A time-lapsed video of E. coli bacteria developing resistance to increasingly higher doses of antibiotics over 10 days. Video courtesy: Kishony Lab/Harvard Medical School and Technion
It’s spreading! Scientists at Harvard Medical School in Boston and Technion-Israel have designed a way to document bacteria as the microbes become impervious to antibiotics. The experiments provide the first large-scale glimpse of how these germs adapt to survive increasingly high doses of antibiotics.
To observe this phenomenon, scientists built a 2-by-4-foot petri dish and filled it with agar, a jelly-like substance that nourishes bacteria. Next, they split this agar platform into five sections and coated them with different amounts of antibiotics. The outside sections had no medicine, but the dosage increased stepwise by a factor of 10 for each inner area. The center harbored 1,000 times the minimum dose needed to kill it off.
Using a ceiling-mounted camera, the scientists created a time lapse video of the bacteria’s progress over the course of 10 days. They discovered the bacteria moved slowest while mutating, but returned to optimal growth speeds once fully resistant.
But the mutant strains were not always the fastest nor the most ambitious.
They occasionally deferred, allowing weaker strains to be the first to carve into the front lines and the higher amounts of antibiotic.
The mutated bacteria are antibiotic resistant, but the study suggests they aren’t the fittest or the best at multiplying. This title goes to the microbes at the leading edge that first attempt to resist the antibiotic.
“What we saw suggests that evolution is not always led by the most resistant mutants,” said study first author Michael Baym, a research fellow in systems biology at Harvard Medical School. “Sometimes it favors the first to get there. The strongest mutants are, in fact, often moving behind more vulnerable strains.”
See below for a recap of NewsHour’s twitter narrative on the team’s #bacteria research:
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