0:00:06.196,0:00:09.496 >> So now what we understand is that[br]all bacteria can talk to each other. 0:00:09.836,0:00:14.556 They make chemical words, they recognize[br]those words, and they turn on group behaviors 0:00:14.556,0:00:18.916 that are only successful when all[br]of the cells participate in unison. 0:00:19.206,0:00:21.016 And so now we have a fancy name for this. 0:00:21.156,0:00:22.526 We call it "quorum sensing". 0:00:22.746,0:00:24.476 They vote with these chemical votes. 0:00:24.786,0:00:27.916 The vote gets counted, and then[br]everybody responds to the vote. 0:00:28.656,0:00:32.546 And what's important for today's talk is that[br]we know that there are hundreds of behaviors 0:00:32.546,0:00:35.376 that bacteria carry out in[br]these collective fashions, 0:00:35.426,0:00:38.706 but the one that's probably the[br]most important to you is virulence. 0:00:39.116,0:00:43.106 So it's not like a couple bacteria get in you,[br]and then they start secreting some toxins. 0:00:43.106,0:00:44.046 You're enormous. 0:00:44.236,0:00:45.896 That would have no effect on you. 0:00:45.896,0:00:46.796 You're huge. 0:00:46.796,0:00:51.006 But what they do, we now understand,[br]is they get in you; they wait. 0:00:51.216,0:00:52.196 They start growing. 0:00:52.196,0:00:55.156 They count themselves with these[br]little molecules, and they recognize, 0:00:55.206,0:00:56.556 when they have the right cell number, 0:00:56.786,0:01:00.226 that if all of the bacteria launch[br]their virulence attack together, 0:01:00.446,0:01:03.786 they're going to be successful[br]at overcoming an enormous host. 0:01:06.516,0:01:09.756 [ Applause ] 0:01:10.256,0:01:13.186 >> Hi! I'm delighted to be back[br]to give you a little progress 0:01:13.186,0:01:15.486 about what we've been doing in quorum sensing. 0:01:15.816,0:01:19.886 And so today, I want to tell you one story[br]about how we're taking what we learned 0:01:19.886,0:01:24.606 about these bacteria talking together and[br]trying to interfere with that conversation, 0:01:24.836,0:01:27.616 to make a fundamentally new kind of antibiotic. 0:01:27.736,0:01:32.736 And so the story I'll tell you about concerns[br]this pathogen, Pseudomonas aeruginosa. 0:01:33.236,0:01:36.486 This is the bacterium that kills[br]people who have cystic fibrosis. 0:01:36.816,0:01:40.576 It kills immune-compromised[br]people, and it causes infections 0:01:40.576,0:01:43.686 when you get a catheter, a[br]stent or a breathing tube. 0:01:43.946,0:01:47.496 And the reason Pseudomonas is so virulent is 0:01:47.496,0:01:50.646 because of this chemical[br]communication, this quorum sensing. 0:01:51.026,0:01:56.176 What Pseudomonas does is that as it grows,[br]it makes and releases small molecules, 0:01:56.176,0:01:58.266 which are the red triangles on this slide. 0:01:58.636,0:02:01.686 And so as the cells grow, these[br]molecules that are outside 0:02:01.686,0:02:04.516 of the cells increase in[br]proportion to cell number. 0:02:04.816,0:02:09.106 And as you heard on the clip, when the[br]bacteria detect that those molecules are there, 0:02:09.396,0:02:12.386 they interpret that that means[br]there's other cells around. 0:02:12.686,0:02:16.936 And then, as a collective, all of[br]the bacteria together make a biofilm, 0:02:16.936,0:02:19.976 which is how they sit on[br]surfaces and cure to tissue. 0:02:20.286,0:02:24.756 And then the group together secretes the[br]poisons, the toxins that make us sick. 0:02:25.126,0:02:26.436 So that's quorum sensing. 0:02:27.346,0:02:30.146 And so we want to be able to[br]interfere with that conversation. 0:02:30.836,0:02:34.076 And so we know what the molecule[br]is that Pseudomonas talks with. 0:02:34.256,0:02:36.796 It's the one that's on the[br]left side of this slide. 0:02:37.236,0:02:41.516 And so what we did, using chemistry, is[br]we changed the structure of that molecule 0:02:41.666,0:02:43.026 to make the one that's on the right. 0:02:43.616,0:02:47.256 And so what that chemistry did was[br]it changed the signal molecule, 0:02:47.426,0:02:49.286 the word, into an inhibitor. 0:02:49.596,0:02:52.466 So we changed the molecule[br]that turns on quorum sensing 0:02:52.656,0:02:55.236 into a molecule that shuts down quorum sensing. 0:02:55.626,0:02:57.936 So what happens if you have such a molecule? 0:02:58.326,0:03:00.186 So first, I'll talk about biofilms. 0:03:00.446,0:03:04.386 So in this petri plate, what we've done[br]is we've put Pseudomonas in the middle 0:03:04.386,0:03:06.576 of the petri plate, and what[br]I hope you can see is 0:03:06.576,0:03:09.136 that the bacteria have spread out to the edges. 0:03:09.446,0:03:11.066 That's this biofilm formation. 0:03:11.326,0:03:15.656 As a group, they move out over the plate,[br]and that could be like your tissues. 0:03:16.456,0:03:18.116 But we have this inhibitor. 0:03:18.326,0:03:21.556 So now if we do the experiment, and[br]we put the Pseudomonas in the plate, 0:03:21.716,0:03:25.956 and we add the inhibitor, what you can[br]see is that the Pseudomonas can't move. 0:03:26.116,0:03:26.746 So that's good. 0:03:26.746,0:03:28.176 That's step one in the infection. 0:03:28.176,0:03:31.696 It seems like our inhibitor can[br]shut down biofilm formation. 0:03:32.206,0:03:34.766 The next question for us is,[br]what about these poisons, 0:03:34.766,0:03:37.016 these toxins, that Pseudomonas secretes? 0:03:37.356,0:03:39.056 So now you're looking at an experiment, 0:03:39.056,0:03:42.646 and in the lefthand test tube,[br]that's wild-type Pseudomonas. 0:03:43.056,0:03:46.436 It's doing quorum sensing, and[br]it's secreted these toxins. 0:03:46.676,0:03:49.816 And when it secretes those[br]toxins, the bacteria turn green. 0:03:50.116,0:03:53.256 In the middle test tube, that's[br]a mutant that we've made, 0:03:53.256,0:03:55.676 where we've knocked out its[br]quorum-sensing system. 0:03:55.896,0:03:57.956 So that mutant has no communication. 0:03:58.216,0:04:00.496 And what you can see is that[br]the bacteria are colorless. 0:04:00.896,0:04:03.666 They can't secrete the toxin,[br]so they don't turn green. 0:04:04.376,0:04:09.456 The righthand test tube shows you wild-type[br]Pseudomonas that we've added our inhibitor. 0:04:09.646,0:04:14.026 And what I hope you can see is that the[br]inhibitor greatly decreases the ability 0:04:14.026,0:04:16.886 of Pseudomonas to secrete that green poison. 0:04:17.246,0:04:18.246 So now we're in business. 0:04:18.246,0:04:20.836 It looks like at least in the[br]lab, we can shut down biofilms, 0:04:20.836,0:04:23.016 and we can shut down toxin secretion. 0:04:23.286,0:04:24.796 So what about in an infection? 0:04:25.326,0:04:29.346 So in this experiment, you're looking[br]at an animal model system that we have 0:04:29.346,0:04:31.236 for Pseudomonas infection in the lab, 0:04:31.546,0:04:34.716 and all we do is measure whether[br]the animals are alive or dead. 0:04:35.166,0:04:37.376 And so on the line that you[br]looking at, obviously, 0:04:37.376,0:04:40.436 if we don't add pseudomonas,[br]the animals are perfectly fine. 0:04:41.096,0:04:45.976 If we give a Pseudomonas infection, now what[br]you can see is that all of the animals die 0:04:46.026,0:04:48.946 within the first day after the infection starts. 0:04:49.326,0:04:53.976 But if we do that, we give the Pseudomonas[br]infection, and we give that inhibitor molecule 0:04:53.976,0:04:56.556 that I showed you, what you[br]can see with the third line is 0:04:56.556,0:04:59.566 that we can greatly improve[br]the outcome for the animal. 0:04:59.896,0:05:04.326 So in fact, we think now that there must[br]be merit to this idea of interfering 0:05:04.326,0:05:08.416 with chemical communication, and that[br]maybe this could form the foundation 0:05:08.686,0:05:10.556 of a new type of therapeutic. 0:05:11.086,0:05:15.486 And so what we're doing in the lab, right now,[br]is we're taking the molecule that I showed you, 0:05:15.486,0:05:19.316 and we have to make it more[br]medicine-like we have to build in potency, 0:05:19.316,0:05:21.276 and we have to make that molecule safe. 0:05:21.926,0:05:25.986 The second thing is that we got inspired by[br]that biofilm experiment that I showed you, 0:05:25.986,0:05:27.926 and we're working with engineers now to try, 0:05:27.926,0:05:31.736 to try to embed those inhibitor[br]molecules into materials. 0:05:31.816,0:05:37.016 And the idea is that maybe we could[br]make infection-resistant catheters, 0:05:37.016,0:05:38.616 or stents or breathing tubes. 0:05:39.106,0:05:42.316 And then finally, I'm just telling you one[br]little vignette that's about Pseudomonas. 0:05:42.316,0:05:45.436 We work on lots of globally-important[br]pathogens in my lab, 0:05:45.706,0:05:50.306 and we're having similar success doing these[br]kinds of strategies in other bacteria as well. 0:05:50.516,0:05:54.966 And then to finish, I just want to show you the[br]two students who did the work, Colina Loflin 0:05:54.966,0:05:55.916 and [inaudible] Drescher [phonetic]. 0:05:55.946,0:05:58.946 They both work in the lab, and I'm lucky[br]to get to work with them every day. 0:05:59.256,0:05:59.946 Thanks for having me back. 0:06:00.186,0:06:02.186 [ Applause ] 0:06:02.356,0:06:02.716 >> So interesting.