On 25 Apr 2014, at 07:39, Samiya Illias wrote:
Does scientific research back the claims made in this article?
Yes. Social amoeba are unicellular (capitalist) in good time, and
become communist in hard time. May be we should learn from them.
I say yes but there are some details which I have not the time to
verify, of course. Notably the elimination of the cheater mutant. That
is quite plausible though. The Dictyostelium discoideum is a quite
fascinating organism, or should we say colony of organisms?
The communication means here are still very rudimentary, though, and I
don't think there are evidence for the "double word" communication
mentioned in the thread.
Bruno
Samiya
Amoebic Morality <http://www.damninteresting.com/amoebic-morality/ >
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.
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.
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, 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
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