Scientists spy on superbugs to see how they outsmart our antibiotics
Scientists have discovered yet another way that singlecelled organisms have outsmarted us.
The tiny bacteria that live inside our guts have an ingenious way of withstanding the onslaught of antibiotics we throw at them, according to a report published Thursday in the journal Science. The twopart system allows bacterial cells to stay alive until another bacterium can deliver a lifeline, packaged in a snippet of DNA.
Microbes 1, Humans 0. “I’m afraid our findings are great news for bacterial cells — not so good for us,” said study leader Christian Lesterlin, a researcher in the Molecular Microbiology and Structural Biochemistry program at Universite Lyon in France.
Lesterlin and his colleagues already knew that superbugs could repel even our most modern medicines. What they didn’t know was how they managed to pull it off.
“These are amazing abilities they have, to be able to adapt and survive in harsh environments with antibiotics,” he said. “But the more we understand about it, the more we can do for human health.”
For most of human history, bacteria have had their way with us. Though some of them are helpful, others cause dangerous diseases like pneumonia, cholera and meningitis. The bacterium Yersinia pestis wiped out roughly 20% of the world’s population in the mid1300s during the pandemic known as the Black Death.
When scientists first developed antibiotics in the early 1900s, humans enjoyed the upper hand — for a while. Some of the drugs target the machinery that maintains a bacterium’s all-important cell wall. Others rob bacteria of the proteins they need to carry out essential functions or damage the DNA needed to reproduce.
It took just a few decades for the first drug-resistant strains to appear. Since then, the invention of each new antibiotic invited a jeering reply.
Doctors responded by prescribing another antibiotic drug, and another. Then two drugs together. Then three. But now the arsenal is all but depleted, and there are strains of Escherichia coli, Klebsiella pneumoniae, acinetobacter and enterococcus that have evolved to overcome almost every medicine thrown at them.
So scientists are racing to understand superbugs’ tactics. Among the most urgent questions is this: How does antibiotic resistance spread between bacteria cells, even — or especially — in the presence of antibiotics that are designed to knock them back?
Bacteria know better than to wait around for a random mutation in their DNA that will protect them from antibiotics. Those mutations will come but not often: For some drugs, only about 1 in 10,000 bacteria will develop resistance that way. For other drugs, only about one in a billion will do so. Either way, that’s not very efficient.
Luckily for bacteria, they have plasmids at their disposal. These are circular snippets of DNA, and they can include genes that carry instructions for repelling specific antibiotics. Bacteria can swap useful plasmids with one another while socializing together in the human gut.
(Imagine having an anti-cancer gene and being able to pass out copies of it to everybody you bump into at the grocery store. Like I said, bacteria have outsmarted us.)