Talk:Endosymbiont
From Academic Kids
I'm interested about these Eucaryota-Endosymbionts. Could you elaborate about them ?
- Some examples.
- Are they simplified in some way ?
- Is their replication process different from free Eucaryotas'. ?
- Do they have mitochondrions ?
Are there any Endosymbionts living in Procaryota ?
I can tell you what I know. First note, though, that mitochondria and chloroplasts are unusual among prokaryotic endosymbionts for being so specialized - most are simply bacteria that can live inside or outside the host. The only analagous eukaryotic endosymbionts I can think of are the chloroplasts of the cryptomonads, which actually contain a reduced nucleus (nucleomorph) in addition to the green prokaryote proper.
For single-celled hosts, zooxanthellae also come to mind. These are tiny green dinoflagellates that live within the frothy outer parts of some amoeboids, and I think in some anenomes. In this case the cells stay in a palmelloid stage - that is they do not have their flagella or their shells - but are otherwise fully intact, and will regenerate if removed from the host. The amoeba I gather receives some energy from them. A similar thing happens with the algae found inside lichens.
Animals have a whole host of bacteria and protozoa in their gut. Of special note here I suppose are the protists that live in the gut of termites and digest cellulose for them. These aren't reduced in any way except possibly in that they lack mitochondria, but it is generally supposed that they branched off before mitochondria were developed, and they contain bacterial endosymbionts instead, which do the digesting for them. And remember that symbionts don't have to be helpful, so trypanosomes and sporozoans as well as larger things like tapeworms and roundworms would count as endosymbionts as well.
I don't think any prokaryotes have endosymbionts, and they certainly don't have any eukaryotic ones - the difference in size of the cells is simply too great. I suppose one might consider viri something of this sort, but generally the requirement is that endosymbionts have to be removeable from the host in some way. Hmm, thinking about it this may invalidate some of the examples above. Well, I hope that was some help, or at least interesting. --Josh Grosse :)
Hm. Shouldn't this and endosymbiosis be merged? If a merge is in order then all the text should be at the page which describes the phenomenon (sic endosymbiosis). --mav
I've merged endosymbiosis and endosymbiont, somewhat arbitrarily deciding that endosymbiont will be the main page, since I guess I've seen this form of the word used more. Few notes:
- I removed the reference to cellulose-digesting protozoa, since it was kind of vague, and I don't myself know any more info.
- I put some specific info on nitrogen-fixing bacteria, but not much more info.
- The page now has an admittedly overblown references section, which is mostly from the primary literature. It'd be great if someone could track down the seminal paper on the endosymbiont theory of mitochondria and chloroplasts, or find some more general-reader references to supplement the academic ones
- Obviously I know more about bacterial endosymbionts in insects; someone who knows the endosymbiont theory of organelles is enthusiastically encouraged to flesh things out - in particular, I think there's more support for the theory than what I put in.
I disagree with the page title since it mixes the two entities in the wrong way. First and foremost endosymbiosis is an evolutionary process so that explanation should be at endosymbiosis. A discussion about particular ones should be at endosymbiont. See how parasitism and parasite are set-up. --mav
Hmm. I think I'm approaching this from the side of endosymbionts in insects & then I got into the Endosymbiont Theory of mitochondria & chloroplasts, while it seems like you & others got into this from the mito&chloro side. I thought that "endosymbiosis" merely refers to a relationship between an endosymbiont and a host, and doesn't necessarily have anything to do with evolution. I think this usage is common in the literature, and it's supported by analogy with symbiosis, which just refers to a relationship between a symbiont and host. Looking through some google hits ( http://www.google.com/search?q=endosymbiosis ) and the literature I read earlier seems to support this as the primary usage. However, I see now that many people do use endosymbiosis as an evolutionary process that starts with an endosymbiosis, as you suggest, so that usage should probably be reflected in the article.
As for the splitting, I personally feel that there's not really much point in splitting things into 2 articles, and the distinction between the topics may not be clear to the reader. I realize this is pretty subjective, but in reading the parasitism article, it's not clear that the parasite link will give me examples of parasitism. Perhaps a "parasitism, examples of" link would be more straightforward, although both articles are short enough that I think the examples could be folded into one article.
After some further thinking, perhaps a solution is to put the mito/chloro stuff under the heading "The Endosymbiont Theory", which I've seen used for Margulis's theory (or maybe another term). Under this scheme, I'd propose something like this:
- The "endosymbiont" article defines endosymbiont AND endosymbiosis (in the non-evolution definition), gives the stuff about endosymbiosis in insects, and briefly makes a reference to the Endosymbiont Theory page.
- The "Endosymbiont Theory" article briefly makes reference to the endosymbiont article, and then proposes the theory that mito/chloro arose by an ancient endosymbiosis. This article could also optionally discuss endosymbiosis as a evolutionary process in general (see the article on evolution of flagella, though, which I think might have some overlapping info)
This would separate the notions of endosymbiosis as a condition that exists currently in nature (e.g. in insects), vs. endosymbiosis as a proposed mechanism of evolution. I'm guessing that you were concerned that I was conflating endosymbiosis as current fact vs. endosymbiosis as evolutionary process, and we just happened to have different definitions of the word "endosymbiosis"?
What do you think?
This may be a difference in usage between sub-disciplines. My training has focused on cellular and micro-biology with an emphasis in evolutionary change and I think you are coming from a different direction that focuses on organisms as they are now. Endosymbiosis, for me, has only been used in reference to the theory about how eukaryotic cells evolved from prokaryotic-like predecessors. When I saw your great additions to this (the endosymbiont) article I at first thought that my understanding of the concept was limited by my specific concentration within biology. I now think that I was in error and the merge has resulted in a greater amount of confusion since the word endosymbiont is used in two, admittedly closely related, ways;
- the ancient prokaryotes that lived within the progenitor eukaryotic cells were endosymbionts.
- there are currently other cells that live within cells that are called endosymbionts.
But the normal usage of the term endosymbiosis that I am aware of refers to the evolutionary process that resulted in the development of eukaryotic cells. So this needs a separate article that introduces endosymbionts. Oh, and it would be the endosymbiotic theory and not endosymbiont theory since it is a theory about a process and not about the result of that process.
So we might have an article about endosymbiosis that concentrates on the general usage of the term (your usage and mine). This will be a page similar to virus (which is just a glorified disambiguation page turned into an actual article). That article introduces the endosymbiont article (which concentrates on current endosymbionts but mentions the ancient ones) and also the endosymbiotic theory that only talks about Lynn Margulis' etc theory about eukaryotic evolution. You can probably guess that I am a divider and not a lumper. :-) --mav
I actually think that makes sense. A PubMed search (for endosymbio* theory at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed) agrees that it's endosymbiotic theory (although in my defence, a few articles do use endosymbiont theory :-) So, what it sounds like is
- endosymbiosis: the glorified disambiguation page
- endosymbiont: defines endosymbiont and gives current examples. mentions the endosymbiotic theory just to link to it. mentions the different uses of endosymbiosis, linking to the disambiguation page.
- endosymbiotic theory: discusses Margulis's theory, possibly moving some stuff currently in endosymbiont and evolution of flagella there. Defines endosymbiont and refers to the endosymbiont article. mentions the different uses of endosymbiosis, linking to the disambiguation page.
(note that I'm implicitly suggesting the endosymbiont and endosymbiotic theory pages do a bit of disambiguation themselves in referring to each other, since the concepts are closely related)
I'm going to have only sporadic internet access for the winter break, so if you'd like to try some changes, that'd be cool. We seem to be more or less on the same page about this, so I don't foresee any major flaming afterwards :-P
- Excellent! I'll see if I can get around to this after Christmass. --mav
I did the changes myself. (I figured you're okay with this.) As always, feel free to edit things, or comment -- I don't claim I made the changes perfectly :-). We now have:
BTW, I also criticized the new Endosymbiotic Hypothesis page (conceding that I'm responsible for much of the content...) You seem to know a lot about evolution, so I'd like to draw you attention to the article's talk page, where I outlined what I think should be done with it.
The organization looks good to me. Sorry I didn't do this as promised but updating these day and year pages takes several hours each day. I'll take a look at the talk page and comment. --mav
Sounds good. --User:zashaw
Question
Don't most (all?) higher organisms have organizisms such as bacteria that live inside of them that could be considered endosymbionts? Gut bacteria, etc. I can't recall the article, but I read in a Wikipedia article that rodents of some sort were bred entirely sterile and ended up dying of very odd disorders, the hypothesis being they (and by extension humans) need the bacteria, etc to survive. The article seems to only mention non vertebrate examples. Thanks - Taxman 03:05, May 1, 2005 (UTC)
