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:
Pictures: Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Jena (Germany); Tel.: +49 3641 57-2110; firstname.lastname@example.org
Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Researchers target protein that protects bacteria's DNA 'recipes'
21.08.2018 | University of Rochester
Protein interaction helps Yersinia cause disease
21.08.2018 | Schwedischer Forschungsrat - The Swedish Research Council
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
21.08.2018 | Ecology, The Environment and Conservation
21.08.2018 | Life Sciences
21.08.2018 | Power and Electrical Engineering