A new study in Nature Genetics sheds light on exactly how bacteria evolved to resist drugs, according to the New Scientist. Harvard University's Erdal Toprak, Adrian Veres, and their colleagues have developed a device they call a "morbidostat," which monitors the growth of bacteria as they are exposed to increasing doses of antibiotics. The researchers used the device to measure how a strain of E. coli responded to three different drugs over the course of 25 days. They found that while resistance increased for all three drugs, resistance to chloramphenicol and doxycycline emerged continuously over time, while resistance to trimethoprim developed discretely, New Scientist says. "The team sequenced the genome of E. coli from the final stage of the experiment," the article adds. "Bacteria resistant to chloramphenicol and doxycycline had a large number of changes all over their genome, suggesting that lots of small mutations outsmart the drugs. For trimethoprim resistance, most changes took place in just one gene."
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