Marine bacteria genus may hold mitochondria's closest relatives
aaas.org
aaas.org
To be picky: that's only 99.9...% true, because some have lost them again, like Monocercomonoides and Henneguya zschokkei. And they lost the mitochondria by two different mechanisms!
https://en.wikipedia.org/wiki/Monocercomonoides https://en.wikipedia.org/wiki/Henneguya_zschokkei
EDIT: typo
Rafflesia (a parasite) might have lost the entire chloroplast: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3969568/
Here's one 'in the middle' that lost a bunch of genes from the chloroplasts: https://journals.plos.org/plosone/article?id=10.1371/journal...
Bonus, dodder plants also seem to be able to double as a sort of above-ground mycorrhizal network, allowing plants (even across species) to communicate with each other and send warning signals about pests/stressors/etc
In siphonophores, each specimen is actually a colony of minute asexually reproducing organisms called zooids that have to work together for survival. They are not "independent" in the sense that they would die without each other, but given the fact that they can reproduce independently, there's definitely some sort of independence there. It's like if all your organs were able to independently reproduce themselves.
Eukaryotic cells have multiple copies of their mitochondria, not one. When the cell divides, the mitochondria (roughly) split between the two daughter cells then carry on
For me, the intuitive part is how mitochondria can be created by the body if it's an external structure that's been found. If I take a coin and put it in my pocket, my children don't have any coins at birth. They have to find one themselves. Why is it different for mitochondria?
But to continue the analogy, it's more like you split yourself into two smaller "you"s, and in the process each new "you" gets half a coin in the pocket of each new "you".
An interesting thing about mitochondria too— we receive all of our mitochondria from our mother. So for every human, there is an unbroken line of direct mitochondrial ancestors leading all the way back to the first biologically unique Homo Sapian women
The piece I was missing is that even for large organisms, new life is created by cells (eggs) already containing mitochondria dividing. New cells aren't created from scratch.
: Mitochondrial replication is controlled by nuclear genes and is specifically suited to make as many mitochondria as that particular cell needs at the time.
: Each human cell contains approximately 100 mitochondria
: The amount of mitochondria per cell also varies by cell type
: Egg cell: Mature metaphase II egg cells can contain 100,000 mitochondria
(so when it comes to passing down mitochondria to descendants, eukaryotes don't fool around)
And shockingly, it worked! The engineered bacteria replaced the natural mitochondria in the yeast. Wild.
But I guess to answer your question more directly, the cells that don't have the mitochondria would more likely die, because they don't have the fitness advantage.
It would be even more miraculous if the cell managed to relate interlopers to just one side for the event. Although you're kind of getting away from cell fission at that point: that's more like birth.
Goodreads: https://www.goodreads.com/book/show/39001.Power_Sex_Suicide
Over this past weekend on Saturday afternoon (ET, NYC + PHL markets)[1] on an NPR station (in the car) I heard what I presume was a rebroadcast of a show on a theory about the creation of the first multi-cell organism. Typically, I pick up the name of the show and who the featured guest was, but this time I missed both. It was fascinating stuff and would like to listen to it in full.
Does this ring a bell with anyone?
[1] I realize each NPR station has its own schedule so this clue might not be helpful.
https://www.npr.org/2011/08/10/139345519/scientists-explore-...
Still. Thanks. The whole concept is ridiculously beyond comprehension.
So I guess I want to say that you're asking the wrong question.
To illustrate, here's a list of different classes of antibiotics, examples, and how they work: https://arpsp.cdc.gov/resources/OAU-Antibiotic-Class-Definit...
And here is a visualization: https://i0.wp.com/www.compoundchem.com/wp-content/uploads/20...
DNP is an example of a drug which selectively targets mitochondria. It makes people burn to death from the inside out.
The survival of eukaryotes may be so unlikely as to even partially explain Fermi paradox.
Archaeopteryx lived in the Jurassic, so it's not really possible that chicken descended from the T Rex. They're cousins though.
Archaeopteryx is offshoot in the evolutionary path leading to birds. It shares a common ancestor with modern birds but branched off in a direction that did not lead directly to them.
https://www.pnas.org/doi/full/10.1073/pnas.1421402112
> The evolution of life on earth has been driven by a small number of major evolutionary transitions. These transitions have been characterized by individuals that could previously replicate independently, cooperating to form a new, more complex life form. For example, [...]
I heard another theory that it was actually the archea that engulfed the pre-mitochondria rather than the it accidentally finding itself inside an archea. There's some kinds of archea that occasionally grow some extracellular "appendages" and it's conjectured that it may have had some kind of more typical symbiotic relationship with the two kinds of microbes living in near physical contact. What could have happened is that the archea gradually came to fully engulf the protomitochonria with the appendages evolving into being the full body of modern eukaryotes with the nucleus evolving from the functions that were part of the main archean cell body. Some functions got shuffled between the three compartments as this became more of an obligate relationship.
- Power, Sex, Suicide for a general overview and history of mitochondria (did you know that Lynn Margulis, main proponent of the endosymbiont theory, was once married to Carl Sagan?!?)
- The Vital Question on restraints on life due to the biochemistry of mitochondria
Both highly, highly recommended.
It was surely an experiment attempted many times, as countless bacteria infected countless protoeukaryotes. Probably doesn't explain Fermi paradox, as it succeeded at least twice here on Earth. One for mitochondria, another for chloroplasts.
1) Mitochondria have their own DNA, which is circular and similar to bacterial DNA. This DNA is distinct from the DNA in the nucleus of the eukaryotic cell.
2) Mitochondria have their own ribosomes, which are smaller and structurally different from cytosolic ribosomes. These ribosomes are responsible for translating mitochondrial DNA into proteins.
3) Mitochondria have their own mechanism for protein import, which is different from the protein import machinery of the eukaryotic cell. This suggests that mitochondria were once independent organisms.
4) Mitochondria share many similarities with alpha-proteobacteria, a group of bacteria. This includes the structure of their inner membranes, the arrangement of their genes, and the way they generate energy.
5) Mitochondria reproduce by binary fission, similar to bacteria. This suggests that mitochondria once replicated independently of the eukaryotic cell.
6) The endosymbiotic theory is also supported by the fact that mitochondria are found in all eukaryotic cells, with only a few rare exceptions. This suggests that mitochondria were acquired by an ancestral eukaryotic cell and have since been passed down to all of its descendants.
8) There are multiple examples of ongoing endosymbiosis where the engulfed cell remains a true symbiont, not yet an organelle. Paramecium bursaria is my favorite - a ciliated protozoan with blue-green algae symbionts.
Bonus: there is evidence for secondary and tertiary endosymbiosis too.
If you do not understand something, it is better to respond with curiosity than dismissal. I've found that when something seems absurd to me, if I dig in to try to understand it more, it usually turns out my initial reaction was radically wrong.