DrmDoc Posted February 27, 2022 Posted February 27, 2022 "Scientists discovered an absolutely massive bacterium that can be seen without the aid of a microscope and lurks among the mangroves of Grande-Terre in the Caribbean, Science magazine reported." That comment is from a Live Science article about a new bacterium, 2 centimeters long, that was recently discovered in the Caribbean. Enjoy! 2
Area54 Posted February 27, 2022 Posted February 27, 2022 I have noticed that a high proportion of posts and threads in the Science forum are only marginally about science. Members seem to take more pleasure out of arguing politics, or maybe its just about arguing. At any rate, I've resolved to upvote every thread OP that is science oriented and you are the first recipient of this decision.:) The post is independently worthy of an upvote anyway, since it is quite fascinating. The size alone is remarkable, but the insights into the evolution of eukaryotes provided by its "membranous pouch" containng the organisms DNA are intriguing. I look forward to more revelations following further study. 1
Peterkin Posted February 27, 2022 Posted February 27, 2022 There is a little more in the Science article, linked to this one. No enlarged microscopy pictures, unfortunately, so we have to rely on their description of the insides. But, wow! what a stash of DNA!
Genady Posted February 27, 2022 Posted February 27, 2022 What do they mean when they call an extant organism a "missing link"?
Area54 Posted February 27, 2022 Posted February 27, 2022 3 minutes ago, Genady said: What do they mean when they call an extant organism a "missing link"? It contains features that link seperate species, or families, or - as in this case - domains. Bacteria don't have cell nuclei. Their DNA is distrbuted throughout the cell. This example has the DNA restricted to a membrane encase pouch. That is plausibly a step through which life passed in moving from prokaryotes (no nuclei) to eukaryotes (nuclei). i.e. a missing link. 1
Genady Posted February 27, 2022 Posted February 27, 2022 3 minutes ago, Area54 said: It contains features that link seperate species, or families, or - as in this case - domains. Bacteria don't have cell nuclei. Their DNA is distrbuted throughout the cell. This example has the DNA restricted to a membrane encase pouch. That is plausibly a step through which life passed in moving from prokaryotes (no nuclei) to eukaryotes (nuclei). i.e. a missing link. They have had the same billions of years to evolve to what they are today as the eukaryotes. Isn't it just another line of evolution from whatever common ancestor we share? The bacterial DNA is not actually distributed throughout the cell. Their DNA is arranged in chromosomes, which differ from eukaryotic chromosomes in being circular rather than linear. Curious, what is a shape of chromosomes of these new organisms? BTW, the article says that their ribosomes are in the same pouch, with the DNA. This is crucially different from the eukaryotes whose ribosomes are outside the nuclei. This pouch doesn't resemble the eukaryotic nucleus functionally. Looks more like a superficial resemblance to me.
Peterkin Posted February 27, 2022 Posted February 27, 2022 14 minutes ago, Genady said: They have had the same billions of years to evolve to what they are today as the eukaryotes. Isn't it just another line of evolution from whatever common ancestor we share? Of course. One branch went on to branch and branch and branch, until it became all kinds of organisms, many of which have since become extinct. This branch remained unchanged or changed very little, (like ants and hydras) I suppose because they found an ecological niche that still works for them. The "missing link" does not refer its evolution but to our knowledge. 20 minutes ago, Genady said: Curious, what is a shape of chromosomes of these new organisms? I would very much like to see a magnified cross section. Haven't had time to search.
Area54 Posted February 27, 2022 Posted February 27, 2022 20 minutes ago, Genady said: They have had the same billions of years to evolve to what they are today as the eukaryotes. Isn't it just another line of evolution from whatever common ancestor we share? Yes, but I don't see your point. This does not contradict my observations. 22 minutes ago, Genady said: BTW, the article says that their ribosomes are in the same pouch, with the DNA. This is crucially different from the eukaryotes whose ribosomes are outside the nuclei. This pouch doesn't resemble the eukaryotic nucleus functionally. Looks more like a superficial resemblance to me. Again, I am not sure what you are driving at. I've offered an explanation of why this was described as a missing link - a shorthand way of noting an interesting, plausible step between prokaryote and eularyote. Researchers have hypothesised the separation of DNA into a separate 'compartment'. Now we have a a living instance of an organism with this feature. It is incidental that the ribosomes are also in the pouch.
Genady Posted February 27, 2022 Posted February 27, 2022 4 minutes ago, Peterkin said: Of course. One branch went on to branch and branch and branch, until it became all kinds of organisms, many of which have since become extinct. This branch remained unchanged or changed very little, (like ants and hydras) I suppose because they found an ecological niche that still works for them. The "missing link" does not refer its evolution but to our knowledge. I would very much like to see a magnified cross section. Haven't had time to search. We don't even know that it remained unchanged or changed very little. Maybe they evolved relatively recently.
Peterkin Posted February 27, 2022 Posted February 27, 2022 (edited) 56 minutes ago, Genady said: We don't even know that it remained unchanged or changed very little. True. That was my assumption, from the little bit I've read on it. Of course, it's still a descendant of our common family tree, but on a twig very, very far from the one on which we're hanging. 56 minutes ago, Genady said: Maybe they evolved relatively recently. Okay. When? From what? There has to be some observed data to prompt a hypothesis, and I'm not aware of one that posits a recent origin for this species. That doesn't mean it's wrong, just that I don't know enough (given I only learned of its existence this afternoon) about T. magnifica to speculate. Edited February 27, 2022 by Peterkin
Genady Posted February 27, 2022 Posted February 27, 2022 2 minutes ago, Peterkin said: True. That was my assumption, from the little bit I've read on it. Of course, it's still a descendant of our common family tree, but on a twig very, very far from the one on which we're hanging. Okay. When? From what? There has to be some observed data to prompt a hypothesis, and I'm not aware of one that posits a recent origin for this species. That doesn't mean it's wrong, just that I don't enough about T. magnifica to speculate. Yes, not enough data. The only knowledge is that they evolved some time during the last 3-4 billion years. At any time during this window. They live on mangroves. How long do mangroves exist? Not very long.
Peterkin Posted February 27, 2022 Posted February 27, 2022 11 minutes ago, Genady said: How long do mangroves exist? Not very long. Depends what you consider 'very long'. Quote The oldest known fossils of mangrove palm date to 75 million years ago - wiki And just because they live in conjunction with mangroves now, we can't assume that they have not changed habitats and food sources sometime, or many times, during their history. Let's give the researchers a couple of days to study on it.
Genady Posted February 27, 2022 Posted February 27, 2022 Yes, 75 million years I consider not long at all on the 3-4 billion years scale. Mostly, after the dinosaurs. Of course they have changed their habitat many times. This is evolution. The unknown we are talking about is, when during this evolution they evolved this peculiar compartmentation.
Peterkin Posted February 27, 2022 Posted February 27, 2022 23 minutes ago, Genady said: Yes, 75 million years I consider not long at all on the 3-4 billion years scale. How about on the bacterial scale? Mangrove trees live over 100 years each, while bacteria live o more than a day. The turnover, and thus mutation opportunity and thus evolution, is considerably faster on that scale.
Genady Posted February 27, 2022 Posted February 27, 2022 1 minute ago, Peterkin said: How about on the bacterial scale? Mangrove trees live over 100 years each, while bacteria live o more than a day. The turnover, and thus mutation opportunity and thus evolution, is considerably faster on that scale. I wondered how fast this bacterium reproduces considering its size. But anyway, their evolution occurring faster they could evolve this feature really recently. How about in the last million years, for example?
Peterkin Posted February 27, 2022 Posted February 27, 2022 11 minutes ago, Genady said: they could evolve this feature really recently. How about in the last million years, for example? Why not? I hope somebody who actually knows tells us pretty soon.
Genady Posted February 27, 2022 Posted February 27, 2022 4 minutes ago, Peterkin said: Why not? I hope somebody who actually knows tells us pretty soon. Don't hold your breath.
CharonY Posted February 27, 2022 Posted February 27, 2022 1 hour ago, Genady said: Yes, not enough data. The only knowledge is that they evolved some time during the last 3-4 billion years. At any time during this window. They live on mangroves. How long do mangroves exist? Not very long. Thimargarita have been found in various habitats and are not unique to mangroves. IIRC they were originally isolated from ocean sediments. They have a predominantly anaerobic metabolism using among others hydrogen sulfide as electron donor and nitrate as acceptor. The ability to gain that size is based on at least two important factors. First, they are sessile, so mobility is not an issue as for many other bacteria. The second is that are able to store nutrients which allows them to survive nutrient fluctuations, despite being sessile.
Genady Posted February 27, 2022 Posted February 27, 2022 2 minutes ago, CharonY said: Thimargarita have been found in various habitats and are not unique to mangroves. IIRC they were originally isolated from ocean sediments. They have a predominantly anaerobic metabolism using among others hydrogen sulfide as electron donor and nitrate as acceptor. The ability to gain that size is based on at least two important factors. First, they are sessile, so mobility is not an issue as for many other bacteria. The second is that are able to store nutrients which allows them to survive nutrient fluctuations, despite being sessile. Yes, however until this recent discovery they all were less than 1 mm in size and didn't have a DNA pouch. The new one is almost 1 cm long, has DNA pouch, and has been discovered in some Caribbean mangroves.
CharonY Posted February 28, 2022 Posted February 28, 2022 13 minutes ago, Genady said: Yes, however until this recent discovery they all were less than 1 mm in size and didn't have a DNA pouch. The new one is almost 1 cm long, has DNA pouch, and has been discovered in some Caribbean mangroves. I would have to look at the lit again, but I am fairly certain that Thimargarita most species had elaborate internal membrane structures which, including vacuole-like structures. I am fairly certain that the DNA in the earlier detected species was also well localized, and something similar has been observed in another giant bacterium (Epulopiscium ep.). It is quite likely that membrane structures are involved, but they might be difficult to properly visualize (as e.g. TEM or other techniques often are do not preserve those structures well). It is therefore possible that either the newly developed species is more compartmentalized or that the compartments are easier visualized as they are larger. It should also be noted that it is sometime reported that DNA in bacteria are free-floating. This is actually not the case as high-resolution analyses (as well as some indirect evidence) does suggest that bacteria organize their internal organelles to quite some degree and are bound to the membrane in a specific way. This is more obvious in large, elongated cells, but is likely somewhat universal, if underappreciated. Thus larger bacteria with internal membrane segmentation to that degree are certainly rare, but we see the basic principles that might be related to that level of organization in most bacteria. I have to say that sub-cellular anatomy might be one of my weaker areas when it comes to bacteria as I have not been doing these types of projects for quite a long time now, and I am not sure where the current literature is at.
Genady Posted February 28, 2022 Posted February 28, 2022 9 minutes ago, CharonY said: I would have to look at the lit again, but I am fairly certain that Thimargarita most species had elaborate internal membrane structures which, including vacuole-like structures. I am fairly certain that the DNA in the earlier detected species was also well localized, and something similar has been observed in another giant bacterium (Epulopiscium ep.). It is quite likely that membrane structures are involved, but they might be difficult to properly visualize (as e.g. TEM or other techniques often are do not preserve those structures well). It is therefore possible that either the newly developed species is more compartmentalized or that the compartments are easier visualized as they are larger. It should also be noted that it is sometime reported that DNA in bacteria are free-floating. This is actually not the case as high-resolution analyses (as well as some indirect evidence) does suggest that bacteria organize their internal organelles to quite some degree and are bound to the membrane in a specific way. This is more obvious in large, elongated cells, but is likely somewhat universal, if underappreciated. Thus larger bacteria with internal membrane segmentation to that degree are certainly rare, but we see the basic principles that might be related to that level of organization in most bacteria. I have to say that sub-cellular anatomy might be one of my weaker areas when it comes to bacteria as I have not been doing these types of projects for quite a long time now, and I am not sure where the current literature is at. Thank you. I'm very glad to hear this, because I don't like the sensationalistic hint in the original report about a possible discovery of a "missing link" between prokaryotes and eukaryotes. Although, I have to clarify, this "missing link" speculation appears only in the pop sci report, NOT in the primary report in bioarxiv.
Area54 Posted March 3, 2022 Posted March 3, 2022 On 2/28/2022 at 12:31 AM, Genady said: Thank you. I'm very glad to hear this, because I don't like the sensationalistic hint in the original report about a possible discovery of a "missing link" between prokaryotes and eukaryotes. Although, I have to clarify, this "missing link" speculation appears only in the pop sci report, NOT in the primary report in bioarxiv. Am I correct in understanding that you see nothing in this research that can inform our understanding of the emergence of eukaryotic features from prokaryotic anncestors? If not, why the dislike. If so, how odd.
Genady Posted March 3, 2022 Posted March 3, 2022 1 hour ago, Area54 said: Am I correct in understanding that you see nothing in this research that can inform our understanding of the emergence of eukaryotic features from prokaryotic anncestors? If not, why the dislike. If so, how odd. I don't see in this research suggestion of a new hypothesis about the emergence of eukaryotic features from prokaryotic ancestors, neither a new support for any existing hypothesis. I see a way of storing DNA in gigantic bacteria.
Area54 Posted March 5, 2022 Posted March 5, 2022 On 3/3/2022 at 9:08 PM, Genady said: I don't see in this research suggestion of a new hypothesis about the emergence of eukaryotic features from prokaryotic ancestors, neither a new support for any existing hypothesis. I see a way of storing DNA in gigantic bacteria. That is an interesting observation, but it fails to answer my question. I wasn't asking about any novel hypothesis. All can infer from your post is that you do not think this research adds anything to our understanding of eukaryote evolution. From my pesrpective that seems a fauly view, but you are, of course, entitled to hold it.
Genady Posted March 5, 2022 Posted March 5, 2022 1 hour ago, Area54 said: That is an interesting observation, but it fails to answer my question. I wasn't asking about any novel hypothesis. All can infer from your post is that you do not think this research adds anything to our understanding of eukaryote evolution. From my pesrpective that seems a fauly view, but you are, of course, entitled to hold it. I'd like to learn what and how this research adds to our understanding of eukaryote evolution.
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