Fanatics convinced that a god created the world as it is—the so-called creationists—have viciously attacked Richard Lenski. In 1988, this American biologist began one of the most daring experiments in history. He began to cultivate 12 populations of identical bacteria in independent containers, to observe their evolution firsthand. The project was going to last a few months, but its results were so amazing that Lenski’s team, from Michigan State University, has been taking care of their microbes every day for more than 35 years. There are about 75,000 generations, the equivalent of seeing the transformation of the human lineage over more than a million and a half years. Spanish biologist Alejandro Couce and his colleagues have now immersed themselves in Lenski’s microworld and have reached an extraordinary conclusion: “Evolution can be predictable in the short term.”
Couce, born in the A Coruña town of Irixoa 42 years ago, cites a famous thought experiment proposed by paleontologist Stephen Jay Gould in his book The wonderful lifefrom 1989. If you could rewind what happened on the face of the Earth hundreds of millions of years ago and start over, would the same thing happen? Would intelligent bipedal beings capable of writing arise again? The Quijote? Would giraffes and butterflies appear? Gould’s big question was whether evolution depends on chance or is determined.
Lenski’s work since 1988 has been titanic. The cultured bacteria is Escherichia colipresent in the human intestines. Almost seven generations live in a single day. Scientists have to change their culture medium every day, whether it is a holiday, weekend or summer vacation. The 12 populations have lived all this time basically on water, salts and glucose, but the result is surprisingly different in the 12 containers. In generation 31,500, one of the colonies learned to feed on sodium citrate, one of the ingredients of their culture medium, until then repudiated by this type of bacteria. De facto, a new species appeared, but only in one of the 12 jars.
Lenski has patiently saved frozen samples of his bacteria every 500 generations. In his cold chambers it is possible to explore what has happened since 1988 and something even more ambitious and almost philosophical: analyze whether everything could have happened differently. Couce, from the Polytechnic University of Madrid, explains that his team asked Lenski for microbes from different generations, in order to thaw them, multiply them and test hundreds of thousands of mutations on them, one by one, to analyze the effect of each of them. they.
“If you go back 75,000 human generations to 1.5 million years ago, there were still no A wise man. What we have done would be like taking a Standing manmake all the possible mutations in all their genes and ask yourself if those mutations are going to give rise to a Neanderthal, to the homo predecessor from Atapuerca or A wise man”says Couce. His team, he says, has been able to predict “up to 75% of the first adaptive steps” of bacteria. His results are published this Thursday in the magazine Sciencevanguard of the best world science.
Lenski himself, co-author of the new study, is cautious. His experiment has maintained the same conditions, fully controlled, since 1988, day after day, something very different from what happens on planet Earth, subjected to climate changes, meteorites, solar flares and an unimaginable amount of interactions between living beings. . “I am excited by these new results, but science is still far from being able to predict evolution in the vast and complex natural world. In any case, that’s how science usually works: advancing gradually, not solving everything at once,” says Lenski, who participated in the investigation of the anthrax attacks after the September 11 attacks. 2001 in the United States.
Gould’s enigma will probably never be answered. “These new data, as well as other findings from the experiment I began in 1988, show that, even under these simple conditions, evolution produces a rich and fascinating mix of the predictable and the unpredictable. I suspect that the same thing happens when evolution is expanded to the large planetary scale that Gould was thinking about,” explains Lenski.
Couce explains that his team has applied the new massive genetic engineering techniques to the so-called Long-Term Evolution Experiment. The Spanish biologist believes that his results allow him to “dream” of making concrete predictions about the evolution of pathogens and pests, as is already done with the climate. “This work opens the door to predicting what is important for a new virus to jump from the pangolin and adapt to humans,” he celebrates.
Microbiologist Sara Hernando Amado praises the “brilliant idea” of Alejandro Couce and his colleagues. “Not only do they raise one of the most interesting questions that can be asked in biology – whether it is possible to predict evolution – but they also lead us to a key question to solve one of the greatest health challenges we face: Is it possible to predict the emergence of antibiotic resistance in pathogenic bacteria?” says the researcher, from the National Center for Biotechnology, in Madrid. “We have a tool, evolutionary knowledge, that can allow us to stop or slow down the emergence of resistance associated with the use of antibiotics, simply by choosing them better,” highlights Hernando Amado.
Microbiologist Jerónimo Rodríguez Beltrán also applauds the new study, in which he did not participate. “He shows that, at least in the laboratory, evolution is to some extent predictable. As long as conditions remain constant, the tape of life would play the same song. At least the first chords,” says the researcher, from the Ramón y Cajal Institute for Health Research, in Madrid. “It is a tremendously important discovery, because it opens the door to predicting bacterial evolution, which has applications in fields as diverse as biotechnology, where bacteria are used to produce compounds of interest, or medicine, in which resistant bacteria to antibiotics are reaching an alarming prevalence,” he adds.
A report prepared for the British Government warned in 2016 that drug-resistant microbes – especially bacteria – were already killing 700,000 people each year in the world. According to the document, deaths from this cause may reach 10 million in 2050, more than those caused by cancer. Rodríguez Beltrán emphasizes that the new data are valid only for bacteria that do not exchange genetic material with each other, a very common phenomenon in other microbes and which is behind the spread of antibiotic resistance. The microbiologist, however, is optimistic: “The results of this work are a boost to scientists who are trying to predict the emergence of multi-resistant bacteria: he tells us that it is possible. “That there is light at the end of the tunnel.”
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