Researchers from the Harvard Medical School and the Technion-Israel Institute of Technology have come up with a way to observe bacteria as it evolves and develops antibiotic resistance.
Called the Microbial Evolution and Growth Arena (MEGA) plate, the experiment involved the construction of a 2-by-4-foot petri dish, which the researchers filled with 14 liters of agar, a jelly-like substance derived from seaweed commonly utilized in labs to provide nourishment for organisms to grow.
The petri dish was then split into nine sections, with the outermost portion free from drugs and the center with the highest concentration of antibiotics: 1,000 times more compared with the section with the lowest dose. From the outside going in, antibiotic levels featured a tenfold increase in dose.
With a camera mounted over the MEGA petri dish, the researchers observed as the bacterium Escherichia coli (E. coli) adapted to higher doses of antibiotics. The experiment was carried out over a course of two weeks and is believed to be the first large-scale look at how bacteria move and adapt to survive, and even thrive, in the presence of antibiotics.
"It's also a powerful illustration of how easy it is for bacteria to become resistant to antibiotics," said Roy Kishony, senior investigator for the study published in the journal Science.
The researchers know quite a bit about bacterial internal defense mechanisms used in evading antibiotics, but there is little known about how bacteria physically move while adapting to different environments. And while the experiment gave a clear look at how bacterial evolution occurs, they warn against assuming that the movement they recorded perfectly matches bacterial activity in hospital and real-world settings.
Aside from offering a cinematic way of viewing evolution, the MEGA plate experiment offered a few key insights about bacterial behavior, like initial growth rates slow down to give way to mutations, that the most resistant bacteria are not always the fastest movers and those that survive the highest concentration of antibiotic are not always the most resistant.
According to Michael Baym, first author of the study, what they observed with the MEGA experiment suggests that the most resistant mutants don't always lead the evolution. Sometimes, it's a matter of who gets there first, and sometimes that's dictated by proximity and not mutation strength.
Antibiotic resistance remains a big problem so understanding how bacteria physically move in the presence of drugs can be an important contribution to the fight. According to a report, if antimicrobial resistance is not mitigated now, it can lead to deaths every three seconds due to drug-resistant bacteria by 2050. That's 10 million people dead and global losses amounting to $100 trillion each year.
Watch the bacteria in action below!
Photo: NIAID | Flickr
