00:00There's something creepy hiding in your saliva. Yes, right in your mouth.
00:05Picture a microscopic vampire that doesn't sparkle. Instead, it steals nutrients that wouldn't move out.
00:11The unsettling part is that this vampire microbe seems to be linked to gum disease, cystic fibrosis, and even antibiotic
00:18resistance.
00:20Not bad for something you'd need a powerful microscope just to see.
00:24Researchers in the U.S. found a brand new life form, an ultra-small bacterium that can't survive on its
00:30own.
00:31It clings to other bacteria and drains them to stay alive.
00:35This thing is unnervingly simple. It has only about 700 genes, which is almost nothing in biological terms.
00:43And since it's missing so much basic machinery, it can't even make building blocks for life.
00:49So, it feeds off another bacterium instead.
00:54Interestingly, scientists didn't even find it on purpose.
00:57They kept spotting a weird piece of genetic code in saliva samples that didn't match anything we knew.
01:03Other labs had seen the same mystery code before, but no one could figure out where it came from.
01:09But eventually, researchers cracked this mystery.
01:12The code belonged to a tiny bacterium hunting down a common mouth bacterium called actinomyces.
01:18The newly discovered organism sticks to its outer surface and feeds off it, like a real parasite.
01:26Scientists have already seen bacteria infect other bacteria before.
01:31But this is the first one ever found that's completely dependent on its host.
01:36If it doesn't have a host, it won't survive.
01:38That's another reason why it has stayed hidden for so long.
01:42You can't grow it in a lab unless its bacterial victim is there too.
01:47Now, how does it all work?
01:50At first, the host bacterium can fight back.
01:53It puts up with these tiny parasites while they suck nutrients out of it.
01:57But over time, it gets weaker and, eventually, it loses.
02:03Scientists still don't fully understand how this new vampire bacterium makes copies of itself
02:09or how it jumps from one bacterial victim to the next.
02:12But one thing really got their attention.
02:15When they looked at people with gum disease and cystic fibrosis,
02:19they found a lot of this parasite's DNA way more than normal.
02:23We already knew that actinomyces plays a role in gum disease.
02:28But when this parasite shows up, things get worse.
02:32The infected bacteria became better at dodging white blood cells,
02:36which means your immune system has a harder time doing its job.
02:40The researchers also found that the host bacteria became more resistant to antibiotics.
02:46So now it's harder to get rid of them, even with medicine.
02:50The team wants to dig deeper into this creepy symbiosis.
02:55They're trying to figure out exactly how this parasite bacterium affects human health.
02:59Hopefully, once we understand it, it'll help doctors treat infections better.
03:04Even then, saliva won't stop surprising us, because it might actually be venomous.
03:10Before we dive into this shocking claim, a quick saliva reality check.
03:16So, spit does way more than just show up when you smell pizza.
03:20First off, saliva heals wounds fast.
03:24Have you ever noticed that a cut inside your mouth disappears way quicker than one on your arm?
03:29Saliva contains a protein called histatin, which helps get rid of bacteria.
03:34So when you bite your cheek or burn your tongue, saliva jumps in and speeds up healing.
03:39It's like your mouth has its own built-in first aid kit.
03:44Now, here's a kind of gross fact.
03:46You make a lot of saliva.
03:49On average, adults produce about 20 ounces a day.
03:54And it's not constant.
03:56You make more when you see, smell, or even think about food.
03:59And you produce less when you're asleep, dehydrated, nervous, or anxious.
04:04Add it all up over a year, and your mouth makes enough saliva to fill about two bathtubs.
04:11Congrats, I guess.
04:13Also, salivary stones are a real thing.
04:17They're just like kidney stones, but in your mouth.
04:20If calcium builds up in the tiny tube that transports saliva from your gland to your mouth,
04:25it can harden into a stone and block the flow.
04:29This happens more often in men and varies a lot from person to person.
04:33Some people just hold on to more minerals than others.
04:36Small stones can sometimes pass on their own, especially if you drink water, apply warm pressure,
04:42take anti-inflammatories, or even suck on a lemon to get saliva flowing.
04:47But bigger ones might need a medical procedure to break them up.
04:52Next, saliva is your main defense against cavities.
04:56Every time you eat, especially sweets, saliva helps sweep away food bits and sugar
05:01before bacteria can start eating through your teeth.
05:05Without saliva, all that stuff would just sit there, break down, and slowly rot your teeth.
05:11And finally, you need saliva to taste food.
05:15Taste buds can't do their job unless food molecules are first dissolved in saliva.
05:21Without saliva, everything would taste like cardboard.
05:24And now, what if I told you humans are going to become venomous one day?
05:29Would you believe me?
05:31Probably not, and for good reason.
05:33This won't happen, at least not anytime soon.
05:36But the creepy twist is that we do have the parts needed to make venom.
05:42New research shows that humans, along with all mammals and reptiles, have a shared genetic mechanism
05:48that can be used to produce venom.
05:50It's mostly linked to our salivary glands.
05:53So, yes, spit again.
05:57Scientists think this could explain how venom has popped up again and again in evolution,
06:01more than 100 separate times.
06:04Even in animals that started out totally harmless.
06:08One of the researchers put it like this.
06:10We've already got all the building blocks.
06:13Evolution just hasn't flipped the switch for us yet.
06:16Venom in the mouth isn't rare in the animal world, by the way.
06:19Spiders have it.
06:21Snakes have it, too.
06:22Even the slow loris, which is the only venomous primate, has it.
06:26And in every case, those venom glands started out as regular salivary glands, just like ours.
06:33Scientists knew that before, but this study finally explains how spit turns into poison at the molecular level.
06:39Venom seems to be one of nature's favorite reusable weapons.
06:44Different animals have totally different lifestyles and still use surprisingly similar venom parts.
06:50For example, some centipede venom ingredients also show up in snake venom.
06:54Now, instead of looking at the toxins themselves, which change fast and get more and more complicated,
07:01researchers focused on the support system behind venom.
07:04I mean those behind-the-scenes genes that don't make poison directly, but kind of run the whole operation.
07:11We can think of them as factory workers.
07:14The scientists started with a well-studied pit viper and looked at which genes were linked to its venom system.
07:20And they found something unexpected.
07:23The same group of genes showed up all over the body in reptiles, birds, and mammals, including humans.
07:30Many of those genes help fold proteins correctly,
07:34which matters a lot when an animal is pumping out large amounts of venom.
07:38Human salivary glands are packed with the same types of genes.
07:42Saliva already makes tons of proteins, so the basic setup for venom is kind of already there.
07:48We even make a protein called calicrine, which shows up in many venom systems.
07:54It's tough, flexible, and keeps working even when it mutates, which makes it perfect for evolution to mess with.
08:02One thing it does is drop blood pressure fast, which is not great when you're on the receiving end.
08:08The whole mechanism can actually explain why venom has evolved so many times.
08:13Evolution tweaks what's already available and tailors it to an animal's lifestyle.
08:20Some snakes use venom that shuts down the nervous system instantly.
08:23Others use venom that slowly crashes the circulatory system.
08:28The same species living in different environments use different venom recipes.
08:33A few mammals do use venom today.
08:36Vampire bats use toxic saliva to keep blood flowing while they feed.
08:41Shrews use venom to take down prey bigger than they should be able to handle.
08:46Platypuses use venom to fight rivals.
08:48But at the moment, humans don't need any of this.
08:52We have all the necessary tools to protect ourselves, and venom is expensive to make.
08:57It takes energy.
08:59So when animals stop needing it, evolution often gets rid of it.
09:03For example, some sea snakes still have leftover venom glands, but don't use them anymore because their diet has changed.
09:11But how would our lives change if we were venomous?
09:14Share your ideas in the comments below.
09:17That's it for today.
09:18So hey, if you pacified your curiosity, then give the video a like and share it with your friends.
09:23Or if you want more, just click on these videos and stay on the bright side.
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