With the help of a giant Petri dish, Israeli and American researchers are showing us evolution at its most ferocious.
The time-lapse video above shows the first large-scale glimpse of how bacteria (in this case E. coli) mutate into superbugs when faced with increasing doses of antibiotics, to become 1000 times more resistant than their original state.
A giant Petri dish
Seeking to better visualize how bacteria transform when treated with different types of antibiotics, Israeli and American researchers designed a simple experiment. Led by Professor Roy Kishony of Harvard Medical School (HMS) and the Technion-Israel Institute of Technology, and documented in the September 9th issue of Science, a team of researchers constructed a two-by-four foot Petri dish, dubbed the “MEGA-plate”, and filled it with 14 liters of agar, a seaweed-derived jellylike substance commonly used in labs to nourish organisms as they grow. The dish was split into different sections, with each portion receiving varying doses of antibiotics.
The bacteria on the outermost part of the dish were not treated with any drugs at all, while the next portion had just the right amount of antibiotics to kill the bug. Each following section was given a dose ten times more powerful than the last, with the center portion getting a thousand times more antibiotics than the areas with the lowest dosage. In order to track how the E. coli developed, the researchers attached a camera to the facility’s ceiling, taking photos of the evolution over a span of two weeks.
Findings: Mutant superbugs
According to their findings, when faced with antibiotics, at first most of the bacteria perished, but there was always a small percentage of mutant bacteria that adjusted to the antibiotics and were able to survive. What happened then was a form of competition between mutated strains, as each sought to move on to parts of the dish that had higher doses of antibiotics. Most importantly, the experiment showed that the most resistant of the mutants proved to be capable of resisting the highest dose of antibiotics, effectively making them E. coli superbugs.
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Superbugs have been identified by the World Health Organisation as one of the greatest threats to human health after adapting to become resistant to all forms of antibiotics. Each year across the globe more than 700,000 people die, including about 214,000 infants less than a month old, due to antibiotic-resistant bacteria.
Aside from being a strong visualization of evolution, and its role in the rise of superbugs, the experiment gives biologists a tool to better analyze how those superbugs develop.
Inspired by Hollywood
The inspiration for the experiment ultimately came from a Hollywood movie. Seeking a visually captivating way to teach evolution to students in a graduate course, Kishony drew upon an idea from a digital billboard he saw advertising the 2011 film ‘Contagion’, about a deadly viral pandemic. As a marketing tool, the producers of the film created a giant lab dish showing swarms of painted, glowing microbes creeping slowly across a dark backdrop to spell out the title of the movie.
“We really did not invent the MEGA-plate,” Kishony explained in an interview. “It was invented in Hollywood, of all places.”
Given the circumstances, this may be a case of life imitating art.
Photos and Videos: Technion, Harvard Medical School