Antibiotics are powerful drugs used to treat bacterial infections. Recently, however, a growing number of bacterial infections have developed resistance to many commonly used antibiotics. In fact, the World Health Organization has pegged antibiotic resistance as one of the world’s biggest threats to global health! Bacteria acquire antibiotic resistance by changing in a way that reduces drug effectiveness.
In a recent article, a research team at Harvard and the Technion-Israel Institute of Technology introduced a new device that allows antibiotic-resistance evolution to be watched like a movie. The device, called the “microbial evolution growth arena plate” (MEGA plate), is a giant rectangular petri dish with stripes of increasingly high antibiotic concentrations. Bacteria start in the lowest antibiotic stripe and quickly run out of room to expand; the only way to keep growing is to mutate in such a way that they can access the untouched, but higher antibiotic, stripes of the dish. Surprisingly, scientists observed that bacteria were able to colonize even the highest concentration stripes (1000x as much antibiotic) in as little as 11 days.
Adam Waite, a Postdoctoral Associate at Yale University, highlights the importance of MEGA, writing, ‘MEGA is important because it provides the large population sizes and number of generations while maintaining spatial structure.’ Large numbers of bacteria make this experiment possible, by increasing the number of chances to see a mutant with higher resistance emerge; further, the layout of the plate makes it easy to look backwards through evolutionary time to track the mutations that make for successful resistance strains. Moving forward Julia Schwartzman, a Postdoctoral Fellow at Harvard, predicts: ‘Future experiments using different types of selection on the MEGA plates might provide a tractable model with which to study evolution in structured environments.’
Managing Correspondent: Alexandra Schnell
Acknowledgments: Many thanks to Adam Waite, a Postdoctoral Associate in the Department of Molecular, Cellular, and Developmental Biology, and Julia Schwartzman, a Postdoctoral Fellow at Harvard University, for helpful discussions and comments.
Original Article: Baym, Michael, Tami D. Lieberman, Eric D. Kelsic, Remy Chait, Rotem Gross, Idan Yelin, and Roy Kishony. “Spatiotemporal microbial evolution on antibiotic landscapes.” Science 353, no. 6304 (2016): 1147-1151.