Navigation Links
Experiment turns up the heat on natural selection, reveals new details of an evolutionary mechanism
Date:6/17/2010

Scientists in Munich report evidence that high concentrations of the molecular "chaperone" proteins GroEL and GroES -- intracellular machines that can stabilize folding proteins under stress -- play a critical role in increasing the maximum temperature at which E. coli bacteria can grow. Massively and permanently elevated levels of the GroE proteins were found in bacteria adapted, step-wise over a period of years, for growth at 48.5 degrees C. This genomic change persisted for more than 600 generations, and molecular analyses ruled out other mechanisms that might account for the increase in heat resistance. The researchers' findings, published in the June 18 edition of the Journal of Biological Chemistry, have important implications for both fundamental evolutionary studies and biotechnology applications.

In addition to being a well established resident of the human digestive tract, Escherichia coli is at home in the lab. It is a model organism as important to biological research as brewer's yeast, the fruit fly, and the mouse. Having evolved for life at our body temperature of around 37 degrees C., wild-type E. coli can be cultivated in the laboratory at temperatures up to but not beyond 44 to 46 degrees C. Pushing the upper temperature at which E. coli could grow to 48.5 degrees C. does not approach the level of heat resistance found in thermophile species, but what this experiment required was a distinct and significant redefinition of "extreme" for E. coli.

To achieve that, Dr. Jeannette Winter and colleagues at the Technische Universitaet Muenchen (TUM) founded three lines of E. coli bacteria from a common ancestor and propagated them under heat stress for hundreds of generations. The step-wise process they designed created conditions under which a combination of normal genomic instability and natural selection would be likely to produce adaptations for growth at extreme temperatures. It took around two years to reach 48.5 degrees C, but after that, adaptation to this new extreme was inherited. The researchers propagated a control population, also descended from the common ancestor, at 37 degrees C.

Exhaustive analysis of cell physiology, protein expression, and genome sequences revealed a number of significant changes. Compared with the control group, the adapted lines of E. coli showed a clearly enhanced capability for living under conditions of heat stress. This was accompanied by reduced growth rates, showing that survival came at a cost in terms of overall fitness, a typical indicator of genomic mutations. One of the most striking changes measured was a 16-fold increase in GroE levels, more than five times what a normal heat shock response in E. coli would be expected to produce. Further analyses of heat shock genes and proteins ruled out other mechanisms -- beyond the role of GroE alone -- as being critical for evolution for life at 48.5 degrees C.

GroE chaperones are known to play an active role in assisting the folding process of other proteins, especially in cases where mutations that could cause improper folding threaten the survival of the cell. This experiment shows that they likely play a uniquely important role -- by mitigating the potentially damaging effects of accumulating mutations on protein folding -- in the evolution of heat resistance in E. coli.

"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," says Dr. Jeannette Winter, a researcher in the TUM Department of Chemistry and a member of the Center for Integrated Protein Science Munich. Beyond yielding insights into evolutionary history, Winter says, further research on these highly conserved mechanisms could shed light on how organisms evolve in response to climate-related stresses in the future. "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."

This research was supported by the Emmy-Noether program of the German Research Foundation (DFG), the Elitenetzwerk Bayern, the Fonds der chemischen Industrie, and SFB 594.


'/>"/>

Contact: Patrick Regan
regan@zv.tum.de
49-892-891-0515
Technische Universitaet Muenchen
Source:Eurekalert

Related biology news :

1. Experimental treatment protects monkeys from lethal Ebola virus post-exposure
2. The great pond experiment: Regional vs. local biodiversity
3. Selected highlights of the research being presented at the Experimental Biology 2010 meeting
4. Experimental vaccine protects monkeys against chikungunya
5. ModiFace Launches iLab: An iPhone and iPad App Experimentation Laboratory
6. Experimental drug shows promise against brain, prostate cancers
7. French scientist wins the Journal of Experimental Biology Outstanding Paper Prize 2009
8. Experimental treatments restore partial vision to blind people
9. Free AAPS Webinar will discuss design of experiments
10. New stem cell research could reduce number of animal experiments
11. Experimental treatment halts hypoxic-ischemic brain injury in newborns
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/9/2016)... June 9, 2016  Perkotek an innovation leader in attendance control systems is proud ... work hours, for employers to make sure the right employees are actually signing in, ... ... ... ...
(Date:6/2/2016)... , June 2, 2016   The Weather Company , ... Watson Ads, an industry-first capability in which consumers will be ... able to ask questions via voice or text and receive ... Marketers have long sought an advertising ... that can be personal, relevant and valuable; and can scale ...
(Date:5/16/2016)... , May 16, 2016   EyeLock LLC , ... announced the opening of an IoT Center of Excellence ... and expand the development of embedded iris biometric applications. ... level of convenience and security with unmatched biometric accuracy, ... identity aside from DNA. EyeLock,s platform uses video technology ...
Breaking Biology News(10 mins):
(Date:6/24/2016)... ... 24, 2016 , ... Researchers at the Universita Politecnica delle Marche in Ancona ... or pleural mesothelioma. Their findings are the subject of a new article on the ... are signposts in the blood, lung fluid or tissue of mesothelioma patients that can ...
(Date:6/23/2016)... 23, 2016 A person commits a crime, and ... to track the criminal down. An outbreak of ... Drug Administration (FDA) uses DNA evidence to track down the ... Sound far-fetched? It,s not. The FDA has increasingly used a ... of foodborne illnesses. Put as simply as possible, whole genome ...
(Date:6/23/2016)... 23, 2016   EpiBiome , a precision microbiome ... in debt financing from Silicon Valley Bank (SVB). The ... to advance its drug development efforts, as well as ... "SVB has been an incredible strategic partner to ... traditional bank would provide," said Dr. Aeron Tynes ...
(Date:6/23/2016)... June 23, 2016  Blueprint Bio, a company dedicated ... the medical community, has closed its Series A funding ... . "We have received a commitment from ... we need to meet our current goals," stated ... the runway to complete validation on the current projects ...
Breaking Biology Technology: