First vision of bacteria harpooning DNA to accelerate evolution

Bacteria evolve fast – and that could be bad news for those of us who don't want to see easily-treatable diseases make a roaring comeback. Resistance to antibiotics is a growing concern, but if scientists can see how the microbes evolve, they might be able to intervene. 

Now researchers at Indiana University have peeked into that tiny world, producing the first direct images of bacteria extending "harpoons" to snare and absorb bits of DNA.

One of the main ways bacteria evolve new traits is through DNA uptake, otherwise known as horizontal gene transfer. This process allows them to latch onto fragments of DNA from their surroundings and incorporate it into their own genome, teaching themselves new tricks such as antibiotic resistance. Bacteria can then share these snippets with each other, spreading the ability throughout the population.

"Horizontal gene transfer is an important way that antibiotic resistance moves between bacterial species, but the process has never been observed before, since the structures involved are so incredibly small," says Ankur Dalia, senior author of the study. "It's important to understand this process, since the more we understand about how bacteria share DNA, the better our chances are of thwarting it."

While past research has focused on blocking bacteria from sharing these DNA fragments, the new study looked to find ways to potentially prevent them from absorbing them in the first place. It's long been known that bacteria use extendable appendages known as pili to help them gather DNA from around them, but direct evidence showing this mechanism has eluded scientists until now.