Bacteria and Mitochondria

[Rough_ER]

I recently heard a really awesome idea about the origins of mitochondria. I think it's fairly old but it's new to me. I don't mean to brag but I actually noticed this myself before I was told hehe.

The Cristae in a mitochondrion look so much like the mesosome of a bacterium it's unreal. It's almost as if a mitochondrion is simply a bacteria with cristae all over the inside surrounded by a fluid matrix. It even contains it's own ribosomes and it's on DNA, which as far as I know is a floating ring like in a bacterium (correct me if I'm wrong).

What I'm wanting to know is: how probable is it that the mitochondria found in eukaryotic cells originated from a bacterial invasion, followed by some sort of symbiosis? Although I don't see what the bacterium would get from it :s (Help!)

Thanks in advance for your answers!

Dave x

 

[Valjean]

This has been generally accepted by biologists for some time, as has the similar origin of chloroplasts in green plants.

Evolution occurs by many and various mechanisms.

It is facsinating that a complex multicellular organism would incorporate a complete, foreign organism into it's own genome, though, isn't it?

 

[Rough_ER]

This has been generally accepted by biologists for some time, as has the similar origin of chloroplasts in green plants.

Evolution occurs by many and various mechanisms.

Well call me Golgi.... What experiments would they have carried out to investigate this? If it is generally accepted I assume that the evidence is overwhelming....

I had never thought about chloroplasts, wow.

 

[Valjean]

Yikes!

I've long since sold my old Bio textbooks, and I'm not feeling up to hours of research in my remainig references. :sorry1:

I suggest you consult the Great God Google -- then follow the references/footnotes to the library to read the original research papers.

 

[Rough_ER]

Thanks for the help. I am unfortunately plagued with an abnormal level of technological ineptitude. I will however try my best with the googling.

 

[Halcyon]

I recently heard a really awesome idea about the origins of mitochondria. I think it's fairly old but it's new to me. I don't mean to brag but I actually noticed this myself before I was told hehe.

The Cristae in a mitochondrion look so much like the mesosome of a bacterium it's unreal. It's almost as if a mitochondrion is simply a bacteria with cristae all over the inside surrounded by a fluid matrix. It even contains it's own ribosomes and it's on DNA, which as far as I know is a floating ring like in a bacterium (correct me if I'm wrong).

What I'm wanting to know is: how probable is it that the mitochondria found in eukaryotic cells originated from a bacterial invasion, followed by some sort of symbiosis? Although I don't see what the bacterium would get from it :s (Help!)

Thanks in advance for your answers!

Dave x

It's called endosymbiosis. The prokaryotes get a safe environment in which to live and procreate (mitochondria still move about and reproduce 'independantly' within our own cells). The eukaryote gets the ATP or glucose.

http://en.wikipedia.org/wiki/Endosymbiotic_theory

 

[Djamila]

Very interesting!

Seyorni - it is fascinating that it would be part of us. Most sophisticated species rely very heavily on other, more primitive life. The bacteria in our intestinal tract, and so on. But to have something within our cells is really interesting!

 

[Rough_ER]

It's called endosymbiosis. The prokaryotes get a safe environment in which to live and procreate (mitochondria still move about and reproduce 'independantly' within our own cells). The eukaryote gets the ATP or glucose.

Thanks! I knew about the independent reproduction and all. What I was curious about was how they are more concentrated in high activity areas e.g liver cells etc. By what means is the concentration of mitochondria monitored and maintained?

 

[Gentoo]

By what means is the concentration of mitochondria monitored and maintained?

If I had to guess, I would say that it's monitered through gene regulation. A certain gene within the cell giving the information to the rest of the cell as to how many mitochondrion and other organelles and also how they function (to a degree).

 

[Halcyon]

If I had to guess, I would say that it's monitored through gene regulation. A certain gene within the cell giving the information to the rest of the cell as to how many mitochondrion and other organelles and also how they function (to a degree).

Most likely. A high proportion of the mitochondrion genome has, over time, been transferred to the eukaryote nucleus.
So, although the mitochondria are technically independent cells in their own right, they are so highly controlled by the eukaryote nucleus that they are functionally organelles.

Also, and this is just me speculating, during the early stages of embryonic development when cells are specialising, cells may split unsymmetrically - possibly more mitochondria are moved to one half of the mother cell via the cytoskeleton prior to mitosis. But i'm just postulating here, don't take that as fact or anything.

 

[Rough_ER]

Most likely. A high proportion of the mitochondrion genome has, over time, been transferred to the eukaryote nucleus.
So, although the mitochondria are technically independent cells in their own right, they are so highly controlled by the eukaryote nucleus that they are functionally organelles.

Now that I did not know. I thought the mitochondria were completely independent, which was confusing me a little. I am totally failing my A level. Not to worry....

 

[Halcyon]

Now that I did not know. I thought the mitochondria were completely independent, which was confusing me a little. I am totally failing my A level. Not to worry....

Relax, from what i remember you don't need to know too much for A-level. This is more first year university stuff we're talking about.

 

[Gentoo]

Also, and this is just me speculating, during the early stages of embryonic development when cells are specialising, cells may split unsymmetrically - possibly more mitochondria are moved to one half of the mother cell via the cytoskeleton prior to mitosis. But i'm just postulating here, don't take that as fact or anything.

I think you were referring to non-disjunction, where the number of chromosomes is unequal in terms of meiotic division, it's how Down's Syndrome (three number 15 chromosomes rather than 2). But I haven't heard of it happening with other organelles, I also haven't taken cell biology though.

 

[Halcyon]

I think you were referring to non-disjunction, where the number of chromosomes is unequal in terms of meiotic division, it's how Down's Syndrome (three number 15 chromosomes rather than 2). But I haven't heard of it happening with other organelles, I also haven't taken cell biology though.

No, its been a while since i finished my degree so i'm a bit fuzzy on the processes. I know that during either cell division the organelles are usually split equally. I'm just guessing that during cell differenciation that perhaps organelles may be split unevenly, i didn't do too much on embryonic development at uni, mostly concentrated on population dynamics and ecology, so this is pure speculation on my part.

 

[Valjean]

Clearly the mitochondrial assembly programme has insinuated itself into our own DNA. There's nothing odd in this -- viruses do it all the time.
Mitochondria are present and functioning in the tiniest foetus. I doubt the foetus picked them up externally. No-one's ever found free ranging, independant Mitochondria anywhere.

 

[Halcyon]

Clearly the mitochondrial assembly programme has insinuated itself into our own DNA. There's nothing odd in this -- viruses do it all the time.
Mitochondria are present and functioning in the tiniest foetus. I doubt the foetus picked them up externally. No-one's ever found free ranging, independant Mitochondria anywhere.

Although they have found a similar bacterium somewhere, if only i hadn't recycled my uni notes .

Also, interesting fact of the day, all our mitochondria are inherited from our mothers - the reason is because a sperm cell is quite weird as cells go.
The head is pretty much just a nucleus surrounded by a membrane, the tail is packed with mitochondria which supply the ATP necessary for the little dudes to do all that swimming. At fertilisation the tail breaks off, only the head enters the egg. So poor daddy doesn't get to pass on his endosymbiotes.

 

[Rough_ER]

Aren't all our other organelles from our mother too? That's what I thought, as a sperm is just too small to house things like ER and Golge etc. Is a sperms tail anything like a flagellum by the way? I have been wondering.

 

[Halcyon]

Aren't all our other organelles from our mother too? That's what I thought, as a sperm is just too small to house things like ER and Golge etc. Is a sperms tail anything like a flagellum by the way? I have been wondering.

There will be some purely maternal organelles present in the egg, but when the cell splits new organelles will need to be made, and these are formed from the newly combined DNA.
It's only the mitochondria, which still have a small part of their own coding DNA, that cannot be recreated from scratch using nuclear DNA.