The experiment (and video) shows bacterium Escherichia Coli adapting to increasingly higher doses of antibiotics on a dish divided into sections saturated with various doses of medication. Mutations to the antibiotic medium resulted in initial growth slowdown. New territory growth was lead by the strains that were sufficiently strong and close to the antibiotic frontier, rather than simply by the strongest strains which often lagged behind.
The Atlantic and other publications presented this study as Evolution in Action (as in Darwinian Evolution). However, a number of questions arise that might invalidate this claim:
- Did the original bacteria population have a common ancestor? If not, there is no baseline to compare the adapting bacteria against.
- How different were the adapted bacteria from the initial ones? Were they still Escherichia Coli? If so, where exactly does Adaptation turn into Evolution? “Speciation” is supposed to mark the transition, but without a clear definition of a “species” (particularly when it comes to asexual reproduction as in this case), and without a solid baseline, the transition remains elusive.
- What caused the resistant bacteria to temporarily grow slower? Did these strains have to trade off other features for antibiotic resistance, or were they better off (more “fit”) overall?
- What are the limits of antibiotic resistance? To what extent can these bacteria also build resistance against cleaning chemicals?
- What happens with the resistant bacteria population if the bactericide is removed? Do the various resistant strains turn into a homogenous population? Does that population retain its antibiotic resistance?
- How well do the results match when the experiment is replicated with another bacteria strain? Do the resistant bacteria from the two strains have the same adaptation?
Most of the questions above can be easily answered with simple follow-up studies. Until then, the story is incomplete, and the “Evolution in Action” claim remains unsubstantiated. More importantly, the study of antibiotic resistance is vital to modern medicine and deserves more thorough research.
Links:
https://www.aaas.org/news/scientists-build-giant-petri-dish-film-bacteria-resistance
http://www.theatlantic.com/science/archive/2016/09/stunning-videos-of-evolution-in-action/499136/