It’s one thing to hear or read about evolution, and quite another thing to actually watch it in action. In fact, it’s pretty much impossible to do since by definition evolution occurs over generations, not a single lifetime. But a powerful new video from the Harvard Medical School lets us do just that: Watch bacteria as they evolve and move across a 4 foot long petri dish — it looks like a mini-football field — through increasing concentrations of an antibiotic that would ordinarily kill them. (Here is the full report from the Harvard Gazette.)
So why aren’t the bacteria killed by the drug? Because each time the bugs reach a higher concentration of antibiotic they stop, change their DNA (they mutate), thereby developing resistance to the drug. The mutants with the higher drug resistance reproduce and then continue their trek across the antibiotic field.
By the time they reach the middle of the field they have become resistant to 1,000 times as much antibiotic as would have killed them before their first mutation. In similar research at Harvard, bacteria developed resistance to 100,000 times as much antibiotic as would have killed them initially.
The real-world experiment took place over 11 days. The time-lapse video captures the whole process in 2 minutes.
There’s a few things to notice. When bacteria evolve they don’t remain stationary, they spread: here they moved a distance of 2 feet as they developed their drug resistance. Second, the bacteria continue to press forward in the direction of the drug that should kill them, rather than sitting still or heading to safer territory. It’s almost as if they want a fight! And third, the experiment shows us how easily bacteria evolve mutations that are resistant to extremely high concentrations of an antibiotic in just a short period of time.
It is because bacteria spread and mutate so easily — that is who they are — that the UN General Assembly has convened a one-day high-level meeting on Antimicrobial Resistance this-coming September 21 at the UN Headquarters in New York. Since seeing is believing, if the UN hasn’t seen the film we hope that someone brings this remarkable work to their attention.