Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bacteria Expect the Unexpected

05.11.2009
Scientists observe the emergence of a new adaptation strategy to rapidly changing environmental conditions

Organisms ensure the survival of their species by genetically adapting to the environment. If environmental conditions change too rapidly, the extinction of a species may be the consequence. A strategy to successfully cope with such a challenge is the generation of variable offspring that can survive in different environments. Even though a portion of the offspring may have a decreased chance to survive, the survival of the species as a whole is guaranteed.


Within a generation, genetically identical offspring is produced that varies in the degree of adaptation to the current environment. Anticipating drastic changes of the environmental conditions in future, some variants have an increased chance to survive if the event occurs. This ensures the survival of the species as a whole. Hubertus J. E. Beaumont

For the first time scientists have now observed the evolution of such a strategy under lab conditions in an experiment with the bacterial species Pseudomonas fluorescens: A bacterial strain exposed to rapidly changing environmental conditions developed the ability to generate variable offspring without additional mutations. This new strategy ensured the survival of the bacterial strain.

The results were published in NATURE.

A popular saying already tells an interesting truth, when it recommends "not to put all your eggs in one basket", that is to say spread and hence reduce risks. Also in biology, such strategies are already known and referred to as "bet-hedging". In the process of evolution, bet-hedging is not the usual way of adapting to the environment, in which carriers of advantageous mutations prevail against other individuals that do not show these mutations. In fact, bet-hedging means that a generation produces offspring that is genetically identical, but differs in the ability to prosper in the current environments: Some offspring is optimally adapted to the current environment, while others thrive under completely different conditions. In case of rapid and drastic changes of the environment, the latter offspring is at an advantage and hence the species survives. The evolutionary advantage of the bet-hedging strategy increases, the more drastically and unpredictably the environmental conditions change. Such risk-spreading mechanisms are, for example, known from bacterial pathogens: By varying their cell surfaces, genetically identical pathogen cells escape the human immune system. Further examples of bet-hedging are known from the animal and plant kingdom.

Christian Kost, scientist at the Max Planck Institute for Chemical Ecology in Jena, Germany, has been working on this topic. Funded by the Alexander von Humboldt Foundation, he studied bacteria of the species Pseudomonas fluorescens at the New Zealand Institute for Advanced Study in Auckland. Due to their short generation time (cells divide every 52 minutes), these bacteria are particularly well suited to study evolution in the test tube. Moreover, the relatively small genome of these organisms facilitates the detection of new mutations.

Advantageous mutations become disadvantages

In their experiments the researchers exposed Pseudomonas strains alternately to unshaken or shaken culture media. Due to beneficial mutations in the genome, new variants emerged in both environments that had an advantage in either the "shaken" or "unshaken" environment. Once emerged, each new variant had to outcompete all other unmutated representatives of the ancestral strain. Under the assumption that one variant that differed in its outer appearance from its parent (for example smooth vs. rough surface) also must have outcompeted the parent strain, the most frequent representative of this new variant was picked and transferred to the respective other environment. Mutations that were advantageous in shaken media became disadvantageous in unshaken environments, and vice versa. As a consequence, new mutations and hence new variants evolved to compensate for this disadvantage. As soon as the bacteria adapted to one environment they were forced to readapt to the second one.

Bet-hedging: One genotype, several variants

The constant changes between shaken and unshaken media soon resulted in the development of types with the same genetic constitution (genotypes), which always produced two different variants. Once emerged, this was the ultimate survival strategy for the bet-hedging pseudomonades, for all other genotypes that produced new variants by mutation only had no chance to prevail against the bet-hedging variants.

Genetic analysis showed that both variants were absolutely identical on a genetic level. Furthermore, the bet-hedging genotype differed by nine mutations from the ancestral strain, with which the experiment had been started. Moreover, the final mutation in the series was causal for bet-hedging. "Our experiments provide evidence that risk-spreading is a very successful strategy to rapidly adapt to changing environments. If the same genotype generates several variants at the same time, it may survive major environmental changes", Christian Kost says. And Paul Rainey, principal investigator of the study at Massey University Auckland, adds: "The rapid and repeatable evolution of bet-hedging during our experiment suggests it may have been one of the earliest evolutionary solutions to life in constantly changing environments". [JWK/CK]

Citation:
Hubertus J. E. Beaumont, Jenna Gallie, Christian Kost, Gayle C. Ferguson, Paul B. Rainey: Experimental evolution of bet-hedging. NATURE. DOI: 10.1038/nature08504
Further Information:
Dr. Christian Kost
Max Planck Institute for Chemical Ecology, Hans-Knoell-Strasse 8, 07745 Jena (Germany); Tel.: +49 3641 57-1212; ckost@ice.mpg.de

Pictures: Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Jena (Germany); Tel.: +49 3641 57-2110; overmeyer@ice.mpg.de

Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Further information:
http://www.ice.mpg.de

More articles from Life Sciences:

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

nachricht Stingless bees have their nests protected by soldiers
24.02.2017 | Johannes Gutenberg-Universität Mainz

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>