What did that bacterium say?


Full Transcript

Announcer: Welcome to Stuff from the Science Lab from howstuffworks.com.

Allison Loudermilk: Hey, guys, and welcome to the podcast. This is Allison Loudermilk, the science editor at howstuffworks.com.

Robert Lamb: And this is Robert Lamb, science writer at howstuffworks.com.

Allison Loudermilk: So, Robert.

Robert Lamb: Yeah?

Allison Loudermilk: Have you ever thrown a party?

Robert Lamb: I have certainly helped throw some parties, yeah. When I first moved to Atlanta, I lived in this house with two other people and it was -

Allison Loudermilk: Was it a party house?

Robert Lamb: Yeah, it was kind of a party house.

Allison Loudermilk: Really? Tell me about it.

Robert Lamb: Well, it was in a nice neighborhood in Atlanta, but it was the one house on the street that wasn't that well kept up. It didn't have a nice family living in it.

Allison Loudermilk: The neighbors would cross the street when they were walking their dogs?

Robert Lamb: Yeah, every street has that one house, and this was that one house. It was just because the dude who owned it was too lazy to fix it up and sell it. So he was like, "I can just rent it out by the month to these people." So for years, everybody who lived in it knew people who had lived in it before. And it just continually amassed more and more used Tupperware and kitchen items in the pantry.

Allison Loudermilk: And none of the Tupperware had tops.

Robert Lamb: There were tops in there, but god bless anybody who actually line anything up and reuse it. But we'd have parties. And like we were saying, first it's the people getting ready for the party. And then the people who annoyingly show up early to attend the party, but don't want to actually help you set up.

Allison Loudermilk: "Hey, man. Can I get a beer?"

Robert Lamb: Yeah, they're asking for a drink or they're eating snacks while you're still setting up the snacks. And you're like, "What are you doing?" So then more people show up and you start cranking the music a little.

Allison Loudermilk: The party builds momentum. But when that first guy or gal comes, you don't want to put everything out right away. You don't want to put your best hors devours that you slaved over. You don't want to put out the micro brew that you're keeping for a little bit later.

Robert Lamb: Or be like, "All right. Let's dance. There's three of us here." No.

Allison Loudermilk: Yeah, you've got to save the good music for a little later when the party achieves that tipping point, that point at which the person starts doing the worm on the floor. Somebody retires to a corner to do a little cozying up to one another.

Robert Lamb: The guy falls off the roof.

Allison Loudermilk: No, no, no.

Robert Lamb: No, that happened at this house.

Allison Loudermilk: Are you serious?

Robert Lamb: Yeah, some dude climbed up on the roof and fell off. He was fine, because the kind of person who crawls up on the top of a roof and falls off during the course of a party tends to be fine afterwards because he's probably done it before. But that kind of thing happens.

Allison Loudermilk: Right. So today, we're talking about that same sort of thing, only in bacteria. A bacteria party, if you will.

Robert Lamb: Which sounds like some sort of slanderous term you'd throw at your least favorite restaurant.

Allison Loudermilk: Right. So specifically, we're talking about quorum sensing, which is how bacteria communication. But first, a little background. So bacteria is just a simple single-celled organism. It doesn't have a nucleus. It lacks organelles, those tiny specialized organs within the cellular membrane - like a mitochondria or something like that. And your bacteria is going to probably be round, spiral, or rod-shaped. It may be gram positive or gram negative. And they're going to fall under the domain bacteria. So that's an overview of bacteria just in case you needed to jog your memory a bit.

Robert Lamb: And it's easy to fall into the trap of thinking of these as simple organisms, in the sense that they evolve to a point and just stop. Or it's like they never got out of the first or second grade. But it's more like they reached the second grade and just became awesome at being in second grade, in ways we typically don't give them credit for.

Allison Loudermilk: So they're pretty complex and clever organism. Consider this story. Back in the 1960s a couple of researcher notice that bacteria known as vibrio fischeri displayed more luminescence as the bacterial population grew. As you can imagine, it's hard to glow. It takes a lot of energy. So scientists determined that the bacteria were able to preserve their energy until they realized, "Hey, this is the right moment. Let's make a good glow. There are enough of us here to make an impression." So a lot of time you can see that good glow in the liquid organ of a deep-sea creature, like a squid.

And it was fascinating stuff because these bacteria were living symbiotically with the squid or whatever creature they happened to inhabit. And the bioluminescent bacteria would become the light structure for the eye. It was so interesting.

Robert Lamb: So it was like if you have a giant monster that coated itself with raver kids with little glow sticks? If you get enough of them together - one raver kid with a glow stick's not going to produce a lot. But if you get a lot of them together - except these things end up gathering together and then they produce more glowing.

Allison Loudermilk: Right, like the raver kids, no doubt - and the giant squid. So the point of this is that the population has to reach a sufficient size to emanate that killer glow.

Robert Lamb: Again, like the party. You have to get a certain number of people together before the party really starts kicking as they say.

Allison Loudermilk: Yeah. And that's an example of quorum sensing. It's really just how bacteria communicate. It's usually used to tell other bacteria, "Hey, there are enough of us here now. Let's get on to bacterial business." And there's some other organisms capable of mimicking quorum sensing. Like I saw some research on plants, algae, and insects too - like honeybees. I guess insects might use it to figure out where they're going to plant their next colony. So the name, as you can imagine, comes from quorum, or just the majority of people from some particular group that you need to achieve for a vote or political action to occur.

Robert Lamb: You're always hearing it on the news, "They'll have to get a quorum on a particular topic before this legislation can pass or this rule can be passed up in a company."

Allison Loudermilk: Example, howstuffworks.com couldn't pass that sweet new motion for a four-day workweek because a quorum wasn't achieved.

Robert Lamb: I didn't get the email on that one.

Allison Loudermilk: I know. Neither did I. If only it had gone out.

Robert Lamb: I don't know, because then you're going to have 10-hour workdays, right?

Allison Loudermilk: I guess you could bump it up. What do the French people do?

Robert Lamb: Well, that's a whole other issue.

Allison Loudermilk: So let's talk about quorum sensing, how bacteria reach that critical capacity to communicate. So the mechanism here that you're going to want to concentrate on is auto inducers. Bacteria produce and they give off these auto inducers. And they function as signaling molecules, like pheromones. So the concentration of auto inducers in any given area is going to correspond with the size of the bacterial population.

Robert Lamb: Like to bring this to a party. You know how when people come to a party, they never stick with just one cup for their beverage, they end up leaving several around laying on coffee tables and bookshelves.

Allison Loudermilk: I see. So number of cups laying around as an indicator of how good the party is.

Robert Lamb: Right. If you have 200 cups laying around, that means you have 50 people there.

Allison Loudermilk: So similarly, a high concentration of auto inducers is going to tell you that a lot of bacteria are present. So once you get enough bacteria coming to the party, they're going to start producing the molecules that are so toxic to their host. They may even form a biofilm, which is just a massive group of bacteria that may form a coating on a mossy rock. You were talking about in a dog bowl.

Robert Lamb: Yeah, or if you feel a film on your teeth.

Allison Loudermilk: Or a medical device. They're pretty common on a medical device like a catheter, prosthetic device, or heart implant valve.

Robert Lamb: So this is the tipping point. This is the point when the party gets off the chain as they say, when the guy falls off the roof.

Allison Loudermilk: I love that you're so full of these party expression.

Robert Lamb: This is when things start happening, and that's the issue here. What happens when the bacteria actually form a quorum and start doing the dangerous things that bacteria do.

Allison Loudermilk: Right. So this would be when they mobilize, they decide to start infecting the host, generally speaking.

Robert Lamb: Right. That being the prime thing we're interested in - the dangerous stuff.

Allison Loudermilk: So just to remind you, a quorum sensing drug would stop the communication, whereas a regular antibiotic kills bacteria or stops the targeted bacteria from growing, of course allowing the development of resistant mutant bacteria.

Robert Lamb: Yeah, basically we're talking about cutting off the communication. There'll be however many bacteria getting into a room, but they don't really know all the other guys are there. There's not enough communication to get the party started. It's like if you try to have a party with a bunch of lame people. They're standing around -

Allison Loudermilk: My husband has a name for this. He calls it a lights-on sit down party, which I think is pretty apropos.

Robert Lamb: Well, if there are board games.

Allison Loudermilk: That's true.

Robert Lamb: Sometimes just Scrabble is a good level of off the chain.

Allison Loudermilk: Yeah. Indeed, Robert.

Robert Lamb: Especially if you allow creative spelling. Then it's, "Whoa. Crazy."

Allison Loudermilk: And here's something else. Bacteria don't just communicate with their own kind. They don't just communicate with the people at the party. They may have receptors for species-specific auto inducers as well as receptors for signals sent out by all other kinds of bacteria.

Robert Lamb: So there could be party crashers in the bacteria community?

Allison Loudermilk: Indeed. So in the case of our bioluminescent ones that not just the bioluminescent ones are communicating! They may be communicating with other bacteria that are just floating in the seawater chatting it up. So why does it matter? Why do we care if bacteria are communicating? It really never hurts to have new tricks up our sleeve when we're dealing with bacteria.

Robert Lamb: Yeah. And again, the key thing here is when bacteria form a quorum, a lot of times they're going to do something deadly - or at least unhealthy to the host.

Allison Loudermilk: So let's take it in the hospital. There's a pretty common bacteria called pseudomonas aeruginosa. You're smiling because you want to make a food joke about how that's -

Robert Lamb: No, I did that last week.

Allison Loudermilk: Okay. Right. So pseudomonas aeruginosa is a gram negative bacterium behind an infection that strikes and often kills people with cystic fibrosis and other immunocompromised people. This is going to be AIDS patients, people receiving chemotherapy, or people with burns. Again, it's really common in hospitals, but it doesn't affect healthy people. So a couple of scientists from the University at Buffalo were able to inhibit the master regulatory gene behind quorum sensing. So that's effectively how we are stopping bacteria from communicating, by regulating gene expression - to get into the mechanics of it.

So these scientists were able to do that. And it's cool when you consider that a lot of strains of P-aeruginosa are resistant to antibiotics. So it comes back to having more than one way to skin a cat or stop the bacteria from chatting with one another - in this case, immobilize.

Robert Lamb: And another thing I thought was cool, is an idea that was put forth by the Albert Einstein College of Medicine, and that's that these could be "everlasting antibiotics." The principle here is that we've all heard about antibiotic resistant drugs and antibiotic resistant bacteria, illness, etcetera. The idea is that by pulling out antibiotics, we're pushing against them and they're going to push back. They're going to evolve a resistance to something. And suddenly, you have to change your offense to meet their defense. But by creating a anti-quorum sensing drug, you're messing with their communication. You're not pushing them, you're just breaking them up.

Allison Loudermilk: You're not sparking resistance.

Robert Lamb: So they found that in 26 successive generations of different bacterial species -

Allison Loudermilk: That 26th generation was still as sensitive as the first one was.

Robert Lamb: Yeah. They're not learning to fight back against it. Which is awesome, because it could conceivably last forever! It could be a permanent cure.

Allison Loudermilk: I feel like everlasting is a little optimistic when it comes to an organism, as long-lasting and as adaptable as bacteria have proven to be. But still, it's an intriguing concept.

Robert Lamb: It's a little boastful. But again, if you want to get picked up by the media and you want to get your study funded -

Allison Loudermilk: That is catchy.

Robert Lamb: - you just say, "Everlasting treatment for this." They're like, "Whoa, I'll fund that."

Allison Loudermilk: So are doctors using anti-quorum sensing drugs to fight bacterial infections now? That's probably what you guys are wondering.

Robert Lamb: Not really.

Allison Loudermilk: Not so much.

Robert Lamb: Except, possibly in some traditional medicine practices. There was an interesting article - what publication was that in?

Allison Loudermilk: It was in a clinical trial. On the clinical trial website, you can check out all the clinical trials they've got going on for different things in the United States. And there's a 2008 study that was investigating Azithromycin as a potential drug. And they were using it to battle pseudomonas aeruginosa of ventilator associated pneumonia. And the study did in fact make it to phase two, but it was terminated because of financial issues. So we never got a chance to see how this was going to turn out.

Robert Lamb: Yeah, the article I was thinking of was actually in Gizmodo, and it was about McAfee.

Allison Loudermilk: He of the security computer fame.

Robert Lamb: Yeah. So apparently he was like, "I've learned how to tackle computer viruses. I'm going to go after the real thing." And he's down in Belize checking in with traditional herbal practices and looking into the possibility of anti-quorum sensing drug potential in those herbal remedies.

Allison Loudermilk: Yeah, it's interesting to read. I thought that the author, Jill Johnson, had a good take on it. It's healthy to bring a little bit of skepticism to this, especially since Belize doesn't necessarily have the vetting system that we do for new drugs. So they were looking to enlist the help of quorum sensing for all sorts of stuff like ear infections, ulcers, biofilms on your teeth - I think they were looking into a mouthwash, which would be handy. I don't know how the dental hygienists would feel about that. What would they do if we didn't have biofilms on our teeth anymore?

Robert Lamb: Oh, I think we'd still figure out a way to mess up our teeth pretty bad. Have confidence in our junk food eating ability.

Allison Loudermilk: Okay, I will. So apart from what they're doing in Belize, there are some issues with developing these kind of drugs elsewhere. And some of the issues have concerned the molecules being toxic to humans, according to a related Scientific American article I was reading. In addition, they've been having some troubles developing disrupters that work against many different species of bacteria.

Robert Lamb: Like it'll only be good to cut off one type of bacteria's communication.

Allison Loudermilk: Which might be good in the case of a bacteria that's prevalent like the aforementioned pseudomonas aeruginosa.

Robert Lamb: Yeah. But it prevents you from having a general anti-quorum cure all.

Allison Loudermilk: Right.

Robert Lamb: Also, there's some issues with the shelf life, getting it to where you can actually get it out in stores and have it be an over-the-counter thing and not a harvested on the site type of deal.

Allison Loudermilk: And there's also an interesting study that came out of the University of Edinburg. And a couple of biologists there were saying, "Hold on a second here. Bacteria aren't that simple. In fact, they may not even communicate in the same way within a particular population."

Robert Lamb: And another fact comes from some research from the University of Edinburg, that bacteria - as with humans - some are better communicators than others. So if you are able to encourage more of the poor communicating bacteria -

Allison Loudermilk: This is actually beneficial.

Robert Lamb: Yeah, because the other guys can't get a word in edgewise and really get going with their quorum. It's like if you didn't want your party to get off the hook, so you invited mostly agoraphobic people that are just going to stand there looking into their drink.

Allison Loudermilk: Have a lot of social anxiety.

Robert Lamb: So that's pretty cool, and another way that you could use this to your benefit.

Allison Loudermilk: So that about wraps it up on bacteria talking with each other.

Robert Lamb: I was surprised by it. I don't think of bacteria speaking to each other or in any way communicating. I tend to, without thinking about it, view them as this very simple organism that works like a very simple machine.

Allison Loudermilk: Not the case. They have proved us wrong once again. So if you guys want to send us any of your thoughts on bacteria or bacteria communicating - or just tell us what a good communicator you are - send us an email at sciencestuff@howstuffworks.com.

Robert Lamb: I have to admit, when you first mentioned quorum sensing drugs to me, I thought it was something like out of Dune or some sci fi novel where there's a crazy sci fi drug.

Allison Loudermilk: No, not the case. You want to do listener mail?

Robert Lamb: Yeah. We actually got some awesome listener mail in just today - not only mail, but a package.

Allison Loudermilk: Yes, our very first package, which was super exciting - from Australia nonetheless.

Robert Lamb: I was worried at first. One of the reasons we received some of our fan mail from Australia was because we made some comments about there being a lot of venomous creatures there. And some people were like, "It's not really that bad." So there was dialogue back and forth on that.

Allison Loudermilk: And then there was a comment on a comment. Do you remember that? That was very exciting for us.

Robert Lamb: So at first I'm like, "Oh, my goodness. Somebody's mailed us a snake or a scorpion." But as it turned out, not. It's actually two adorable little creatures.

Allison Loudermilk: Knitted creatures. I got a Rhodesian Ridgeback with a bandana, which is so cute - a dog.

Robert Lamb: You're favorite animal. And I received a Lammergeier, the big majestic looking bird that's in The Life series that drops bones from a great height and then goes down and eats the shattered remains. So they're really cute and they came with a letter.

Allison Loudermilk: Yeah, let's read the letter.

Robert Lamb: "Hi, Allison and Robert. G'day from Australia. For hosting such and awesome podcast that makes my commute so much more bearable, I knitted you some presents. Here's a Rhodesian Ridgeback for Allison and a Lammergeier for Robert. If they behave, perhaps you might allow them to play with Katie's narwhal and Sarah's ocelot that I dispatched last month."

Allison Loudermilk: The gals from Stuff You Missed in History Class.

Robert Lamb: Yeah, those guys. "Thank you for a great show and keep up the fantastic work. Best, CeCe, Melbourne, Australia. P.S. How about a podcast on the Higgs boson? We might find it soon."

Allison Loudermilk: Excellent. Thank you very much CeCe.

Robert Lamb: Yeah, these are awesome.

Allison Loudermilk: These are really super cute.

Robert Lamb: We took a photograph of them. I'll see if I can't throw that up on the Facebook. And the Lammergeier's going to go up on the shelf next Gamra.

Allison Loudermilk: So we've received a lot of good listener email lately, so we're going to go through some of them today. I'm pretty psyched that you guys are writing in. First up is Adulah S. And he wrote in with his very first email to an HSW podcast, and we are honored. So here's what he had to say. He wanted to give us a little info on how to pronounce the Burj Khalifa, the tallest tower that we mentioned in our space elevator podcast. Do you remember talking about that?

Robert Lamb: Yeah, this was the one on space elevators.

Allison Loudermilk: So he told us the correct pronunciation. And then he was talking about how the tower was named. And Burj means tower and Khalifa is the name of the current president. And it literally translates to Tower of Khalifa. So thanks Abdullah. Appreciate the info. We have a ton of emails from lefty wannabes. A lot of people wrote in to talk about this whole left-handed guitarist thing that we got, too, in our podcast.

Robert Lamb: But wait, lefty wannabes?

Allison Loudermilk: I think there are some lefty wannabes out there. I'm just going to put that out there.

Robert Lamb: That's - I don't know.

Allison Loudermilk: That's because you're a righty.

Robert Lamb: Yeah, but I don't want to be a lefty.

Allison Loudermilk: Well, you should because we're awesome. So after our podcast on lefties, a couple of guys wrote in to tell us that lefties are the only ones in their right minds. Yes, indeed we are. And to tell us your take on left-handed guitarists. So here's what listener Jake had so say. "Although right-handed, I do know that if you're a lefty guitarist you have to use your left hand to strum and right hand to hold down the chords. So lefties hold the guitar upside down." Jake also told us that Paul McCartney, the famous Beatle's start is a lefty and he had trouble learning guitar until he looked at another lefty guitarist and saw the strings strung upside down. That's pretty interesting.

So even more, this turned out to help Paul McCartney when he met John Lennon because it meant that they could sit across from each other and see a mirror image and learn songs that way.

Robert Lamb: Oh, wow.

Allison Loudermilk: Andrew wrote in something along the same lines. He also brought up Phil Collins. And he was saying that there are no other left-handed instruments that he could think of, other than southpaw guitars. I do think he might've just wanted to bring up Phil Collins.

Robert Lamb: Wait, I though Phil Collins played the drums.

Allison Loudermilk: He does, but he was saying that drummers set up their drum kit in a mirror image of the usual way - so a special lefty way, if you will.

Robert Lamb: Oh, cool.

Allison Loudermilk: William wrote in to tell us that, aside from left-handed guitars, firearms are something that are left-handed designed. And this is pretty critical, because when you consider a firearm, if you have a lefty using a firearm designed for a righty, then you can wind up with shells being ejected.

Robert Lamb: Oh, yeah. I never thought of that. You don't want to have shells ejecting into your face every time you fire the gun. That's a design flaw.

Allison Loudermilk: Yeah. William tells us you definitely don't want this in a firefight. So I totally trust William on that. An Garret is now frightened of his left-handed girlfriend should she ever decide to fight him.

Robert Lamb: He should be. She's got the advantage.

Allison Loudermilk: And Jim from New Jersey's fledgling fencing career may have been cut short due to some tricky lefties in his college phys ed class.

Robert Lamb: Oh, man.

Allison Loudermilk: I took fencing in college, and I'm a lefty.

Robert Lamb: Were you any good?

Allison Loudermilk: I don't think I went up against Jim because I went to an all girls school. But I might've been okay. And Val, our friendly neighborhood maker of prosthetic devices, wrote in again to talk about her left-handedness. And she was mentioned the whole Kerr/Carr thing from Scottish history. Apparently, there's a clan called the Kerr Clan or Carr Clan that are known for being left-handed. So much so that the Kerr Castle built it's spiral staircases backwards so they could have that fighting advantage Robert and I were mentioning. And Val asked where some of my family was from, and we do have a little Scottish in there. So I don't know if it's Kerr/Carr, but -

Robert Lamb: So wow. Some of your ancestors might've built a crazy staircase designed to fight on.

Allison Loudermilk: Maybe that explains why my dad always wears a kilt.

Robert Lamb: Does he? Oh, yeah.

Allison Loudermilk: Sorry, dad. And on an unrelated note, Richard wrote in to tell us that he's fit, he's small, and the mosquitoes love him. He wasn't sure why. I think it may be because you're irresistible, Richard. So thanks for that.

Robert Lamb: At one point, we received a lot of comments about lefties and guitars, but nobody was able to answer how do lefties use guitar teaching as a seduction tool.

Allison Loudermilk: Yeah, we're going to leave that one outstanding for you guys. So send us the answer. We're looking for it - sciencestuff@howstuffworks.com. Or hook up with us on Facebook.

Robert Lamb: Yeah, on Facebook we're Stuff from the Science Lab. And on Twitter, we're @LabStuff. So check us out.

Allison Loudermilk: All right. That's all I got. Thanks for listening, guys.

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