If seeing is believing, then it doesn’t get better than this! The time-lapse they made with these snaps is a powerful display of evolution at work – and a bone-chilling reminder of just how flimsy our drugs are against pathogens.
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The experiment consisted of placing the bacterium Escherichia coli in a huge 2-by-4-foot petri dish filled with agar (the jelly-like material used to nurture bacterial colonies in the lab). It took 11 days for the bacterial population to evolve resistance to a lethal, thousand-fold increase in antibiotic concentration. Each band was given successively higher doses of an antibiotic, starting from 0 in the outermost bands, gradually increasing to 10 times, 100 times, up 1000 times in the middle band.
Over two weeks, a camera mounted on the ceiling above the dish took periodic snapshots that the researchers spliced into a time-lapsed montage.
Initial mutations led to slower growth-a finding that suggests bacteria adapting to the antibiotic aren’t able to grow at optimal speed while developing mutations.
The researchers have called it the “Microbial Evolution and Growth Arena”… or the very apt “MEGA” for short. In an area of the dish, scientists added the amount of drug enough to kill the bacterium, while in other parts of the plate the amount of antibiotic was not sufficient to kill it but provoked a particular response.
In a hypnotic and somewhat terrifying video, the Harvard Medical School has shown how bacteria evolve and mutate as they become impervious to drugs.
“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”, said Lieberman, a research fellow at MIT. Whenever the colony encounters a higher concentration of antibiotic, it pauses.
Researchers found that bacteria continued to grow until they reached the antibiotic dose that was too strong for them to survive and spread.
But then a small group of bacteria, containing a mutation that allows them to survive the chemical assault, break through. Resistance occurred through the successive accumulation of genetic changes. This goes against the commonly held belief that only the most resistant mutants survive high concentrations of a drug.
In a creative stroke inspired by Hollywood wizardry, scientists from Harvard Medical School and Technion-Israel Institute of Technology have designed a simple way to observe how bacteria move as they become impervious to drugs.
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In the relatively short timeframe that we’ve been affected by harmful bacteria, they’ve shown resistance to almost all of the antibiotics we’ve thrown at them, and with the CDC estimating that 23,000 people die each year due to antibiotic resistant infections, this is a huge issue. In the span of just 10 days, bacteria were able to produce mutant strains that were capable of overcoming even 1,000 times higher dosage of antibiotic.
