wrote:
| You make a big assumption, that there must be only two kinds of
| cells, "simple" and "complex", like on earth.
|
| That could well be an accidental fact. Maybe on some planets we
| have a gradient of cell complexity.
|
| Also, we don't really know what even simpler kinds existed on
| earth but were lost, since bacteria, the "simple" kind, it's
| obviously too complex to have been the first ever life form.
| andrewflnr wrote:
| That's not even true on earth. Archaea exist, and eukaryotes
| span a pretty wide range of complexity themselves.
| lkrubner wrote:
| Maybe, but there are other narratives that are easy to spin.
| Our solar system has 3 planets all of which might have had
| single-celled organisms, at some point: Venus, Earth, and Mars.
| And for the first 3.7 billion years, the 3 planets might have
| followed a similar path. And then all 3 planets reach old age
| and basically die, Venus becoming too hot, while Earth and Mars
| become mostly dead ice covered snow balls. And maybe that is
| the normal history of most planets, even planets that develop
| single-celled life.
|
| In that narrative, the emphasis is on the extraordinary re-
| birth of Earth, after the end of Snowball Earth. Almost
| everything that we regard as interesting about Earth happens
| after this late-in-its history revival. That raises some other
| questions, such as, why did Snowball Earth end? Why does
| multicellular life take off then, but not before? What is it
| that makes the Earth/moon system so unusually dynamic that it
| hasn't settled down to some dead equilibrium, even after 3.7
| billion years? What allows Earth to have such an extraordinary
| additional era?
___________________________________________________________________
(page generated 2022-06-18 23:00 UTC)