Antibiotic resistance is one of the scariest challenges of our time. Just this week, researchers discovered one in four samples from supermarket chickens in the UK contained antibiotic-resistant E. coli. Meanwhile, fears of drug-resistant “superbugs” continue to wrangle fears.
But more often than not, it's hard to imagine how quickly this process can occur. So to demonstrate this, researchers from Harvard Medical School and Technion-Israel Institute of Technology have created a time-lapse video that clearly shows how rapidly and effectively bacteria can evolve to gain resistance to drugs. The project is part of a new study published in Science.
The team started by making essentially a massive square petri-dish, called the “microbial evolution growth arena plate” (MEGA) and introduced the ever-present bacterium E. coli to each end. They painted bands of antibiotics at periodic strips across the MEGA, which were dosed with increasingly higher concentrations as they moved inwards. The commonly prescribed trimethoprim and ciprofloxacin were the antibiotics of choice.
It’s essentially evolution in action, all visible to the naked eye. Technion-Israel Institute of Technology/Havard Medical School/YouTube
You can see, in this gif and the video below, the bacteria march forward and hit a level of antibiotics. The vast majority are stopped in their tracks and killed off by the drug. However, a pocket full of drug-resistant mutants slip through. These mutants continue to survive and thrive until they reach the next band of even stronger antibiotics, and the same process occurs. Eventually, after 12 days, the bacteria managed to pass the final band of 1000x strength antibiotics.
Interestingly, it also broke a common assumption that the bacteria that survive the highest concentration of antibiotics are the most resistant.
“What we saw suggests that evolution is not always led by the most resistant mutants,” Michael Baym, the study’s lead author from Harvard, said in a statement. “Sometimes it favors the first to get there. The strongest mutants are, in fact, often moving behind more vulnerable strains. Who gets there first may be predicated on proximity rather than mutation strength.”
Tami Lieberman, who also worked on the project, added: "This is a stunning demonstration of how quickly microbes evolve. When shown the video, evolutionary biologists immediately recognize concepts they’ve thought about in the abstract, while nonspecialists immediately begin to ask really good questions."
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