Bacteria are able to detect impending change and prepare for its arrival. This is what a new study by scientists from the Weizmann Institute of Science and Tel Aviv University shows. These findings are published today in the scientific journal Nature.
Prof. Yitzhak Papel, research associate Dr. Orna Dahan, research student Amir Mitchell and other members of Prof. Papel's research group, from the Department of Molecular Genetics at the Weizmann Institute of Science, as well as Prof. Martin Kopeik and research student Gal Romano from Tel Aviv University tested microorganisms that live in environments that change in predictable ways. Their findings show that the genetic networks of these microorganisms are structured in such a way that they are able to "predict" the next step in the sequence of events, and that the bacteria begin to respond to the new situation even before it arrives.
The research was carried out with Escherichia coli bacteria, microorganisms that normally wander along our digestive tract without causing harm. The digestive system is a changing environment, and some of the changes are understandable and come one after the other with a certain regularity. For example, maltose sugar appears in many cases after the appearance of another sugar - lactose. The scientists tested the bacteria's genetic response to lactose, and found that in addition to the genes that allow it to digest lactose, the gene network that produces proteins essential for maltose digestion was also (partially) activated. When they reversed the order of the sugars and initially gave the bacteria maltose, the genes that produce proteins necessary for lactose digestion were not activated. This finding shows that the bacteria "learned" naturally that after an "opening dose" of lactose, a dose of maltose sugar will appear.
Another microorganism that "learned" to recognize an expected change is the wine yeast. During the fermentation process, the sugar and acidity levels change, the alcohol level rises - and the fermentation environment heats up. Although in this case the environment is more complex than that of the E.coli bacteria, the scientists found that when the heat in the environment of the wine yeast begins to rise, the genetic systems of the yeast already begin to prepare the necessary "tools" to effectively deal with the change taking place. Further analysis of the data showed that the ability to anticipate the future (the next step in the process), and the advance preparation for change, are, in fact, evolutionary adaptations that increase the organisms' chances of survival.
The Russian scientist Ivan Petrovich Pavlov first demonstrated this learned expectation, called "conditioned response", in dogs. He trained the dogs to secrete saliva in response to a stimulus - the ringing of a bell - before serving them food. This work earned him the Nobel Prize in Physiology or Medicine in 1904.
"In microorganisms," says Prof. Pepper from the Weizmann Institute of Science, "evolution that lasts for many generations can replace learning based on training." Research student Amir Mitchell from the Weizmann Institute of Science: "The evolution of a single cell that lasts thousands of generations is, to a certain extent, similar to learning. In both of these processes, organisms adapt their response to environmental stimuli, thus improving their chances
their survival". Research student Gal Romano from Tel Aviv University: "This is not a general response to stressful situations, but a precise and targeted process. The yeast prepares in a unique way for the specific conditions that will come after the sign they received."
To test whether the microorganisms had indeed acquired a type of conditioned response, Amir Mitchell suggested performing another test, which was based on Pavlov's follow-up experiment. When Pavlov stopped giving the dogs food after ringing a bell, the conditioned response faded until they did not respond to the ring at all. The scientists ran a similar experiment on the bacteria. To this end, they used bacteria grown by Dr. Erez Dekal in the laboratory of Prof. Uri Alon in the Department of Molecular Biology of the Cell at the Weizmann Institute of Science. He raised them in an environment that contained the first sugar, lactose, but did not give them maltose, the second sugar. After several months in which dozens of generations changed among the bacteria, evolution led to the fact that they stopped activating the genes necessary for maltose digestion, when they received a taste of lactose, and activated them only after actually receiving maltose.
"These findings showed us that preparation in advance is not beneficial for bacteria under any conditions," says Prof. Pepper. "It costs them a certain amount of energy, so they activate it - and pay its price - only when there is a justification for it, and the second sugar does come after the first sugar." When should bacteria really prepare in advance for the next step? To answer this question, and to predict in advance when it would be worthwhile for the bacteria to prepare for what is to come, the scientists developed a kind of model of costs and benefits. This model has been tested in experiments and has already succeeded in predicting the activation of the various gene networks.
Prof. Pepper and the members of the research group he heads believe that the genetic conditional response may be a common mechanism for evolutionary adaptation that improves survival in many organisms, and it is possible that it also works in the cells of different organisms, including humans. These findings may help improve the efficiency of using genetically modified bacteria for fuel production processes from plant materials.
On the same topic on the science site
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Tomer:
This is the same award:
http://en.wikipedia.org/wiki/Nobel_Prize_in_Physiology_or_Medicine
"This work earned him the Nobel Prize in Physiology or Medicine in 1904."
Was the Nobel in physiology or medicine?
In the midst of enthusiasm…
First of all, a link: http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature08112.pdf
Secondly, it is possible to think of a mechanism in which exposure to an initial condition activates a genetic change - a kind of switch.
It's very nice, but I wouldn't call it "learning"
Indeed the article in Haretz is more accurate than the article here also in the differences between the learning in Pavlov's dogs and the evolution in bacteria here. Many questions would not arise.
Receive Michael Baharez's referral again
http://www.haaretz.co.il/hasite/spages/1094170.html
Better read there
Shabbat Shalom
Sabdarmish Yehuda
Yehuda:
Lucky that whoever came up with the idea of the experiment was able to see the similarity.
I see only a small resemblance between Pavlov's experiment with dogs and the experiment with germs. There the dogs were taught to behave, there was no evolution, whereas here the bacteria went through an evolutionary process in which only the fit survived.
Shabbat Shalom
Sabdarmish Yehuda
Pavlov:
It is indeed a very similar study that uses the same idea and I am quite sure that the idea presented here as an idea of Amir Mitchell is simply plagiarized.
There is of course a small difference in the features that were tested so this publication is still worth it.
Also in the reports on the original research of Tabazoi from Princeton (published in Science as I wrote before) Pavlov was used as an example of the bacteria's ability to connect one signal to an expected signal. What is unclear to me is how a study that repeats and reinforces the findings that were already published a year ago manages to be published in Nature?
http://telem.openu.ac.il/courses/c20237/Pavlovbact-g.htm
The article from Science:
http://genomics.princeton.edu/tavazoie/web/media/Publications/Tagkopoulos_etal.pdf
Yigal:
I wouldn't say something that clearly yields cows (in the form of research ideas) is bad.
Michael,
Even as a metaphor, the use is quite bad because there is no learning process here, but only a choice of the qualified - those who have experienced one thing and prepared for the next thing. Pavlovian learning is completely different: unlike learning, in which each individual must go through all its stages from the beginning, in this case each individual is already born (or created from the beginning) with all the necessary qualities - without learning.
Yigal and Raan:
I actually think the metaphor of learning through evolution is helpful.
As long as it is clear that it is only a metaphor (and here it is clear) it allows people to express themselves more succinctly and connect conclusions from the two fields.
A historical fact that appears in the article is that this parallel is the source of the idea for the experiment so that even in this article there is proof of its fruitfulness.
fresh (2)
It may be that there is no novelty in this, or that similar things have already been published in the past, but there is no doubt that there is no resemblance to your hands, even though it is clear that both features (the ability to "predict" and the hands) developed through natural selection: the hands are not a process that reacts to an external event and prepares itself for an expected event(s) /sea. The hands are there all the time. The innovation in the knowledge (in my opinion) is that among the features that developed during evolution there is also the ability to react indirectly. Not a direct response to current conditions but to respond based on current conditions to expected conditions.
And you are right, there is no learning here but a type of adaptation and there is no place to compare it to Pavlovian learning.
In "Haaretz" they found a more appropriate title:
http://www.haaretz.co.il/hasite/spages/1094170.html
The title is misleading. It's like man can predict the future, when the truth is man can only use past data. It has nothing to do with the future.
fresh:
Not every piece of news should herald innovation on a philosophical level.
Also confirmation of theories of existence and simply accumulation of accurate knowledge about different organisms warrants research.
It's true that my evolution made me expect something more bombastic after such a title, but that's just a matter of the title, and upon further thought, I'm not clear to what extent it is possible to formulate a title that will both report what happened and lower expectations to the right level.
It is also available on Ynet
http://www.ynet.co.il/articles/0,7340,L-3732936,00.html
They already published something similar a year ago in Science.
News from Galileo about the previous study:
ttp://telem.openu.ac.il/courses/c20237/Pavlovbact-g.htm
To the editor: Avi Blizovsky
Why is there no direct reference to the source from which the article was copied?
There is no innovation in this research, it is simply an adaptation of the bacteria to the environment, in a normal evolutionary process. It's just like saying that humans were born with hands because they foresaw the future where hands would be important to them to work with.
There is no learning here, at least not in the usual sense of the word.
Nobel prize?