Does scientific research back the claims made in this article? Samiya Amoebic Morality <http://www.damninteresting.com/amoebic-morality/ >
[image: Dictyostelium discoideum composite photo, Copyright © M.J. Grimson & R.L. Blanton; Biological Sciences Electron Microscopy Laboratory, Texas Tech University] Dictyostelium discoideum composite photo, Copyright © M.J. Grimson & R.L. Blanton; Biological Sciences Electron Microscopy Laboratory, Texas Tech University Once food had been plentiful, but no longer. In the early days of the colony, the amoebas had feasted on a rich supply of bacteria. But as the generations passed and the population swelled, they had hunted out their food supply. Now starvation threatens. Their home-- a scrap of deer dung which once provided all their needs-- has become a trap which they must escape if they are to survive. At last, one amoeba sends out a cry for help. The starving amoeba begins to emit a chemical signal in the form of *cyclic adenosine monophosphate*, or cAMP. Nearby individuals sprout new pseudopods and crawl toward the source. They also begin to give off cAMP themselves, amplifying the call until the signal spreads to the far reaches of the colony. Amoebas cannot concurrently detect and produce cAMP, so they alternate, and the cells trace out intricate spiral patterns as they surge forward in waves. The amoebas pile on top of one another in growing numbers until so many of them have joined the heap that this pile of microscopic single-celled organisms becomes visible to the naked eye. At first their behavior might seem odd; to gather together in the face of starvation surely ought to end in cannibalism or death. Not so, for they are capable of an extraordinary and rare transformation. The amoebas set aside their lives as individuals and join ranks to form a new multicellular entity. Not all the amoebas will survive this cooperative venture, however. Some will sacrifice themselves to help the rest find a new life elsewhere. These astonishing creatures are *Dictyostelium discoideum*, and they are a member of the slime mold family. They are also known as social amoebas. Aside from the novelty value of an organism that alternates between unicellular and multicellular existence, D. discoideum is highly useful in several areas of research. Among other things, this organism offers a stellar opportunity to study cell communication, cell differentiation, and the evolution of altruism. In response to the cAMP distress call, up to one hundred thousand of the amoebas assemble. They first form a tower, which eventually topples over into an oblong blob about two millimeters long. The identical amoebas within this *pseudoplasmodium*-- or slug-- begin to differentiate and take on specialized roles. The slug begins to seek out light, leaving a slimy trail behind. Some of the amoebas take on the difficult role of sentinel, or immune-like functions. They circulate through the slug, hunting for pathogens. If they find any, they will engulf them in a process similar to the feeding behavior they once displayed when in solitary form. The pseudoplasmodium periodically sloughs off the sentinels-- and any pathogens they have engulfed-- and abandons them in the trail of slime. More cells will then be tapped to fill their place. [image: Dictyostelium discoideum slug] Dictyostelium discoideum slug Once the slug finds a suitably sunny location, the unlucky cells at the "head" of the slug form a stalk for the others to climb. These cells--which make up roughly a fifth of the total population--will sacrifice themselves in order to provide a path up for their comrades. The remaining cells then climb the stalk and collect on its tip, eventually resulting in a structure resembling a ping-pong ball balanced on top of a floppy wire. This formation is known as a "fruiting body." They then form spores, which are carried away by wind or passing animals or insects. Once carried to a suitable location, the amoebas emerge from spore form and begin the cycle again. So long as all the amoebas which make up the slug are related, this impressive display of self-sacrifice on the part of the stalk cells makes sense. Though they will perish in the act of creating the stalk, they will pass along their genetic legacy via their kin. In fact, when the amoebas reproduce by division, they create an ever-increasing pool of genetically identical clones. These clones suffer no genetic cost at all from sacrificing their lives for each other. More familiar multicellular organisms pool resources in a similar way. For example, in a human being, a liver cell fills a very different role from a lung or skin cell, but all of them harbor the same chromosomes. The result is that the liver doesn't need to compete with the lungs concerning reproduction. So long as the germ cells get lucky, all of the cells can be (metaphorically) content knowing they will pass on their genetic legacy. However, when the cAMP call goes out, it isn't only related amoebas that answer it. Those of differing strains will come together to form a single slug. If one strain could figure out a way to duck out of stalk and sentinel duty, it would be expected to reproduce faster than its nobler compatriots. As is true with all organisms, some will evolve in such a way that they can-- and will-- benefit from the colony's resources without contributing anything back. In theory, such "leeches" could potentially have a survival and reproductive advantage, thereby undermining the cooperative Dictyostelid lifestyle. Such cheating does take place, but nonetheless D. discoideum has been around for millions of years with no signs of imminent extinction. Thus the mechanisms for keeping cheating under control must be effective. For one thing, the amoebas prefer to unite with kin. The amoebas are able to recognize each other through molecular markers. They mingle with other strains only when populations are low. At such times, the ability to form a larger slug outweighs the risk of cooperating with strangers. [image: A typical amoeba] A typical amoeba In addition, evidence suggests that some social amoebas have evolved to link reproductive genes with altruistic ones. In the case of D. discoideum, researchers created a mutant strain of cells which are "deaf" to the chemical signal to become a self-sacrificing stalk cell. They then watched to see if these cells would gain a reproductive advantage. Just the opposite took place. The "cheater" mutant cells did not join in stalk formation, yet they rarely made it up the stalk to become spores, and therefore they died out. The traits of self-sacrifice and reproduction had become genetically entangled, it seems, allowing only the altruistic amoebas to produce offspring. Finally, opportunities for cheating simply aren't very common. In the wild, these creatures spend much of their lives reproducing via division, and surrounding themselves with identical copies. Outside of laboratory experiments, cases where social amoebas run across strangers to exploit are rare. Cheater genes peter out once the cheaters run out of nobler amoebas to sponge off of. When exploiting one's clone mates, greed doesn't pay. In addition to studies of altruism, study of D. discoideum is shedding light on how cells communicate. D. discoideum uses many of the same signaling processes found in all multicellular creatures. But unlike fish or frogs, D. discoideum can be frozen, thawed, grown by the millions in a matter of days, and stored away for years if need be. A website called DictyBase offers an impressive list of breakthroughs which can be credited to the social amoeba. The consistency with which these amoebas act in the common good might inspire admiration in many. Yet a more cynical observer might point out that the amoebas are moved not by love of family and friends, nor by moral scruples, but by the cold mechanics of natural selection. Amoebas behave altruistically only because natural selection has led to a stable state in which self-sacrifice is the best way for them to pass on their genes. But the end result is the same, regardless of the natural forces that have shaped it. Altruism triumphs, and through their mutual selflessness the amoebas arrive at a new patch of bacteria-laden dung to call home. Written by Carol Otte <http://www.damninteresting.com/?page_id=886>, posted on 09 October 2007. Carol is a contributing editor for DamnInteresting.com. On Thu, Apr 24, 2014 at 6:54 PM, Bruno Marchal <[email protected]> wrote: > > On 24 Apr 2014, at 12:26, Richard Ruquist wrote: > > Microbes provide insights into evolution of human language > April 23rd, 2014 in Biology / Cell & Microbiology > > Gram-stained Pseudomonas aeruginosa bacteria (pink-red rods). Credit: > GFDL, CC-by-sa > > Big brains do not explain why only humans use sophisticated language, > according to researchers who have discovered that even a species of pond > life communicates by similar methods. > > Dr Thom Scott-Phillips of Durham University led research into Pseudomonas > aeruginosa, a type of bacteria common in water and soil, which showed that > they communicated in a way that was previously thought to be unique to > humans and perhaps some other primates. > > The bacteria used combinatorial communication, in which two signals are > used together to achieve an effect that is different to the sum of the > effects of the component parts. This is common in human language. For > example, when we hear 'boathouse', we do not think of boats and houses > independently, but of something different - a boathouse. > > This type of communication had never been observed in species other than > humans and some other primates, until colonies of Pseudomonas aeruginosa > were shown to be using the same technique - not, of course, with spoken > words but with chemical messengers sent to each other that signalled when > to produce certain proteins necessary for the bacteria's survival. > > By blocking one signal, then the other, the researchers showed if both > signals were sent separately, the effect on protein production was > different from both signals being sent together. > > Dr Scott-Phillips, a research fellow in evolutionary anthropology at > Durham University, conducted the research in collaboration with a team of > experts in bacteriology from the universities of Nottingham and Edinburgh. > > He commented: "We conducted an experiment on bacterial communication, and > found that they communicate in a way that was previously thought to be > unique to humans and perhaps some other primates. > > "This has serious implications for our understanding of the origins of > human communication and language. In particular, it shows that we can > assume that combining signals together is unique to the primate lineage." > > More information: 'Combinatorial communication in bacteria: Implications > for the origins of linguistic generativity', Scott-Phillips et al, > published in PLOS One, 23 April 2014. > www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0095929 > > Provided by Durham University > > "Microbes provide insights into evolution of human language." April 23rd, > 2014. > http://phys.org/news/2014-04-microbes-insights-evolution-human-language.html > > > > The contrary would have astonished me a lot, but it is nice this is > confirmed and studied (I was sure it was). Comparison with language might > be slightly stretched as there is no symbolic role in the messages, but may > be it can make sense (I am not sure, I will read the paper ... but that > does not seem really in his topics). I have few doubts that our own cells > communicate in very sophisticate chemical ways, and there are evidences > that plants does communicate through their roots, may be even through > bacteria. (But no proof of such explicit double "words" nuancing, although > again, its non existence would be astonishing). I would have bet this was > already discovered on Escherichia Coli, but not in that apparently explicit > way. > Hmm... I'm not sure that they verified enough that the two compounds don't > react to get a third molecule, which would trivialize the discovery. > So interesting, but has to be continued and confirmed, ... > > Bruno > > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > http://iridia.ulb.ac.be/~marchal/ > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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