CRISPR Pill May Be Key in Fight Against Antibiotic Resistance

Not an alien world, but an immune system. Artist's rendition of Cas9 enveloping DNA strands that are about the get chopped. Source: http://www.publico.es/

Quick dispatch from the world of CRISPR.

And no, I don't mean that drawer in your fridge ;p

CRISPR-Cas9 is the gee-whiz gene-editing tool that's taken the world by storm. Compared to previous methods, it's *relatively* easy to use and has an impressive success rate. (Although CRISPR is often touted as the democratization of genetic engineering, as one journalist found out, it's not exactly as plug-and-play as people might think.)

That said, CRISPR and its newer generations are poised to overhaul gene therapy. But today I want to talk about another function of CRISPR, one that returns the technique to its roots: a swallowable CRISPR pill, that activates along the gut and convinces resistant infectious microbes to shred their DNA to bits.

Yes, I'm talking about a CRISPR-based antibiotic.

To get to how a gene editing tool can also be used to kill microbes, we need to first take a deeper look at CRISPR's origin: a part of the bacteria’s immune defense system. This might be surprising, but bacteria are constantly under attack by a type of virus called phages. Just like our own bodies learn to recognize infectious particles and generate antibodies towards them, the bacteria snips a bit of the invading phage's genes and sticks it into their own genome, making a "molecular memory" of the phage.

The little bubble-headed creatures sitting on that giant sun-like bacteria? Phages. They're the creepiest cutest things ever. You can see some of them injecting their DNA (or RNA) into the bacteria, like skinny blue poops.

This way, when the bacteria detects a matching viral DNA sequence, they activate CRISPR. Along with a pair of protein scissors Cas9, the team hunts down and chops up the invading viral DNA.

A few years ago researchers found that if they turned CRISPR on the bacteria's own genome, the result is lethal (think of it kind of as an autoimmune disease for the bacteria). This gave the scientists a brilliant idea: what if we make a phage that contains part of the bad bacteria's genome sequence (say, salmonella) and have it infect the disease-causing bacteria?

In this way, only the bad bacteria will activate CRISPR and shred their own genomes (and themselves in the process, goodbye salmonella), while our healthy gut bacteria as spared.

Because the Trojan phage works very differently than all the antibiotics we currently have, it could help slow the terrifying antibiotic resistance problem that's increasingly plaguing the medical community.

I hate preaching about antibiotic resistance and what it could mean for civilization (end it!). So I'll let the video below do the talking: a lab recorded a strain of bacteria become impervious to increasingly higher doses of an antibiotic—up to 1,000 times higher—in just 11 days. Now picture that running rouge among us - yikes!

For more about CRISPR as an antibiotic, head over to Singularity Hub.

If you'd like to learn more about CRISPR as a gene-editing tool, RadioLab has an (as always) excellent podcast episode about it here.