Scientists of the Weizmann Institute of Science initiated a competition of evolution in a test tube. Its results show that random mutations that give an advantage in one environment, may not be useful in another environment - while sexual reproduction may produce stable solutions in diverse conditions
Evolution may seem, at times, to be a kind of competition in adaptation. Sometimes it reaches a real survival game (that is, not just "reality"). Scientists who want to learn about the mechanisms that drive this process, encounter a high hurdle - in the animal and plant world, evolutionary processes last a very long time, beyond the duration of human life. One of the ways to deal with this difficulty is to conduct studies on organisms whose life cycle is short and fast. For example, bacteria and fungi (such as yeast).
The research carried out on bacteria in the laboratory has additional advantages from the point of view of the scientists: it is possible to raise a "control" group alongside the research population, and it is possible to have good control over the manipulations applied to the organisms being studied (temperature, salinity, acidity). The first to carry out evolution in a test tube was Sol Spiegelman who in his laboratory carried out the evolution of a single RNA molecule which gradually acquired the ability to be replicated by an enzyme. Richard Lansky advanced the field with a well-known experiment, which has been carried out for 30 consecutive years.
A new phase in the field began about three years ago, when Prof. Tzachi Flafel, staff scientist Dr. Orna Dehan, and research student Sion Kaminsky-Strauss, from the Department of Molecular Genetics at the Weizmann Institute of Science, posed an evolutionary challenge to the community of in vitro evolution researchers. They provided everyone who expressed a willingness to face With the challenge (about 30 laboratories worldwide), a group of E. coli bacteria, or Yeast, from those growth lines, which were marked for identification. The participants were asked to live in an environment where the temperature was much colder than their comfortable temperature. From then on, the scientists participating in the challenge could change various factors in the system, which would help the bacteria or yeast to evolve and adapt to life in the cold environment. According to the definition of the challenge, it was only possible to help and promote the self-improvement of the bacteria - but it was forbidden to harm the competitors.
Three months later, the challenge participants were asked to return the bacteria that had adapted and survived the frost to Prof. Pepper's laboratory. Here two parallel tournaments began: the bacteria or yeast, which came from the different laboratories, and which were marked with a kind of genetic "barcode", for identification, were introduced into the same cold environment. The microorganisms that managed to survive more difficult conditions testified to the degree of success of the scientists who "trained" them.
In life, as we know, there are surprises: Prof. Pepper and the members of his research group decided to test the ability of the bacteria that were "trained" to live in a colder environment than stipulated in the original challenge - and even added another difficulty: the necessity to survive in a particularly salty environment
The bacteria that were "trained" by the research student Yanon Bar-On from the laboratory of Prof. Ron Milo from the Department of Plant Sciences at the institute came in first place in this category. He exposed "his" bacteria to different levels of expression of a gene that replicates DNA relatively carelessly, that is, with many errors. This strategy was based on the ambiguity as to the degree of precision desired in DNA duplication. This strategy made it possible to identify the bacteria that used - by chance - an ideal degree of precision (or carelessness). Second place came to bacteria trained by female scientists from Kyle University (Prof. Tal Dagan and research student Tanita Wein). This team performed many rounds of competition between subpopulations, with each round, the best being passed on and the rest going extinct.
In the yeast tournament, the first three places were reached by research teams from Harvard, EMBL and Tel Aviv University, which employed different strategies of sexual reproduction. They paired the original yeast with different yeasts from nature and sorted out the most successful offspring.
So far everything has gone as expected and as planned. But life, as we know, has surprises. In this case, Prof. Pepper and the members of his research group decided to test the ability of the bacteria that were "trained" by the various scientists, to withstand living conditions in an environment where the temperature is even lower than the challenge temperature (which was known to the competitors, and to which they aimed and trained "their" bacteria) ). If that wasn't enough, they added another evolutionary survival competition, fundamentally different from what the competitors were known for: The necessity of living in a living environment characterized by high salinity.
"We wanted to examine whether the 'training' carried out by the competitors trained 'their' bacteria to adapt to harsh living environments in general," says Prof. Pepper.
In the yeast division, sexual reproduction continued to prove itself. The winner, even under conditions that were not known in advance, was a species created through sexual reproduction. In bacteria, the picture was more complex: in some of the new conditions, none of the strategies proved useful; And in others, the success rating varied. One of the conclusions from these results is that while random mutations, such as those found in bacteria, provide an advantage in a certain environment, they may not be beneficial, and perhaps even harmful, in other environments. In contrast, sexual reproduction, which creates genetic diversity only by mixing existing genetic information, may produce stable solutions even under new conditions.
The scientists say this experiment provides the evolutionary research community with a broad spectrum of additional methods for conducting such experiments in the future. The methods presented in this framework may also be useful in various biotechnological processes.
So far, about 100 billion people have lived in the world in all periods together. In an evolution experiment in the laboratory, it is possible to monitor a similar, and even higher, number of bacteria that are formed and compete with each other.
More of the topic in Hayadan:
- Nobel Prize in Chemistry 2018 to three researchers for harnessing evolution to develop environmentally friendly catalysts, proteins and antibodies
- Gene transfer between species is much more common than we thought and has accelerated evolution
- A billion-year arms race against viruses has shaped our evolution
One response
It's a shame that we didn't say what the conclusion is - random mutations lead to successful results in harsh living conditions, more than slow exposure to these conditions?