Ars Technica
A short but interesting article on an apparent observed endosymbiosis event.
Evolution caught in the act?
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SeeingRed
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Evolution caught in the act?
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Fucksake, post the damn article!
Evolution caught in the act?
One of the rarest of evolutionary events appears to have been endosymbiosis, a process in which two formerly independent cells began a symbiotic relationship after having one swallow the other with the intent of making it a meal. In the distant past, this process provided eukaryotes with two of their most important organelles: mitochondria, which produces much of the cell's ATP, and chloroplasts, which allow plants and algae to capture light energy. These events, however, appear to have occurred over a billion years ago. These organelles maintain a minimal genome, but much of their original genetic material has been deleted or transferred to the host organism's nucleus, frustrating attempts to fully understand how the transformation to endosymbiosis occurs at the genetic level.
But eukaryotes haven't stopped trying to eat other cells in the intervening billion years, and new data now suggests that a species of amoeba has recently acquired its own version of the chloroplast, along with its light harvesting benefits. The amoeba, Paulinella chromatophora, and its endosymbiont, termed a cyanelle, have been suspected of being unusual for roughly a century. Its closest relatives can't do photosynthesis, and make their living by eating cyanobacteria, the modern version of the organism that was turned into a chloroplast in the past. The cyanelle looks externally identical to a bacteria, but can no longer live outside of the amoeba. The two cells have become somewhat integrated, as the duplication of the cyanelle is coordinated with cell division, and Paulinella appears to have given up on attempts to digest it.
If this is a more recent endosymbiotic event than the ones in eukaryotes' distant past, the obvious question is how recent? The new report describes the sequencing of portions of the cyanelle's genome, which revealed that it is essentially still a bacteria. All the genes that have been sent to the nucleus by chloroplasts are still present, as are many that have been deleted entirely (such as those for fixing nitrogen). Although only small sections of the genome have been examined, the clear relationship with existing cyanobacteria indicates that the endosymbiosis event was very, very recent. The data suggest that a full sequencing of the genomes of both halves of this relationship should be very revealing, as they may indicate how long ago the endosymbiosis took place, as well as the minimal changes necessary for the commencement of this sort of relationship.
Unfortunately, that data may be hard to come by, as nobody's figured out how to grow Paulinella in the lab, meaning there are constant problems with contaminated materials and impure samples. That's also the case with another likely endosymbiotic species that the authors of this paper cite. In that case, a protist carries a single algal cell, which only one of its offspring inherits following cell division. The offspring without it develops a feeding apparatus, hunts down, and eventually swallows another algal cell, starting the process over again. This indicates that it's probably at an even earlier stage of the process than Paulinella. But the presence of two cases where endosymbiosis appears to be at a preliminary stage suggests that the process may be far more amenable to study than I would have imagined. Assuming we can actually get the things to grow in the lab, of course.
Evolution caught in the act?
One of the rarest of evolutionary events appears to have been endosymbiosis, a process in which two formerly independent cells began a symbiotic relationship after having one swallow the other with the intent of making it a meal. In the distant past, this process provided eukaryotes with two of their most important organelles: mitochondria, which produces much of the cell's ATP, and chloroplasts, which allow plants and algae to capture light energy. These events, however, appear to have occurred over a billion years ago. These organelles maintain a minimal genome, but much of their original genetic material has been deleted or transferred to the host organism's nucleus, frustrating attempts to fully understand how the transformation to endosymbiosis occurs at the genetic level.
But eukaryotes haven't stopped trying to eat other cells in the intervening billion years, and new data now suggests that a species of amoeba has recently acquired its own version of the chloroplast, along with its light harvesting benefits. The amoeba, Paulinella chromatophora, and its endosymbiont, termed a cyanelle, have been suspected of being unusual for roughly a century. Its closest relatives can't do photosynthesis, and make their living by eating cyanobacteria, the modern version of the organism that was turned into a chloroplast in the past. The cyanelle looks externally identical to a bacteria, but can no longer live outside of the amoeba. The two cells have become somewhat integrated, as the duplication of the cyanelle is coordinated with cell division, and Paulinella appears to have given up on attempts to digest it.
If this is a more recent endosymbiotic event than the ones in eukaryotes' distant past, the obvious question is how recent? The new report describes the sequencing of portions of the cyanelle's genome, which revealed that it is essentially still a bacteria. All the genes that have been sent to the nucleus by chloroplasts are still present, as are many that have been deleted entirely (such as those for fixing nitrogen). Although only small sections of the genome have been examined, the clear relationship with existing cyanobacteria indicates that the endosymbiosis event was very, very recent. The data suggest that a full sequencing of the genomes of both halves of this relationship should be very revealing, as they may indicate how long ago the endosymbiosis took place, as well as the minimal changes necessary for the commencement of this sort of relationship.
Unfortunately, that data may be hard to come by, as nobody's figured out how to grow Paulinella in the lab, meaning there are constant problems with contaminated materials and impure samples. That's also the case with another likely endosymbiotic species that the authors of this paper cite. In that case, a protist carries a single algal cell, which only one of its offspring inherits following cell division. The offspring without it develops a feeding apparatus, hunts down, and eventually swallows another algal cell, starting the process over again. This indicates that it's probably at an even earlier stage of the process than Paulinella. But the presence of two cases where endosymbiosis appears to be at a preliminary stage suggests that the process may be far more amenable to study than I would have imagined. Assuming we can actually get the things to grow in the lab, of course.
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wolveraptor
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Goddamn, it doesn't say what species the endosymbiont is derived from.
Nevertheless, this:
Nevertheless, this:
was fucking cool.That's also the case with another likely endosymbiotic species that the authors of this paper cite. In that case, a protist carries a single algal cell, which only one of its offspring inherits following cell division. The offspring without it develops a feeding apparatus, hunts down, and eventually swallows another algal cell, starting the process over again.
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Cyanobacteria is a huge fucking Order(Is it order? So many levels to organization.) He was hoping for a species name with the possibility of a genus, which would have been sweet because you can then find that cyanobacteria in the wild and potentially try to set up a lab experiment to duplicate this.Xeriar wrote:Cyanobacteria, or something related to them, apparently.wolveraptor wrote:Goddamn, it doesn't say what species the endosymbiont is derived from.
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