#195884 - 12/01/10 08:02 PM
Study Confirms E. Coli Evolution Via Natural Selec
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ævory
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Registered: 04/04/05
Posts: 9657
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Science
Study Confirms E. Coli Evolution Via Natural Selection
Jason Mick (Blog) - June 17, 2010 4:45 PM
A 3D-rendering of the E. Coli bacteria (Source: JEFF JOHNSON Hybrid Medical Animation)
Stained E. Coli bacteria (Source: LBL)
GroEL and GroES, E. Coli Heat Shock Proteins (HSPs), visualized (Source: Tulane University)
The Chaperonins play a critical role in bacterial heat shock systems (see the bottom left). (Source: Biomol)
Results offer important insight into evolution, could lead to hardier genetically engineered animals
Natural selection -- the theory that organisms retain favorable traits by surviving and reproducing and conversely removal of unfavorable traits by the opposite effect -- is thought to play a critical role in evolution. As just a handful of modified proteins or protein levels can cause profound anatomical and physiological changes, natural selection may in part have helped mammals to evolve from early reptiles, a road which would eventually lead to ancient hominids and, finally, man.
A new study has provided one of the first compelling examples of what appears to be natural selection in a controlled laboratory setting. Researchers at the Technische Universitaet Muenchen's (TUM) ("Technical University of Munich") Department of Chemistry and Center for Integrated Protein Science Munich, Germany, carried out the study.
They began by taking a single E. coli bacteria, the type of bacteria that resides in the human gut. E. coli typically enjoys life at our pleasant body temperature of around 37 degrees Celsius.
They then slowly turned up the heat on the bacteria, inducing heat shock. Three lines of bacteria, propagated from a common ancestor and living under heat shock conditions were cultured over hundreds of generations. Wild-type E. coli can only survive up to 44 to 46 degrees Celsius. But by carefully bumping up the temperature over two years to 48.5 degrees, the E. coli developed adaptations that allowed them to survive.
A control line of bacteria was also derived form a common ancestor and kept at 37.5 degrees Celsius. All of the bacteria were kept isolated from their sister lines and from any other outside bacterial or viral contaminants (to prevent accidental DNA transfer).
By analyzing extensively the proteins in the adapted cells, the researchers found they only had one key difference -- elevated levels of molecular "chaperone" proteins GroEL and GroES -- intracellular machines that can stabilize folding proteins under stress. Mutations were shown to have allowed for increased transcription of these proteins.
All three lines showed elevated levels of protein -- with an average of a 16-fold increase from the control line. The GroE proteins appear to play a unique role in surviving hotter conditions. Interestingly the study also confirmed the idea that natural selection is a game of tradeoffs -- by increasing the level of heat shock proteins, the cell consumed valuable resources. While this allowed it to survive, it came at the cost of reduced growth.
The changes were shown to persist for over 600 generations -- indicating that E. coli that lost the changes likely died of heat shock and were likely selected out.
Dr. Jeannette Winter, who helped lead the research says that the results not only provide evidence in support of the theory of natural selection, and the broader theory of evolution, but also could yield genetic engineering advances. She states, "The correlation between genetic changes and chaperones has been shown not only in bacteria, but also in eukaryotes such as yeast, fruit flies, and fungi. Better understanding of chaperones might also open the way to targeted generation of organisms for specific purposes -- enhancing their ability, for example, to live under stressful conditions, to break down harmful pollutants, or to produce specific, biotechnologically relevant proteins."
The study is published here in the June 18 edition of the Journal of Biological Chemistry.
http://www.dailytech.com/Study+Confirms+E+Coli+Evolution+Via+Natural+Selection/article18761.htm
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#195885 - 12/01/10 08:04 PM
Re: Study Confirms E. Coli Evolution Via Natural Selec
[Re: ævory]
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ævory
Member
Registered: 04/04/05
Posts: 9657
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Science
Canadian Researchers Recreate Climate Change-Driven Fish Evolution
Jason Mick (Blog) - August 5, 2010 7:37 AM
A new study shows that sticklebacks can quickly evolve to deal with colder water (marine male stickleback, pictured). (Source: Rowan Barrett, UBC)
A male (bottom) and female (top) stickleback get friendly with each other. Perhaps they're preparing to help the evolutionary cause? (Source: Rowan Barrett, UBC)
UBC researchers wrangle some sticklebacks out on the pond. (Source: Rowan Barrett, UBC)
Observed evolution recreates a natural process that occurred over the last 10,000 years
Life in the cold freshwater lakes of northern Europe, northern Asia, Canada, and Alaska is challenging for unprepared lifeforms. Fortunately marine sticklebacks came equipped with a power tool -- evolution -- which allowed them to adapt and colonize this chilly environment.
Researchers at the University of British Columbia, along with colleagues from Switzerland and Sweden, "recreated history" by transplanting marine sticklebacks to freshwater ponds. Within only three generations -- or roughly three year's time -- the little fish had evolved mechanism to cope with the 2.5 °C colder water. The resultant population was roughly equivalent to the naturally evolved freshwater sticklebacks in terms of temperature tolerance.
A similar process is thought to have given rise to the first freshwater sticklebacks, which are thought to have diverged from marine sticklebacks 10,000 years ago. At the end of the last ice age melting glaciers produced lakes and streams in the northern landmasses. Sticklebacks slowly colonized these new bodies of water, adjusting to the colder temperature of their new home.
Rowan Barrett, a researcher with the UBC Department of Zoology and lead author of the work,states, "By testing the temperature tolerance of wild and lab-raised sticklebacks, we were able to determine that freshwater sticklebacks can tolerate lower temperatures than their marine counterparts. This made sense from an evolutionary perspective because their ancestors were able to adapt to freshwater lakes, which typically reach colder temperatures than the ocean."
Barret, a new Ph.D, adds, "Scientific models have suggested that climate change could result in both a general, gradual increase of average temperatures and an increase in extreme temperatures. Our study is the first to experimentally show that certain species in the wild could adapt to climate change very rapidly – in this case, colder water temperature. However, this rapid adaptation is not achieved without a cost. Only rare individuals that possess the ability to tolerate rapid changes in temperature survive, and the number of survivors may not be large enough to sustain the population. It is crucial that knowledge of evolutionary processes is incorporated into conservation and management policy."
Climate change is a popular topic right now, as the research community widely leans towards the hypothesis that the world is warming right now. Thus the UBC study seems particularly interesting and pertinent as it shows that animals will likely evolve to adjust to the Earth's warmer conditions, if the Earth is indeed warming.
While some believe that the case for evolution is weak, there is ia vast body of evidence including field biology (direct observation), genetics, botany, morphology, paleontology, and biochemistry that indicates it's a virtual certainty that nature has employed and will continue to employ this essential asset.
Sticklebacks were among the first examples of creatures directly observed to have evolved significantly. E. Coli are another such model organism that has showed the ability to evolve significant new abilities in a brief amount of time.
The new work is reported in the peer-reviewed journal Proceedings of the Royal Society B.
http://www.dailytech.com/Canadian+Resear...rticle19266.htm
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#195937 - 12/03/10 04:57 PM
Re: Study Confirms E. Coli Evolution Via Natural Selec
[Re: ævory]
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Paul I
Member
Registered: 02/24/00
Posts: 7913
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What's curious is that evolution occurs in bursts sometime. Why?
_________________________
"...only the shadow knows"
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#195965 - 12/04/10 11:56 AM
Re: Study Confirms E. Coli Evolution Via Natural Selec
[Re: Paul I]
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Deo
Member
Registered: 02/11/08
Posts: 127
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Paul I, its the genetic system of the species which is the most important determinant of its rate of evolutionary change ie sexual vs asexual and haploid vs diploid. Evolutionary changes occurs fastest in asexual haploids (bacteria) than us sexual diploids. Any changes that increases the reproductive success of a species is retained in the population.
Deo
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