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Like every rose has its thorn, the fangblenny is an adorable fish with sharp fangs and potent venom. But scientists think we might be able to use their venom as a painkiller! Meanwhile, a killer bacterium could be a promising new antibiotic.

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Predatory bacteria

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Hank: Whether they’re talking about people or animals, looks can be deceiving. The most innocent-looking critters can pack a huge punch. Take this tiny fish.

Pretty cute, right? Or maybe it’d look like a tasty snack if you were a predator in a reef. At least, until it reveals a pair of sharp fangs in its lower jaw, which can inject a potent venom.

That’s why it’s called a fangblenny. But there’s a twist to the fangblenny’s toxic bite. It seriously messes up predators but, unlike the searing pain from something like a stingray spine, the venom probably doesn’t hurt much at all.

In fact, an international team of biologists reported this week in the journal Current Biology that one of the chemicals in the venom is more like a painkiller. So we might even be able to someday use it in medicine!

These were the first scientists to analyze fangblenny venom. And they found three types of proteins that act as toxins, none of which had ever been found in fish before. One was a special type of enzyme similar to those in bee and snake venom, which can do a lot of damage by ripping apart cell membranes. Plus, there was a neuropeptide that’s also found in cone snails, which could be acting as a neurotransmitter. And the third kind of peptide could bind to opioid receptors, and block pain, among other effects. Some scorpions use similar proteins.

Basically, the itty-bitty fangblenny evolved a venom that’s snake, snail, and scorpion venom – all rolled into one.

As for how this venom works, tests on rats showed that its main effect is to dramatically lower blood pressure, probably because of the two peptides. The scientists think this blood pressure drop could make any predators uncoordinated, or even start violently shaking... even if it’s not painful because of the opioid-like compound. That’s enough to let a fangblenny slip away without a scratch.

It’s a good enough strategy that lots of harmless fish have evolved to mimic venomous fangblennies, from their colors to their swimming styles. And humans might be able to benefit by copying the fangblenny, too. Scientists who study venoms are always on the look-out for new molecules that could be useful in medicine, and the researchers say this unique venom might be worth studying as a new type of painkiller.

If it sounds weird to look in fish venom for new drugs, some scientists are considering an even stranger prospect: using bacteria as antibiotics. Antibiotics, of course, are supposed to kill bacteria. So the idea of injecting more bacteria into your bacteria-ridden body seems... kind of bananas.

But this bacterium – called Bdellovibrio bacteriovorus, or BV for short – could help. In a paper published this week in Biophysical Journal, scientists learned more about how these assassins hunt. These bacteria might offer a new way to treat infections that are resistant to multiple drugs, or bust apart biofilms, the slimy collections of microbes that coat surfaces, like on medical equipment.

BV kills other bacteria kind of like a virus does. It squeezes inside a bacterial cell, replicates, and then all those clone babies burst out, killing the host. Because it works differently from antibiotics, which usually target specific bits around or inside bacterial cells, BV can kill bacteria even after many drugs have failed. Bacteria don’t seem to evolve ways to defend themselves against this kind of attack.

And your cells are safe, because BV can only grow inside gram-negative bacteria, like E. coli or Salmonella, which have a specific kind of cell wall surrounding them. But while we know some things about BV’s life cycle, and even have its genome sequenced, how BV finds its prey has been a mystery.

Is BV an active hunter, tracking its victims by sensing chemical signals? Or is it just bumping into them by chance? Knowing which tactic the bacteria use could be really helpful in figuring out how to use them as a treatment, whether in hospitals or human bodies.

Well, in the study from this week, scientists at Indiana University found that BV movement is random, but it has a trick for upping its chances of running into its victims. The researchers used microscopes to watch BV, along with some E. coli prey, swimming in some liquid.

That swimming is the key. The bacterium has a flagellum that propels it through water super quickly. It can cover a distance 100 times its body length in one second! All that tail-whipping makes a lot of swirling waves, which makes BV swim in circles and zero in on surfaces, or other obstacles – in this case, microbeads the researchers added.

And those surfaces were also the regions with the most E. coli. E. coli is bigger and slower, but also gets trapped in the same places because of the way it swims. So, even though BV doesn’t use any chemical or electrical signals to know what it’s doing, it still ends up where other bacteria are likely to be. It’s possible scientists could engineer the bacterium to be even more sensitive and zero in on surfaces faster, which could make it even an more efficient antibiotic.

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