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Science Forum Index » Bio Evolution Forum » Paper: Evolution of species interactions in a biofilm commun
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| Robert Karl Stonjek |
 Posted: Thu Feb 01, 2007 12:46 pm |
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Nature 445, 533-536 (1 February 2007) | doi:10.1038/nature05514; Received 13
September 2006; Accepted 8 December 2006
Evolution of species interactions in a biofilm community
Susse Kirkelund Hansen, Paul B. Rainey, Janus A. J. Haagensen and Søren
Molin
Biofilms are spatially structured communities of microbes whose function is
dependent on a complex web of symbiotic interactions. Localized interactions
within these assemblages are predicted to affect the coexistence of the
component species, community structure and function, but there have been few
explicit empirical analyses of the evolution of interactions. Here we show,
with the use of a two-species community, that selection in a spatially
structured environment leads to the evolution of an exploitative
interaction. Simple mutations in the genome of one species caused it to
adapt to the presence of the other, forming an intimate and specialized
association. The derived community was more stable and more productive than
the ancestral community. Our results show that evolution in a spatially
structured environment can stabilize interactions between species, provoke
marked changes in their symbiotic nature and affect community function.
Source: Nature
http://www.nature.com/nature/journal/v445/n7127/abs/nature05514.html
In it together
(Editor's Summary of the above paper)
Biofilms are specialized environments where communities of microorganisms
are insulated from the outside world by an extracellular polymer matrix that
they themselves secrete. The resulting microbial mats have been compared to
tropical rainforests in terms of complexity and biodiversity. Selective
pressures on such biofilms are likely to demand intense interactions between
the individual bacteria, and an experiment with a simple community of two
species (soil dwellers Pseudomonas putida and Acinetobacter sp.) shows just
how close that relationship is. The physical structure of the community
altered, to the mutual benefit of both species, as a result of a simple
mutation in the genome of one of the species. In the absence of a partner
the mutation (in P. putida) would have been deleterious. This system
demonstrates the importance of interspecies interactions, and may be useful
in work on the evolution of these interactions.
Source: Nature
http://www.nature.com/nature/journal/v445/n7127/edsumm/e070201-12.html
Posted by
Robert Karl Stonjek |
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| g |
| Posted: Sun Feb 04, 2007 10:19 am |
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"Robert Karl Stonjek" <rstonjek@bigpond.net.au> wrote in message
news:eptqk3$u8u$1@darwin.ediacara.org...
As much as this layman appreciates an opportunity to know that an article
has been published in Nature, regarding a mutually beneficial mutation
occurring to one of two species which is beneficial in the symbiotic
context, but would have been deleterious to the mutating species, had it
occurred outside the context of the sequestered symbiosis, ALAS, this layman
is not a subscriber to Nature (one of several peer reviewed journals he
would subscribe to, if budget were not at issue).
This is frustrating.
In absence of some unknown mechanism, even beyond the farthest stretch of
the mutating DNA having some way of reading in advance the potential benefit
of a mutually beneficial mutation and then complying with that need, what
would be the odds of a mutation occurring beneficial to either, much less to
both, and much, much, MUCH less coming up with a mutation mutually
beneficial, which otherwise would be deleterious.
If mutations are NOT a result of a READING of NEED for a solution to an
issue -- NOT a result of an ANTICIPATORY benefit that would be nice to
have in tandem, where survival had occurred without same -- FOLLOWED BY an
appropriate RESPONSE in the form of coming up with just the right mutation
to do the job nicely... what would be the odds of same as over against the
odds of a random mutation in the same environment?
It does not seem strange that a mutation should occur.
What is STRANGE (provided mutations are random, unguided as to what is
appropriate) is that a mutation would occur that would NOT be enormously
statistically likely to be deleterious, whether to the mutating species, to
the symbiosis of the two, or to the unmutating species.
Am I being clear? What are the statistical odds of just the right mutation
for mutual benefit and precisely beneficial to the symbiotic union.
My imagination suggests that the odds would be as many as are the possible
permutations involved.
What would be of interest would be the nature of the mutation. Was it a
copying "error," a "deletion" a permutation wherein two letter got swapped
in their places? How many OTHER kinds of mutations might have been possible
under the circumstances?
If many, many experiments of this kind result in mutually beneficial
mutations, this would have a very weird connotation:
A. Can a species' or its DNA READ its environment and discern any issues
needing to be "fixed" by a particular mutation?
B. Can a species or its DNA READ its environment and ANTICIPATE a new
mutation (as opposed to a survival-based adaptive need, that would be
beneficial to it, en solido?
C. Can a species or its DNA READ a symbiotic relationship, and that
symbiotic relationship in tandem within an a shared environment, and make a
determination of what particular mutation would be advantageous there? AND,
D. IF THE ANSWER TO A and/or B and/or C, above, is "yes," THEN can
the READING/ANALYZING/CREATIVE ISSUE-SOLVING species or its DNA
PROACTIVELY MANUFACTURE THE PRECISE MUTATION NEEDED FOR SURVIVAL OR
ANTICIPATED FOR GAIN IN FITNESS?
To say that this would be startling and that it would inform new research
toward an understanding of the mechanism or mechanisms which would enable
such proactive behavior would be not only the understatement of the day. It
would be the understatement of the MILLENNIUM !
On the other hand, if the phenomenon observed is a grossly atypical one,
then it could be only a statistically
unlikely, but quite statistically probability out of a sufficient number of
"runs."
Would you like to guess which scenario is most likely?
Any other reader/poster to this news group wish to offer any scenario other
than these I have offered. (Given so few details, and so little background
as to what has happened in other, similar experiments... if any... these are
the only two scenarios this old layman can think of so far.)
This is pretty heavy stuff, if not a fluke.
Just think of it: DNA that can *observe, analyze, anticipate, calculate a
mutational solution and emplement that specific mutation* ????
Jimminy CHRISTMAS !
g |
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| Guest |
| Posted: Wed Feb 07, 2007 8:54 am |
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Quote: Am I being clear?
I think so. You are trying to do what a mathematician would call a
hypothesis test. Some event occurred, and you are trying to calculate
the odds that it was a nonrandom occurence. However, you are starting
with a false assumption.
Quote: What are the statistical odds of just the right mutation
for mutual benefit and precisely beneficial to the symbiotic union.
To calculate the odds, one would have to include all the right
mutations including those that did not occur. The authors of the paper
may know what changes actually occurred in biofilm being studied.
However, this is not enough to do a hypothesis test (i.e., evaluate
whether or not this is a nonrandom event). if someone tried to
calculate the odds before the experiment, one would have to know what
all the possibilities were including those mutations that would be
beneficial yet didn't occur.
For example, suppose in the real population some chemical was
used to communicate between species. There are a lot of chemicals that
could have been used to communicate. The large number of alternatives
greatly increases the possibility that some beneficial mutation would
occur. >
Quote: My imagination suggests that the odds would be as many as are the possible
permutations involved.
My imagination says that the odds are some factor of the many
permutations involved, not the permutation itself. When one is
calculating odds, one generally has to calculate the combinations, not
just the permutations.
In mathematics, the factor of the permutation that gets to be
part of the odds. is called a combination. The reason is that each
possible benefit decreases the odds by a factor, whether or not that
benefit actually occurs. A lot of mistakes in gambling occur because
the person plugs in the complete permutation, and not the
combination. |
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