WEBVTT - Symbioses 0:00:07.810 --> 0:00:12.450 Today we're talking about symbioses, which are when organisms coexist. Yeah, 0:00:12.510 --> 0:00:15.590 it's a broad term, and it does encompass parasitism, but 0:00:15.650 --> 0:00:17.489 today I'm going to do my best to keep the 0:00:17.530 --> 0:00:20.270 parasite examples to a minimum. We're going to be talking 0:00:20.290 --> 0:00:22.930 about the symbioses that made us who we are, the 0:00:22.950 --> 0:00:26.470 symbioses that turn rock into soil, and the symbioses that 0:00:26.510 --> 0:00:29.480 have a surprising number of layers. We're going to be 0:00:29.520 --> 0:00:33.680 talking about how symbioses aren't always what they seem, and 0:00:33.740 --> 0:00:38.540 sometimes good interactions can turn bad. Welcome to Daniel and 0:00:38.560 --> 0:00:40.320 Kelly's Symbiotic Universe. 0:00:40.340 --> 0:00:54.450 Hi, I'm Daniel. 0:00:54.470 --> 0:00:57.180 I'm a particle physicist who likes to think about aliens. 0:00:57.460 --> 0:01:00.460 And I have a proposed new alternative title for the podcast, 0:01:00.480 --> 0:01:03.450 which is It's Complicated with Daniel and Kelly. 0:01:03.750 --> 0:01:07.860 Hi, I'm Kelly Wienersmith. I study parasites and space. And 0:01:07.920 --> 0:01:10.000 that sounds, yeah, that's great. Let's go ahead and change 0:01:10.020 --> 0:01:14.619 it right now. I think either it's complicated or it depends. 0:01:14.640 --> 0:01:17.260 Or the gray areas are sometimes the most interesting, although 0:01:17.280 --> 0:01:21.630 that's a little wordy. Yeah, exactly. The acronym doesn't flow 0:01:21.770 --> 0:01:23.610 off the tongue quite as nicely, you know, as DKU. 0:01:23.650 --> 0:01:23.830 Yeah. 0:01:25.450 --> 0:01:29.929 So this episode was inspired by a question from Discord 0:01:30.050 --> 0:01:31.410 user Quantum Cat. 0:01:31.670 --> 0:01:32.970 Love Quantum Cat. Yep. 0:01:33.300 --> 0:01:33.640 Yep. Yep. 0:01:33.670 --> 0:01:36.240 And just like always, I forgot to ask their first 0:01:36.720 --> 0:01:42.140 IRL name before we started recording. But here is Quantum 0:01:42.160 --> 0:01:42.880 Cat's question. 0:01:43.380 --> 0:01:45.880 Hi, Daniel and Kelly. This is Brandon, also known as 0:01:46.000 --> 0:01:50.760 Quantum Cat. I have a question about nested symbionts. I 0:01:50.780 --> 0:01:55.660 was reading about mealybugs, which suck sap from plants. And 0:01:55.680 --> 0:01:58.720 I read that they contain a bacteria to help them 0:01:58.880 --> 0:02:02.320 digest the sap. But the unusual thing is that that 0:02:02.380 --> 0:02:06.680 bacteria is not enough. And that bacteria contains even smaller 0:02:06.740 --> 0:02:11.650 bacteria to help it digest the sap. So that's pretty unusual. 0:02:12.040 --> 0:02:14.489 Can you tell me more about the mealybug and its 0:02:15.010 --> 0:02:19.010 two bacterial helpers? Are there any other critters like that? 0:02:19.470 --> 0:02:19.790 Thank you. 0:02:20.320 --> 0:02:23.100 OK, so we are going to dig into the example 0:02:23.160 --> 0:02:26.280 that Quantum Cat refers to later in the show. Hang 0:02:26.400 --> 0:02:28.560 on for the second segment, but it's coming. 0:02:29.040 --> 0:02:32.850 So, Kelly, we all learned about symbiosis in elementary school. 0:02:32.990 --> 0:02:36.669 It's pretty straightforward. It's pretty simple. People helping each other, 0:02:36.910 --> 0:02:40.049 organisms helping each other out. Aren't you basically on a 0:02:40.090 --> 0:02:42.610 symbiosis on your farm with all your goats and sheeps 0:02:42.830 --> 0:02:44.250 or are they parasites on your time? 0:02:44.550 --> 0:02:46.150 Well, I was going to say that sometimes they feel 0:02:46.169 --> 0:02:49.790 like parasites. But but OK, so this is an interesting point. 0:02:49.950 --> 0:02:53.460 Let's jump right in here. What how would you define symbiosis? 0:02:54.570 --> 0:02:58.720 A relationship where organisms help each other. That's my Daniel 0:02:58.780 --> 0:03:01.000 fourth grade understanding of biology. 0:03:01.320 --> 0:03:03.240 Well, so I'm a little bit embarrassed to say that 0:03:03.280 --> 0:03:06.299 that was my grad school understanding when I went in. 0:03:06.760 --> 0:03:09.760 And so I was talking about a symbiosis as two 0:03:10.000 --> 0:03:13.380 organisms coexisting and interacting in a positive way. 0:03:13.400 --> 0:03:13.480 Yeah. 0:03:14.380 --> 0:03:15.340 And I was. 0:03:16.660 --> 0:03:17.220 Reschooled. 0:03:17.419 --> 0:03:20.800 I was schooled, man. I definitely got a bit of 0:03:20.820 --> 0:03:23.140 a look from the professor I was with, and they're like, 0:03:23.560 --> 0:03:28.220 symbiosis is a word that sort of covers a variety 0:03:28.240 --> 0:03:32.560 of interactions. It just means organisms coexisting and interacting together. 0:03:33.139 --> 0:03:37.080 And then you split it further into different interactions depending 0:03:37.120 --> 0:03:40.620 on whether or not those interactions are beneficial, negative, or 0:03:40.720 --> 0:03:43.440 not really doing anything. And so what you and I... 0:03:44.010 --> 0:03:47.730 thought was symbiosis is actually a mutualism. 0:03:48.270 --> 0:03:48.680 Oh, I see. 0:03:48.810 --> 0:03:53.010 And a mutualism is when both players benefit. And I 0:03:53.030 --> 0:03:54.750 don't know if you were just being nice and playing 0:03:54.790 --> 0:03:56.320 along with me to set me up there, but I 0:03:56.400 --> 0:04:00.660 really didn't in grad school. And this isn't entirely our 0:04:00.700 --> 0:04:04.320 fault because symbiosis has come to have a positive connotation. 0:04:04.400 --> 0:04:06.520 A lot of people think of it as a positive interaction, 0:04:06.540 --> 0:04:08.060 but it really encompasses a lot more. 0:04:08.340 --> 0:04:11.670 So you're telling me symbiosis is not just the positive 0:04:11.710 --> 0:04:14.400 version of It's the name of the whole category. And 0:04:14.420 --> 0:04:18.150 the positive version is called mutualism. Wow. I'm going to 0:04:18.250 --> 0:04:21.000 go look up my fourth grade teacher and let them know. 0:04:21.529 --> 0:04:23.650 Well, you know, I think it's possible that your fourth 0:04:23.670 --> 0:04:26.390 grade teacher got it right. And over time. 0:04:26.510 --> 0:04:27.469 Impossible. 0:04:27.610 --> 0:04:28.030 No. 0:04:28.750 --> 0:04:31.089 No, that hypothesis will be ruled out. Thank you very much. 0:04:31.170 --> 0:04:31.710 I was a. 0:04:31.670 --> 0:04:34.349 Very attentive fourth grade student. I'll have you know. 0:04:34.370 --> 0:04:36.870 I can imagine you sitting on the edge of your 0:04:36.950 --> 0:04:39.910 seat waiting for the information to come to you. But 0:04:39.930 --> 0:04:41.130 let's talk about mutualisms. 0:04:41.170 --> 0:04:42.050 Yeah. All right. 0:04:42.150 --> 0:04:43.969 Do you have an example of a mutualism in your 0:04:43.990 --> 0:04:46.550 head when you think about mutualisms? Because to me, there's 0:04:46.589 --> 0:04:48.530 a classic example, but I don't know if it's classic 0:04:48.550 --> 0:04:49.130 to everyone else. 0:04:49.370 --> 0:04:54.360 Example of a mutualism. What about like horses eat an 0:04:54.540 --> 0:04:58.610 apple and they get yummy apple and then they poo 0:04:58.690 --> 0:05:01.370 out the seeds in their poo, which is good for 0:05:01.410 --> 0:05:03.070 the seeds. So everybody benefits. 0:05:03.560 --> 0:05:07.760 Okay, yeah, so pollinators and seed dispersers, those are good mutualisms. 0:05:07.940 --> 0:05:08.440 Amazing. 0:05:08.740 --> 0:05:11.400 And you know what? That's definitely way more common than 0:05:11.760 --> 0:05:13.240 the mutualism that I'm thinking of. 0:05:13.380 --> 0:05:15.159 And it involves poo, so. 0:05:15.660 --> 0:05:16.360 Amazing, right? 0:05:16.420 --> 0:05:19.060 No, I'm totally on board right from the beginning. But 0:05:19.380 --> 0:05:21.610 the one that I think of as like the classic example, 0:05:21.650 --> 0:05:25.250 I guess I specifically like to think of animals interacting, 0:05:25.830 --> 0:05:28.490 is cleaner fish in the Great Barrier Reef. Have you 0:05:28.510 --> 0:05:29.110 heard of these? 0:05:29.130 --> 0:05:29.190 No. 0:05:29.550 --> 0:05:30.320 No, tell me. 0:05:30.430 --> 0:05:33.250 So these are fish where they will set up cleaning 0:05:33.330 --> 0:05:37.030 stations and bigger fish like sharks and groupers and stuff 0:05:37.050 --> 0:05:39.770 like that. They will come in. They'll open their mouth 0:05:39.870 --> 0:05:43.210 really big. And the cleaner fish will go inside and 0:05:43.250 --> 0:05:46.370 like pick out parasites and sort of clean their teeth. 0:05:46.450 --> 0:05:48.570 And then they'll like go along the exterior of the 0:05:48.670 --> 0:05:51.170 animal and like pick off all of the ectoparasites that 0:05:51.190 --> 0:05:54.589 are on there. And so they get a meal and 0:05:54.630 --> 0:05:58.730 whoever visited their cleaning station gets gets parasites removed and 0:05:58.770 --> 0:06:02.250 stuff like that. And so this is, in my world, 0:06:02.490 --> 0:06:04.510 one of the, like, classic examples of mutualisms. 0:06:04.910 --> 0:06:05.230 Wow. 0:06:05.430 --> 0:06:09.110 Yeah, well, very cool. Everybody definitely benefits. It's amazing, though, 0:06:09.150 --> 0:06:12.669 that fish basically set up, like, dental hygiene stations. That's cool. 0:06:12.950 --> 0:06:15.310 I mean, that's super cute, right? I think that's awesome. 0:06:15.330 --> 0:06:16.510 It's basically civilization. 0:06:16.810 --> 0:06:19.979 That's right. That's right. That's right. And, you know, I 0:06:20.010 --> 0:06:23.070 have seen people have some pretty negative interactions with their dentists. 0:06:23.450 --> 0:06:25.760 They might be more civilized than we are in the 0:06:25.800 --> 0:06:26.280 fish world. 0:06:26.940 --> 0:06:28.750 Well, I brought my son to one of those places 0:06:28.810 --> 0:06:31.370 where you dunk your feet in his vat and then 0:06:31.390 --> 0:06:32.710 the fish like nibble on it. 0:06:32.990 --> 0:06:33.310 No. 0:06:33.330 --> 0:06:37.050 I wasn't going to do it, but he thought, ooh, 0:06:37.070 --> 0:06:37.710 this is ticklish. 0:06:38.810 --> 0:06:41.810 Yeah, right. I have heard examples of people getting real 0:06:41.830 --> 0:06:45.620 bad infections from those fish tubs. And so I don't 0:06:45.660 --> 0:06:47.660 know that I would, I will not be recommending that 0:06:47.720 --> 0:06:50.400 on the show. But I can say that I used 0:06:50.420 --> 0:06:52.400 to work at this lake in Wisconsin, and when I 0:06:52.420 --> 0:06:55.060 would go in barefoot, the minnows would come by and 0:06:55.080 --> 0:06:56.790 pick the dead skin off my feet, which I'm sure 0:06:56.810 --> 0:06:58.230 is really going to gross a bunch of people out. 0:06:58.350 --> 0:07:00.310 But I remember feeling, oh! 0:07:00.350 --> 0:07:02.690 That's amazingly grosser than poo, yeah. 0:07:02.770 --> 0:07:03.250 Yeah, okay. 0:07:03.270 --> 0:07:06.349 Well, you know, we're always working on one-upping our prior accomplishments. 0:07:06.510 --> 0:07:07.880 So let's get into it. Let's make sure we have 0:07:07.890 --> 0:07:13.780 the definitions here. So symbiosis is two species coexisting. Mutualism 0:07:14.040 --> 0:07:17.830 is they both benefit. Is parasitism still when one of 0:07:17.870 --> 0:07:19.350 them is hurt and one of them is benefiting? 0:07:19.410 --> 0:07:19.850 That's right. 0:07:19.870 --> 0:07:21.150 Or is that more complicated? 0:07:21.550 --> 0:07:25.330 I mean, yeah. So there's lots of complicated examples. But yes, 0:07:25.410 --> 0:07:27.410 that is, you are correct. And so this is like 0:07:27.430 --> 0:07:30.350 tapeworms and trematodes and stuff like that. And so I 0:07:30.390 --> 0:07:32.270 won't go into too much detail because anyone who listens 0:07:32.290 --> 0:07:35.690 to DKEU is familiar with the idea of parasitism. And 0:07:35.710 --> 0:07:39.350 then there is commensalism, which is when one benefits and 0:07:39.390 --> 0:07:42.190 the other, it's just kind of like, meh, they're not helped. 0:07:42.230 --> 0:07:46.360 They're not harmed. And so examples here are cattle egrets. 0:07:46.940 --> 0:07:49.400 They will hang out in fields with cows. And as 0:07:49.460 --> 0:07:52.400 a cow walks through, it kicks a bunch of bugs 0:07:52.580 --> 0:07:54.680 up into the air that try to get away as 0:07:54.720 --> 0:07:56.380 the cow is moving through the grass. And then the 0:07:56.400 --> 0:07:59.460 cattle egrets pick those bugs out of the air and 0:07:59.540 --> 0:08:00.380 eat them for themselves. 0:08:00.620 --> 0:08:01.540 Wow, very cool. 0:08:01.760 --> 0:08:04.380 The cow doesn't care, but the cattle egret benefits. 0:08:05.080 --> 0:08:08.780 What about situations where one is hurt and the other 0:08:08.860 --> 0:08:10.280 one isn't helped or harmed? 0:08:11.240 --> 0:08:14.110 One is hurt... And the other isn't helped. 0:08:14.350 --> 0:08:15.050 Oh, spite. 0:08:15.070 --> 0:08:17.550 I think that's what you're talking about, right? 0:08:17.570 --> 0:08:19.630 Well, I was thinking about the cows and the bugs. 0:08:19.730 --> 0:08:22.450 The cows are kicking up the bugs. The egrets are benefiting. 0:08:22.990 --> 0:08:25.350 The cows don't care, but the bugs are definitely not 0:08:25.390 --> 0:08:27.989 happy about it. So what's the relationship between the cows 0:08:28.030 --> 0:08:31.710 and the bugs? The cows are casually destroying the lives 0:08:31.770 --> 0:08:33.750 of the bugs without caring about it at all. 0:08:34.170 --> 0:08:39.069 Interesting. Yeah, I mean, that's just an accident. I guess 0:08:39.090 --> 0:08:42.390 we could just call that a symbiosis. There's an interaction. Although, 0:08:42.450 --> 0:08:45.500 so that's more of a, like, short-term interaction. So the 0:08:45.620 --> 0:08:48.800 egrets and the cows are, like, coexisting together for a while. 0:08:48.860 --> 0:08:51.500 The egrets are, like, hanging out with the cows. Whereas 0:08:51.540 --> 0:08:53.780 the cow just has, like, a short-term interaction where it 0:08:53.920 --> 0:08:58.559 accidentally kicks off that bug. But I hadn't thought of that. 0:08:58.600 --> 0:09:00.900 I don't know. We've got to get you into ecology. 0:09:00.920 --> 0:09:04.360 There's a new category we're creating here. And the other 0:09:04.380 --> 0:09:07.240 question I have is like, how do we define these categories? Like, 0:09:07.320 --> 0:09:10.780 according to whom is this a benefit or a detriment? 0:09:11.000 --> 0:09:13.300 Is that fuzzy? Is that a judgment call? Or do 0:09:13.320 --> 0:09:16.300 we have like really crisp, clean definitions like we always 0:09:16.320 --> 0:09:17.860 do in biology? 0:09:17.940 --> 0:09:22.870 Yeah, we don't usually have crisp, clean definitions in biology, unfortunately. But, 0:09:22.920 --> 0:09:25.370 you know, you look at the two players in the 0:09:25.450 --> 0:09:30.430 symbiotic relationship and you do your best to calculate what's 0:09:30.470 --> 0:09:33.929 happening to them. So, you know, it's pretty intuitive that 0:09:34.010 --> 0:09:37.729 if you had a bunch of like blood sucking ectoparasites 0:09:38.230 --> 0:09:41.230 stuck to the outside of you and someone came along 0:09:41.410 --> 0:09:44.500 and picked those off, that's good for you. You've got, yeah, 0:09:44.860 --> 0:09:47.100 you've got fewer blood sucking ectoparasites. 0:09:47.140 --> 0:09:47.300 Right. 0:09:47.340 --> 0:09:50.020 And the cleaner fish ate them and that's their food. 0:09:50.080 --> 0:09:52.100 And so they got a meal. You brought the dinner 0:09:52.179 --> 0:09:55.240 to them. And so like, I feel like in that case, 0:09:55.500 --> 0:09:59.130 you can pretty clearly say, well, that probably benefits everybody, but... 0:09:59.630 --> 0:10:02.140 You know, this. is ecology, right? And so this stuff 0:10:02.179 --> 0:10:03.040 gets complicated. 0:10:03.380 --> 0:10:03.600 And. 0:10:03.620 --> 0:10:05.140 That's the name of the podcast. 0:10:05.559 --> 0:10:07.960 That's right. It's complicated with Daniel and Kelly. 0:10:08.400 --> 0:10:08.780 And so. 0:10:09.630 --> 0:10:13.780 These interactions can change either over time or depending on 0:10:13.820 --> 0:10:17.380 the environmental context or depending on the individual. So, for example, 0:10:17.440 --> 0:10:20.480 sometimes those cleaner fish, if they're hungry and there's not 0:10:20.500 --> 0:10:23.600 a lot of parasites on the fish they're cleaning, sometimes 0:10:23.660 --> 0:10:26.750 they'll grab a little bit of fin tissue or they'll 0:10:27.020 --> 0:10:29.349 grab a little bit of like the mucus that's a 0:10:29.390 --> 0:10:31.530 protective layer on the fish, but also could be a 0:10:31.570 --> 0:10:34.689 snack for the cleaner fish. And sometimes other cleaner fish 0:10:34.710 --> 0:10:37.850 will step in to punish the cleaner fish that's misbehaving. 0:10:38.460 --> 0:10:41.500 And I think sometimes also the fish that's visiting the 0:10:41.559 --> 0:10:44.440 dental station will punish a cleaner fish if they get 0:10:44.480 --> 0:10:46.730 out of line. But every once in a while, these 0:10:46.790 --> 0:10:48.990 relationships will turn negative and there needs to be like 0:10:49.050 --> 0:10:52.550 punishment to get everybody back in line because interests are 0:10:52.570 --> 0:10:53.450 not always aligned. 0:10:53.510 --> 0:10:55.170 Counselors. We call them counselors. 0:10:55.429 --> 0:10:57.819 Counselors. That's right. Fishy counselors. 0:10:58.179 --> 0:11:00.280 You guys need to go to therapy and figure this out. 0:11:00.610 --> 0:11:01.489 That's right. That's right. 0:11:01.610 --> 0:11:01.810 All right. 0:11:01.830 --> 0:11:05.459 So let's dig into an example of symbiosis and tell 0:11:05.480 --> 0:11:09.380 us about how it's more complicated than Daniel's fourth grade understanding. 0:11:09.720 --> 0:11:11.840 Well, I was thinking that today we could dig into 0:11:11.900 --> 0:11:15.320 some of the more epic symbiotic interactions. 0:11:15.420 --> 0:11:15.829 Cool. 0:11:16.090 --> 0:11:18.490 And one of the most epic. 0:11:18.770 --> 0:11:19.430 Most epic. 0:11:19.670 --> 0:11:23.069 Most epic. Like, you know, without this symbiotic interaction, we 0:11:23.130 --> 0:11:23.990 would not be here. 0:11:24.010 --> 0:11:24.750 Okay. 0:11:25.050 --> 0:11:27.130 Is the acquisition of mitochondria. 0:11:27.210 --> 0:11:28.010 So. Whoa. 0:11:28.390 --> 0:11:32.540 In the 1960s, Lynn Margulis pushed this idea of the 0:11:32.760 --> 0:11:36.090 endosymbiotic theory. Do you know of Lynn Margulis? 0:11:36.110 --> 0:11:38.570 Lynn Margulis, is she connected to Carl Sagan somehow? 0:11:38.890 --> 0:11:43.260 Yeah, and as a woman who's tired of having people say, oh, 0:11:43.300 --> 0:11:46.980 are you married to Zach Wienersmith? I hesitated, like, do 0:11:47.000 --> 0:11:49.420 we bring this up or not? But on the other hand, 0:11:49.480 --> 0:11:52.000 Carl Sagan is one of my favorite science communicators, and 0:11:52.020 --> 0:11:54.500 so I do bring it up. Yes, Lynn Margulis was, 0:11:54.520 --> 0:11:57.720 I think Sagan had two wives, and Lynn was the first. 0:11:58.760 --> 0:12:00.820 And she was, I think, Lynn Sagan at the time 0:12:00.860 --> 0:12:01.710 this idea came out. 0:12:01.920 --> 0:12:02.870 But did it end badly? 0:12:03.550 --> 0:12:07.709 It ended. You know, some endings are good. I don't 0:12:07.750 --> 0:12:08.630 know the details. 0:12:08.970 --> 0:12:11.030 Because I don't think anybody wants to be associated with, like, 0:12:11.290 --> 0:12:14.750 their ex that they're grumpy about. So context matters. 0:12:15.410 --> 0:12:20.080 Yeah, no, fair enough. So, Lynn Margulis' reputation is mixed, 0:12:20.300 --> 0:12:23.260 let's say. So, this idea that we're about to talk 0:12:23.300 --> 0:12:27.260 about is this amazing thing that she pushed forward. She 0:12:27.280 --> 0:12:29.120 got a bunch of people to accept that this might 0:12:29.160 --> 0:12:32.760 be what's really happening. But she also believes some conspiracy theories. Like, 0:12:32.800 --> 0:12:37.939 she was pushing the idea that HIV isn't what caused AIDS. So, 0:12:37.980 --> 0:12:39.420 she kind of ended up with a bit of a 0:12:39.580 --> 0:12:40.480 mixed reputation. 0:12:40.620 --> 0:12:40.820 But. 0:12:41.280 --> 0:12:42.780 All right, let's stick with the cool thing that she 0:12:42.830 --> 0:12:45.990 pushed forward. So Lynn Margulis was pushing this idea that 0:12:46.010 --> 0:12:49.489 the mitochondria that you find in eukaryotes and the chloroplasts 0:12:49.510 --> 0:12:53.099 that you find in things like plants... Were actually free 0:12:53.220 --> 0:12:57.360 living bacteria that were essentially co-opted. And now they live 0:12:57.400 --> 0:12:58.140 with us forever. 0:12:58.360 --> 0:13:00.120 I see. So they were out there in the wild 0:13:00.260 --> 0:13:02.600 and we basically made them tenants. 0:13:02.820 --> 0:13:03.080 Yes. 0:13:03.140 --> 0:13:03.920 Or like move in. 0:13:04.160 --> 0:13:04.319 Right. 0:13:04.340 --> 0:13:07.640 And so before this idea really got forwarded, people were 0:13:07.660 --> 0:13:10.439 thinking that like, oh, well, mitochondria and chloroplasts, they might 0:13:10.460 --> 0:13:13.219 just be like part of the cell membrane, sort of 0:13:13.260 --> 0:13:16.040 like invaginate. So it like kind of folds in and 0:13:16.080 --> 0:13:18.240 makes a little pocket and then it pinches off. And 0:13:18.280 --> 0:13:19.580 now you've got a mitochondria. 0:13:19.600 --> 0:13:19.680 Yeah. 0:13:20.210 --> 0:13:22.610 And so this idea had been, like, floated a couple 0:13:22.650 --> 0:13:25.270 times before, but Lynn Margulis really looked at the data, 0:13:25.450 --> 0:13:28.559 and she found... A couple of different observations that seemed 0:13:28.620 --> 0:13:32.380 to her to really say these mitochondria started as bacteria. 0:13:32.450 --> 0:13:33.590 And here are the observations. 0:13:33.730 --> 0:13:36.569 And let's remind everybody a mitochondria is the little piece 0:13:36.630 --> 0:13:39.450 of the cell that like produces energy. It's like the 0:13:39.490 --> 0:13:41.390 little factory or the oven or something. 0:13:41.670 --> 0:13:44.670 The powerhouse of the cell. I think that's what we. Yes, 0:13:44.730 --> 0:13:47.690 that's right. This helps produce ATP. These are the little 0:13:47.790 --> 0:13:52.730 energy sources for our bodies. And chloroplasts help plants convert 0:13:52.850 --> 0:13:54.130 sunlight into energy as well. 0:13:54.460 --> 0:13:54.940 Right. OK. 0:13:54.960 --> 0:13:57.870 Chloroplast for chlorophyll. All right. Got it. 0:13:57.920 --> 0:13:58.099 Yes. 0:13:58.400 --> 0:14:00.540 And so the idea is that we used to not 0:14:00.600 --> 0:14:02.970 be able to make ATP ourselves. We used to like 0:14:03.130 --> 0:14:05.510 work with an outside supplier and then we brought them 0:14:05.550 --> 0:14:06.589 in-house basically. 0:14:07.250 --> 0:14:10.589 So the idea is that four billion years ago, there 0:14:10.610 --> 0:14:15.260 were prokaryotes. And reminder, prokaryotes are cells that don't have 0:14:15.340 --> 0:14:19.080 any like nucleus and they don't have membrane bound organelles. 0:14:19.120 --> 0:14:19.960 These are like bacteria. 0:14:19.980 --> 0:14:20.180 Right. 0:14:20.980 --> 0:14:25.280 And then 2 billion years ago, an archaea, which they 0:14:25.320 --> 0:14:27.880 look a lot like bacteria, they differ in a couple ways. 0:14:27.920 --> 0:14:30.060 For example, I think they have a different sort of membrane. 0:14:30.710 --> 0:14:34.230 An archaea acquired a bacteria, and we don't know how 0:14:34.270 --> 0:14:38.410 it acquired that bacteria. When I was younger, the story 0:14:38.510 --> 0:14:41.080 I heard was that it was like an amoeba sort of. 0:14:42.350 --> 0:14:42.850 Yes, right. 0:14:42.950 --> 0:14:44.130 Speaking biologically. 0:14:45.050 --> 0:14:47.650 Exactly. Yes, right. And engulfing it as though it was 0:14:47.690 --> 0:14:50.730 going to take a meal. But then that bacteria just 0:14:50.790 --> 0:14:54.030 like survived and didn't die. But now we're not actually 0:14:54.100 --> 0:14:57.150 sure if it was parasitism or a predation. We don't 0:14:57.200 --> 0:15:00.160 actually know how it got there because amoeba are actually 0:15:00.220 --> 0:15:03.640 pretty advanced. And the kinds of organisms that we think 0:15:03.780 --> 0:15:07.780 acquired the bacteria, they don't do phagocytosis. They don't do 0:15:07.860 --> 0:15:09.960 this like thing that you were saying. 0:15:10.340 --> 0:15:13.380 That's the biological word for slurping. Phagocytosis. 0:15:13.420 --> 0:15:14.660 Phagocytosis, yes. 0:15:15.500 --> 0:15:15.700 I see. 0:15:16.280 --> 0:15:18.250 So anyway, we don't know how one got inside of 0:15:18.290 --> 0:15:21.670 the other, but about 2 billion years ago, that happened. 0:15:22.130 --> 0:15:25.650 So I guess I can get behind the idea that 0:15:25.970 --> 0:15:28.550 we used to collaborate with this thing, and then we 0:15:28.770 --> 0:15:30.860 shooped it up into the cell, and we can more 0:15:30.940 --> 0:15:34.380 closely collaborate with it. All cool. But then how do 0:15:34.400 --> 0:15:36.600 you get new cells to get one? Do they all 0:15:36.620 --> 0:15:37.920 have to find it themselves? 0:15:37.940 --> 0:15:38.010 Yes. 0:15:38.560 --> 0:15:40.880 Or do you now have the machinery inside you to 0:15:40.980 --> 0:15:43.840 make them? Or like when the cell divides, does this 0:15:43.900 --> 0:15:46.740 thing also divide? How does that get coordinated if it's 0:15:46.760 --> 0:15:48.920 like a foreign body? I'm used to the idea that 0:15:48.980 --> 0:15:51.540 there's like a single set of instructions in the nucleus 0:15:51.560 --> 0:15:53.830 for making the whole cell. But if you slip the 0:15:53.850 --> 0:15:56.380 thing from the outside, you don't have instructions for making it. 0:15:56.770 --> 0:15:57.750 So how do you pass it on? 0:15:58.230 --> 0:16:00.310 Yeah, great question. So first, I want to start with you. 0:16:00.350 --> 0:16:03.590 You said something about how the two organisms were like 0:16:03.650 --> 0:16:07.400 collaborating outside and then One, the other. 0:16:07.420 --> 0:16:09.400 You're going to correct Daniel's fourth grade knowledge again? 0:16:11.360 --> 0:16:12.680 Would you prefer if I didn't? 0:16:12.720 --> 0:16:14.490 Please do. That's what I'm here for. 0:16:14.820 --> 0:16:15.200 All right. 0:16:15.300 --> 0:16:18.440 Well, so we don't necessarily think that they were collaborating 0:16:19.160 --> 0:16:23.570 as outside partners initially. It could be that the bacteria 0:16:24.040 --> 0:16:28.670 was a pathogen and tried to invade the archaea and 0:16:28.710 --> 0:16:31.370 it just didn't take. And then over time, the nature 0:16:31.390 --> 0:16:32.550 of their relationship changed. 0:16:32.670 --> 0:16:35.030 Well, that's a much cooler story with a twist in it. 0:16:35.530 --> 0:16:38.470 Yeah, that's right. That's right. Sometimes your enemy becomes your friend. 0:16:38.510 --> 0:16:41.420 You should always have an open mind. But your question 0:16:41.580 --> 0:16:44.620 actually leads to part of how we figured out that 0:16:44.700 --> 0:16:47.820 this might have been a bacteria that was acquired because 0:16:48.400 --> 0:16:51.740 it was noted that mitochondria and chloroplasts divide in ways 0:16:51.780 --> 0:16:55.080 that look very similar to how bacteria divide. All right. 0:16:55.100 --> 0:16:58.729 So you've got host bacteria and it Sort of splits 0:16:58.790 --> 0:17:00.910 and divides. And if you want to get the little 0:17:01.010 --> 0:17:04.090 inside bacteria also, that thing also needs to have split 0:17:04.250 --> 0:17:06.950 and divide and then separated the right way so that 0:17:07.030 --> 0:17:10.100 both of the new cells also have the new symbiotic 0:17:10.240 --> 0:17:11.800 inside cell. Does that make sense? 0:17:11.820 --> 0:17:12.080 Yeah. 0:17:12.160 --> 0:17:13.400 How do you get that to coordinate? 0:17:13.680 --> 0:17:15.140 Well, that's a tough question. 0:17:15.240 --> 0:17:15.440 Yeah. 0:17:15.480 --> 0:17:16.940 I don't know how you get that to coordinate. I 0:17:16.960 --> 0:17:19.859 don't know how that worked over evolutionary time, but it 0:17:19.920 --> 0:17:22.540 was noted by like Lynn Margulis in her paper. She 0:17:22.580 --> 0:17:24.679 was like, look, these things are not being produced the 0:17:24.700 --> 0:17:26.400 way you would expect them to be produced if they 0:17:26.440 --> 0:17:29.940 were initially made by the organisms. The instructions are not 0:17:30.240 --> 0:17:34.070 in the DNA that's inside the nucleus. They seem to 0:17:34.109 --> 0:17:36.770 be doing their own replication. And like, I think in 0:17:36.850 --> 0:17:40.010 our liver cells, we have something like thousands of these mitochondria. 0:17:40.550 --> 0:17:42.950 in our cells, right? And so they're replicating all the time. 0:17:42.970 --> 0:17:46.190 They're doing their own thing. And it was noted that 0:17:46.330 --> 0:17:51.630 you inherit from your mom mitochondria sort of separate from 0:17:52.080 --> 0:17:55.520 the instructions that's in the nucleus. It's not like when 0:17:55.560 --> 0:17:58.359 you're born, the nucleus says, okay, start making mitochondria, and 0:17:58.380 --> 0:18:01.820 then they pop up. The mitochondria come along with everything else. 0:18:02.260 --> 0:18:04.379 I see. So this actually was a powerful piece of evidence. 0:18:04.859 --> 0:18:08.010 That they were once a separate organism because they're not 0:18:08.090 --> 0:18:10.510 included in the core DNA. They just sort of like 0:18:10.570 --> 0:18:13.409 replicate on their own. And we don't really understand that. 0:18:13.450 --> 0:18:15.209 But when the cell splits, you get some on one 0:18:15.250 --> 0:18:17.930 side and some on the other side and have their 0:18:18.090 --> 0:18:21.010 own DNA. I've heard of that mitochondrial DNA passed down 0:18:21.090 --> 0:18:21.770 through the mom. 0:18:22.050 --> 0:18:22.730 Right. Right. 0:18:22.990 --> 0:18:23.350 OK. 0:18:23.510 --> 0:18:23.650 Yes. 0:18:23.810 --> 0:18:26.859 And when you look at the sequences in mitochondria, you 0:18:26.880 --> 0:18:29.040 look at like the, you know, the genetic code inside 0:18:29.060 --> 0:18:32.260 of a mitochondria, that genetic code looks similar to genetic 0:18:32.320 --> 0:18:34.639 code that you find in bacteria. And it looks a 0:18:34.680 --> 0:18:38.620 lot more bacterial than it does like animal, for example. 0:18:38.640 --> 0:18:41.000 So that was more evidence that actually this used to 0:18:41.040 --> 0:18:42.520 be a bacteria. Does that make sense? 0:18:42.880 --> 0:18:45.080 That does. And it's fascinating because it tells me that 0:18:45.140 --> 0:18:49.490 like moms are more closely related genetically to their kids 0:18:49.510 --> 0:18:52.240 than than the dads are. It's not a 50-50 split 0:18:52.760 --> 0:18:57.050 because the mom passes along the mitochondria because she creates 0:18:57.109 --> 0:19:00.360 the actual baby and fills it with her own mitochondria. 0:19:00.400 --> 0:19:04.340 She's not taking the dude's mitochondria and mashing them together. 0:19:05.140 --> 0:19:08.679 You do always get mom's mitochondria. That's right. Yeah. Not dad's. 0:19:10.090 --> 0:19:12.439 Other pieces of information that Lynn Margulis used to make 0:19:12.460 --> 0:19:15.729 this argument is she noted that the membranes that surround 0:19:15.790 --> 0:19:18.889 things like mitochondria look kind of like the membranes you 0:19:18.950 --> 0:19:22.390 usually find in bacteria. So she really pushed this idea. 0:19:22.430 --> 0:19:25.190 She pushed it a little bit further. She kind of 0:19:25.369 --> 0:19:27.889 overdid it. She was arguing that like lots and lots 0:19:28.270 --> 0:19:32.149 of organelles are probably from bacteria that were acquired and 0:19:32.220 --> 0:19:36.720 she was seeing endosymbiosis everywhere. But we do have really 0:19:36.760 --> 0:19:40.280 good evidence that mitochondria, for example, and chloroplasts used to 0:19:40.300 --> 0:19:42.480 be bacteria that lived on their own and then they 0:19:42.530 --> 0:19:46.109 got absorbed by another organism and that opened up a 0:19:46.230 --> 0:19:48.669 bunch of pathways because now they had all this extra energy. 0:19:48.710 --> 0:19:52.619 They had these little dedicated energy sources and that appears 0:19:52.640 --> 0:19:54.859 to have opened up a lot of options for like 0:19:55.480 --> 0:19:58.850 diversity of size and function. And Nick Lane's book, The 0:19:58.869 --> 0:20:01.909 Vital Question, talks a lot about this. But yeah, we 0:20:01.930 --> 0:20:04.810 would not be here without this symbiotic relationship. 0:20:05.190 --> 0:20:08.200 Now, clearly we live in symbiosis with a lot of bacteria. 0:20:08.359 --> 0:20:11.060 They're all over our guts. Katrina told us about our microbiome. 0:20:11.080 --> 0:20:13.790 So there's lots of bacteria living in us, on us, 0:20:13.930 --> 0:20:17.020 that participate in our lives in crucial ways. And your 0:20:17.040 --> 0:20:18.940 description of them earlier made it sound like, well, these 0:20:18.980 --> 0:20:21.660 are just more bacteria that live in us, but inside 0:20:21.680 --> 0:20:24.850 the cell. And they participate in crucial cell activities. They 0:20:24.930 --> 0:20:27.230 replicate on their own. They do all this stuff and 0:20:27.250 --> 0:20:30.129 have their own DNA, which makes me wonder, like, are 0:20:30.150 --> 0:20:33.330 they actually part of the human body or are they 0:20:33.369 --> 0:20:35.750 part of the microbiome that's living in and on us? 0:20:36.350 --> 0:20:38.720 And I think you're saying that. They can't live on 0:20:38.740 --> 0:20:42.310 their own anymore. And they like become so specialized. They 0:20:42.330 --> 0:20:45.810 basically can only operate inside the human cell. 0:20:45.869 --> 0:20:46.090 Yes. 0:20:46.230 --> 0:20:46.750 Is that right? 0:20:47.050 --> 0:20:49.930 Absolutely. And let's take a break. And when we get back, 0:20:49.950 --> 0:20:52.570 we're going to talk about examples in nature that appear 0:20:52.650 --> 0:20:55.409 to be somewhere along that process. 0:21:15.550 --> 0:21:17.590 All right, we're back and we're talking about symbiosis. And 0:21:17.630 --> 0:21:20.110 I'm just now learning that there are bacteria living not 0:21:20.190 --> 0:21:25.109 only on me, but also inside me and inside my cells. 0:21:25.170 --> 0:21:27.150 But Kelly says they're kind of part of me now 0:21:27.380 --> 0:21:30.240 because they really, really made a home. But I feel 0:21:30.260 --> 0:21:32.540 like if they split on their own, they have their 0:21:32.760 --> 0:21:36.060 own mitochondria, and they're just passed down from the mom, 0:21:36.200 --> 0:21:38.340 I'm not sure they count as human bits. 0:21:38.920 --> 0:21:40.740 Okay, so I think that they do because they are 0:21:40.840 --> 0:21:41.879 clearly dependents. 0:21:42.390 --> 0:21:44.200 I don't think that's sufficient, though. Okay. 0:21:44.340 --> 0:21:46.200 What would you need to be sufficient? 0:21:48.000 --> 0:21:49.820 I don't know. I mean, there are definitely lots of 0:21:49.859 --> 0:21:53.160 organisms that need us to survive, but that doesn't mean 0:21:53.619 --> 0:21:57.500 that they're human, right? We're in symbiosis with them. For 0:21:57.540 --> 0:21:58.919 them to be part of us, I feel like they 0:21:58.940 --> 0:22:01.050 have to be part of the genetic code. Otherwise, who 0:22:01.130 --> 0:22:03.750 is it that's getting passed down, right? It's just part 0:22:03.770 --> 0:22:04.390 of the environment. 0:22:04.410 --> 0:22:04.830 All right. 0:22:04.869 --> 0:22:07.610 Well, so one, there is evidence that some of the 0:22:07.810 --> 0:22:10.990 genes that the bacteria used to have are now in us. 0:22:11.310 --> 0:22:12.950 So- Cool. 0:22:13.230 --> 0:22:13.350 Right. 0:22:13.369 --> 0:22:15.890 So the bacteria have been like in us getting like, 0:22:15.910 --> 0:22:17.430 I don't know, a free home and a free meal. 0:22:17.490 --> 0:22:20.120 But while they're inside of us, that means that they 0:22:20.170 --> 0:22:23.419 no longer have the opportunity to like meet and mingle 0:22:23.480 --> 0:22:27.560 with other bacteria. So so there's no longer, you know, 0:22:27.600 --> 0:22:30.960 the bacterial equivalent of sex. Yeah, there's no horizontal gene 0:22:30.980 --> 0:22:34.320 transfer or anything like that. And so over time, actually, 0:22:34.359 --> 0:22:37.520 their genomes tend to get smaller. smaller and smaller and 0:22:37.600 --> 0:22:40.159 some of their genes end up getting incorporated into the 0:22:40.200 --> 0:22:44.930 host genome until they're a pretty small subset of genes 0:22:44.970 --> 0:22:47.909 that do the specific things that we need mitochondria to 0:22:47.950 --> 0:22:50.810 do in our body. And so they've definitely come to 0:22:50.850 --> 0:22:55.410 depend on us. We absolutely could not survive without mitochondria. 0:22:55.490 --> 0:22:58.330 We would be goners without them. Whereas I think for 0:22:58.350 --> 0:23:01.550 the rest of your microbiome, like if you took antibiotics 0:23:01.570 --> 0:23:05.639 and you actually knocked out your microbiome, You'd be a mess. 0:23:06.500 --> 0:23:07.700 But like, I don't know. Do you think you could 0:23:07.720 --> 0:23:10.880 survive without most of the gut microbiome, for example? 0:23:11.320 --> 0:23:13.520 I don't think so. I think they're pretty essential. But 0:23:13.560 --> 0:23:17.260 give me the alternative story. Say this hadn't happened. Where 0:23:17.320 --> 0:23:19.050 would life be on Earth without this? 0:23:19.400 --> 0:23:21.730 I think that you could make the argument that we 0:23:21.750 --> 0:23:25.370 would still be at the prokaryotic stage of things like 0:23:25.410 --> 0:23:30.490 bacteria and archaea. It looks like. this extra energy that 0:23:30.510 --> 0:23:33.280 we were able to get by this symbiotic relationship sort 0:23:33.320 --> 0:23:35.700 of freed up a lot of the ability to, like, 0:23:35.880 --> 0:23:38.280 explore evolutionary space, as they would say. Like, we've got 0:23:38.300 --> 0:23:40.500 this energy to try new things. We can get bigger. 0:23:40.560 --> 0:23:40.960 We can. 0:23:41.200 --> 0:23:43.150 You don't think we would have figured it out ourselves? Like, 0:23:43.170 --> 0:23:46.770 we would have developed the same machinery? It's just biochemistry, right? 0:23:46.790 --> 0:23:47.389 It's not magic. 0:23:47.690 --> 0:23:49.879 Well, I mean, it looks like You know, four billion 0:23:49.900 --> 0:23:52.919 years ago, you start to get bacteria and archaea. And 0:23:52.960 --> 0:23:57.000 then two billion years after that, you get this endosymbiosis 0:23:57.040 --> 0:23:59.600 where one ends up inside of the other. And that's 0:23:59.680 --> 0:24:03.280 when eukaryotic organisms, so organisms with like a nucleus and 0:24:03.300 --> 0:24:06.350 membrane bound organelles, that's when we really started getting going. 0:24:06.830 --> 0:24:09.649 And so that does seem to be what kickstarted this 0:24:10.350 --> 0:24:13.149 like massive increase in diversity, but whether or not we 0:24:13.170 --> 0:24:14.410 could have figured out some other way. 0:24:14.330 --> 0:24:14.710 To do it. 0:24:15.130 --> 0:24:16.310 Impossible question, I know. 0:24:16.410 --> 0:24:20.020 Impossible question. Yeah, hard to say. But again, Nick Lane's book, 0:24:20.040 --> 0:24:22.320 The Vital Question, I think would argue that that was like, 0:24:22.540 --> 0:24:23.460 that is what you need. 0:24:23.780 --> 0:24:26.740 Fascinating. Well, I would love to see how this happened 0:24:26.820 --> 0:24:29.159 on alien planets so we could try to answer this question. 0:24:29.750 --> 0:24:32.990 Did something similar happen? Did they develop their own internal machinery? 0:24:33.109 --> 0:24:36.909 Is it just completely different biochemistry anyway? Can't wait to 0:24:36.950 --> 0:24:37.350 find out. 0:24:37.590 --> 0:24:39.570 Yeah, no, I would love to know that as well. 0:24:40.070 --> 0:24:43.350 But let's talk about sort of like an intermediate stage 0:24:43.450 --> 0:24:46.570 in this process. And so there have been examples where 0:24:46.650 --> 0:24:50.709 people have found like bacteria inside of bacteria and they 0:24:50.750 --> 0:24:53.210 seem to be helping each other out in some way 0:24:53.250 --> 0:24:56.350 and living together for like long periods of time. But 0:24:56.650 --> 0:25:00.370 because I like to add complication, there's An additional layer 0:25:00.410 --> 0:25:04.860 to this example. So Quantum Cat referred to a paper 0:25:05.160 --> 0:25:09.879 where scientists had studied a mealybug and the endosymbionts in 0:25:09.900 --> 0:25:14.180 the mealybug. So mealybugs are insects that have these like 0:25:14.240 --> 0:25:16.290 mouth parts that they can stick into plants and they 0:25:16.850 --> 0:25:19.550 suck out the sap. There's a lot of in this episode. 0:25:19.570 --> 0:25:20.530 Yeah. 0:25:21.480 --> 0:25:25.939 And they have bacteria that provide them with amino acids 0:25:26.060 --> 0:25:31.020 and some vitamins. And these bacteria are beneficial for the mealybugs. 0:25:31.119 --> 0:25:33.540 But you know how we were talking about how our 0:25:33.580 --> 0:25:38.050 mitochondria over time, they sort of degraded. They lost some 0:25:38.109 --> 0:25:40.070 genes that now are in our nucleus and they just 0:25:40.109 --> 0:25:43.290 became simpler sort of overall. One of the problems with 0:25:43.310 --> 0:25:45.550 these long term interactions where one is trapped in the 0:25:45.570 --> 0:25:47.600 body of another is that they do tend to sort 0:25:47.630 --> 0:25:50.560 of degrade over time because they don't have like sex 0:25:50.600 --> 0:25:54.520 and reproduction to sort of refresh their genetic information. So 0:25:54.560 --> 0:25:58.330 they noticed that the mealybugs, they have this amino acid 0:25:58.369 --> 0:26:02.520 providing bacteria. And if you look at different mealybug species, 0:26:02.880 --> 0:26:08.109 these different amino acid providing bacteria have different species of 0:26:08.290 --> 0:26:11.850 additional bacteria living inside of them. And so it looks 0:26:11.890 --> 0:26:15.310 like what's happening is that the main bacteria that was 0:26:15.350 --> 0:26:18.650 living inside the mealybug over time is sort of degrading 0:26:18.690 --> 0:26:21.790 and losing some of its awesome ability to provide amino 0:26:21.910 --> 0:26:24.149 acids and nutrients to the host. 0:26:24.390 --> 0:26:24.510 Hmm. 0:26:24.910 --> 0:26:27.650 And so it keeps picking up new bacteria that sort 0:26:27.690 --> 0:26:31.229 of replenish it and give it new abilities to be 0:26:31.300 --> 0:26:34.340 beneficial to the host. And so this is a symbiosis 0:26:34.400 --> 0:26:38.020 with three levels. It's a bug that has a bacteria 0:26:38.060 --> 0:26:41.420 that inside of it has a bacteria. And together, that 0:26:41.680 --> 0:26:45.420 unit helps the mealybug survive, which I thought was pretty awesome. 0:26:45.820 --> 0:26:48.420 And which part keeps picking up new partners? The bug 0:26:48.600 --> 0:26:49.879 inside the bug or the bug? 0:26:49.900 --> 0:26:50.620 Yeah. 0:26:51.869 --> 0:26:54.370 You can't call bacteria bugs in this example, Daniel. That's 0:26:54.390 --> 0:26:55.170 too confusing. 0:26:55.190 --> 0:26:58.070 All right. 0:26:58.090 --> 0:27:01.720 So there's, there's a bug with a bacteria and inside 0:27:01.760 --> 0:27:03.619 that bacteria is another bacteria. 0:27:04.100 --> 0:27:04.359 Right. 0:27:04.640 --> 0:27:09.000 And that bacteria inside the bacteria, the mini bacteria, the 0:27:09.060 --> 0:27:11.740 mini bacteria is the one that keeps getting replaced. 0:27:12.320 --> 0:27:12.700 Wow. 0:27:12.800 --> 0:27:16.750 So that's like the bacteria keeps using up his relationship 0:27:16.770 --> 0:27:18.830 and then finding like a second spouse and then a 0:27:18.890 --> 0:27:20.879 third spouse. And it's just like a, It's like a 0:27:20.940 --> 0:27:21.940 serial monogamist. 0:27:22.859 --> 0:27:27.320 Yeah, except that couple is living in service of some... 0:27:28.050 --> 0:27:30.400 I feel like this is kind of falling apart, but 0:27:30.920 --> 0:27:32.159 you need three players. 0:27:32.180 --> 0:27:33.330 It's a cult, basically, yeah. 0:27:33.510 --> 0:27:36.050 Well, there are relationships with more than two partners that 0:27:36.090 --> 0:27:39.609 aren't cults. We don't need to go too far down this. Anyway, 0:27:39.630 --> 0:27:42.230 I think the point is these three players together are 0:27:42.270 --> 0:27:43.609 needed to keep the bug going. 0:27:43.790 --> 0:27:43.990 Wow. 0:27:45.060 --> 0:27:47.919 And is that the only example of like these three 0:27:47.980 --> 0:27:50.080 level stories or is that a common thing to find 0:27:50.300 --> 0:27:50.900 in biology? 0:27:51.140 --> 0:27:51.500 Oh, man. 0:27:51.600 --> 0:27:54.340 OK, so this three level story, like I learned about 0:27:54.359 --> 0:27:56.720 when I was in grad school and it absolutely blew 0:27:56.760 --> 0:27:58.400 my mind when I learned about it. And I still 0:27:58.420 --> 0:27:59.900 think it's super cool today. So we're going to talk 0:27:59.920 --> 0:28:02.900 about it. OK, so tell me. P. aphids are these 0:28:03.200 --> 0:28:06.200 little bugs that like they eat plants. You often find 0:28:06.240 --> 0:28:09.180 them on like fava beans and stuff like that. And 0:28:09.560 --> 0:28:14.580 they can be infected by parasitoid wasps. This is not 0:28:14.740 --> 0:28:18.440 the symbiote. Well, this is a parasitic relationship we're talking 0:28:18.460 --> 0:28:19.639 about here. But in a second, we're going to be 0:28:19.660 --> 0:28:21.570 talking about bacteria living in the aphids. 0:28:21.700 --> 0:28:23.609 And are the aphids good or bad? I got to 0:28:23.630 --> 0:28:25.630 know who to root for here. Aphids are bad, right? 0:28:25.650 --> 0:28:28.609 Because they eat your crops. We like set ladybugs out 0:28:28.630 --> 0:28:30.210 in your backyard to eat the aphids, right? 0:28:30.369 --> 0:28:31.110 Exactly. Yeah. 0:28:31.150 --> 0:28:32.790 So we're anti-aphid. All right. 0:28:33.010 --> 0:28:36.340 Aphids are bad if you're a farmer. If you're an aphid, 0:28:37.660 --> 0:28:39.540 you probably think aphids aren't so bad. 0:28:39.560 --> 0:28:44.209 Are you being paid by Big Aphid, Kelly? 0:28:44.330 --> 0:28:44.710 Always. 0:28:44.750 --> 0:28:50.360 You're weirdly pro-aphid today. I'm anti-aphid, so go ahead. Now 0:28:50.380 --> 0:28:51.760 I'm on the side of these wasps. 0:28:52.110 --> 0:28:52.350 Okay. 0:28:52.590 --> 0:28:55.530 All right. I'm never opposed to someone being on the 0:28:55.570 --> 0:28:57.610 side of the wasps. So you're on the side of 0:28:57.630 --> 0:29:00.680 the wasps. These parasitoid wasps, they lay eggs inside of 0:29:00.700 --> 0:29:04.580 the aphid. Their babies hatch from these eggs. They burst 0:29:04.600 --> 0:29:05.860 out of the aphids and they kill them. 0:29:06.100 --> 0:29:06.420 Wow. 0:29:06.940 --> 0:29:10.350 Okay. So as you can imagine, that's very bad for 0:29:10.370 --> 0:29:10.830 the aphids. 0:29:11.250 --> 0:29:11.530 Yeah. 0:29:11.610 --> 0:29:13.310 I'm starting to feel bad for the aphids, actually. 0:29:13.600 --> 0:29:16.840 Oh, well, see, you know, nature is complicated. It's complicated 0:29:16.880 --> 0:29:23.940 with Daniel and Kelly. Okay, so P. aphids have a 0:29:24.040 --> 0:29:28.240 bacterial symbiont that defends them. And in fact, the name 0:29:28.290 --> 0:29:32.130 is called Hamatonella defensa. But I won't say it again. 0:29:32.150 --> 0:29:34.470 I use the scientific name just because defensa is in there. 0:29:34.510 --> 0:29:35.030 It's kind of cute. 0:29:35.210 --> 0:29:36.500 All right, I'll give it to you. 0:29:36.530 --> 0:29:39.930 All right, thank you. So it has this bacteria and cyanobacteria, 0:29:40.460 --> 0:29:47.300 noticed that when a parasitoid lays eggs in an aphid 0:29:47.360 --> 0:29:52.230 that has this bacteria, the egg laid by the parasitoid 0:29:52.250 --> 0:29:54.670 wasp was less likely to survive. And the aphid was 0:29:54.710 --> 0:29:56.270 more likely to be totally fine. 0:29:57.090 --> 0:29:59.410 So the wasp is attacking the aphid by sticking its 0:29:59.530 --> 0:30:03.720 eggs in there, but the aphid has little microbes inside 0:30:03.740 --> 0:30:05.420 of it which attack the egg somehow. 0:30:06.000 --> 0:30:08.120 Yes, which seem to be killing the egg in some way. 0:30:08.520 --> 0:30:09.420 Wow. Yeah. 0:30:09.580 --> 0:30:11.550 And so then they looked a little bit closer and 0:30:11.570 --> 0:30:16.060 they were like, hold on. It depends on the strain 0:30:16.080 --> 0:30:18.980 of the bacteria. So it's not like every aphid that 0:30:19.060 --> 0:30:23.510 has this bacteria in it is totally protected from parasitoid wasps. 0:30:23.890 --> 0:30:25.630 It looks like if you grow the bacteria in the 0:30:25.690 --> 0:30:27.310 lab for different amounts of time, you end up with 0:30:27.350 --> 0:30:30.080 these different strains. Some strains seem to do a better 0:30:30.120 --> 0:30:31.840 job of protecting than others. And they were like, well, 0:30:31.880 --> 0:30:37.320 what's different? And the thing that was different... was bacteriophages. 0:30:37.900 --> 0:30:41.100 So Katrina came on the show to talk about phages, 0:30:41.280 --> 0:30:47.260 bacteriophages being viruses that infect bacteria. So some bacteria were 0:30:47.300 --> 0:30:52.160 infected by a virus and this virus codes for toxins. 0:30:53.000 --> 0:30:56.440 And so the bacteria that have this virus in it 0:30:56.800 --> 0:30:59.760 are able to produce a toxin that appears to be 0:30:59.800 --> 0:31:02.480 the thing that is killing the parasitoid wasps. 0:31:02.970 --> 0:31:04.330 All right, hold on. I need a diagram. 0:31:04.410 --> 0:31:04.770 Okay. 0:31:04.790 --> 0:31:05.730 So we got a virus. 0:31:05.910 --> 0:31:06.090 Yep. 0:31:06.290 --> 0:31:07.350 Inside a bacteria. 0:31:07.370 --> 0:31:07.709 Uh-huh. 0:31:07.870 --> 0:31:08.970 Inside an aphid. 0:31:08.990 --> 0:31:09.450 That's right. 0:31:09.680 --> 0:31:13.340 That's producing a toxin that the aphid can use to 0:31:13.380 --> 0:31:17.160 attack the eggs that the wasp has also injected. inside 0:31:17.200 --> 0:31:20.340 this aphid. This aphid is a mess. Oh my gosh. 0:31:20.360 --> 0:31:20.660 I know. 0:31:20.720 --> 0:31:22.420 Well, I mean, you could think of it as a 0:31:22.460 --> 0:31:23.860 mess or you could think of it as having like 0:31:24.040 --> 0:31:27.380 an army on its side trying to help out, you know? 0:31:27.460 --> 0:31:29.780 No, it's a battlefield. Like the battle is going on 0:31:30.040 --> 0:31:31.140 inside the aphid. 0:31:31.340 --> 0:31:31.620 Yes. 0:31:31.880 --> 0:31:32.080 Yeah. 0:31:32.340 --> 0:31:32.860 It's amazing. 0:31:32.880 --> 0:31:33.180 Wow. 0:31:33.360 --> 0:31:37.540 But what's interesting is that these bacterial symbionts seem to 0:31:37.580 --> 0:31:40.880 get lost over time if there aren't parasitoid wasps around. 0:31:41.240 --> 0:31:43.290 So if you just grow aphids in a lab with 0:31:43.350 --> 0:31:48.060 no wasps around and Over time, you discover that fewer 0:31:48.100 --> 0:31:51.330 and fewer of the aphids still have this bacteria. But 0:31:51.370 --> 0:31:54.190 if you grow them in the lab with parasitoid wasps 0:31:54.230 --> 0:31:58.110 around and you watch them over many, many generations, more 0:31:58.150 --> 0:32:00.690 and more of them have this bacteria. And so that 0:32:00.730 --> 0:32:04.290 makes sense. The bacteria protects them from the parasitoid wasps. 0:32:04.710 --> 0:32:07.190 So you would expect the ones that have this bacteria 0:32:07.750 --> 0:32:10.580 to be more likely to survive and have babies. But 0:32:10.700 --> 0:32:13.420 why would you lose it when the wasps are not around? 0:32:13.460 --> 0:32:13.560 Right. 0:32:13.980 --> 0:32:16.300 Yeah, you need to maintain them somehow and they're expensive 0:32:16.340 --> 0:32:16.620 or what? 0:32:16.780 --> 0:32:19.900 Yeah, so they weren't able to figure out, like, what 0:32:20.000 --> 0:32:22.760 is the cost? But it does suggest that in environments 0:32:22.780 --> 0:32:26.000 where there aren't parasitoid wasps, there is some cost to 0:32:26.040 --> 0:32:30.020 this bacteria and the bacteriophage. And so that would suggest 0:32:30.060 --> 0:32:33.050 that in some environments, this is clearly a mutualism. This 0:32:33.110 --> 0:32:37.090 is clearly beneficial. But in other environments, you know, maybe 0:32:37.110 --> 0:32:38.910 the bacteria doesn't have a huge cost and it's a 0:32:38.930 --> 0:32:41.670 commensalism and it just gets lost through random processes. 0:32:41.690 --> 0:32:41.930 Right. 0:32:42.180 --> 0:32:44.880 Or maybe that bacteria actually does carry a cost and 0:32:44.940 --> 0:32:48.870 it's more like a parasite when there aren't parasitoid wasps around. 0:32:48.890 --> 0:32:49.530 Does that make sense? 0:32:49.650 --> 0:32:50.250 Interesting. 0:32:50.310 --> 0:32:50.610 Yeah. 0:32:50.670 --> 0:32:53.630 So it's worth paying the cost when you need it. 0:32:53.730 --> 0:32:56.390 But if you don't, then it's just a drag on 0:32:56.430 --> 0:32:57.430 your internal finances. 0:32:57.670 --> 0:33:00.430 Yes, exactly. And this is what I love about symbiotic 0:33:00.470 --> 0:33:04.630 relationships is that they are complicated. Complications in nature, I 0:33:04.850 --> 0:33:07.890 don't know, are interesting to me. But like which category 0:33:07.930 --> 0:33:09.930 you put this in, in terms of like what kind 0:33:09.950 --> 0:33:13.010 of symbiotic relationship is it? Depends a lot on what's 0:33:13.050 --> 0:33:16.290 in the environment, which I think is kind of fascinating. 0:33:16.830 --> 0:33:18.200 It seems like the right way to think about this 0:33:18.240 --> 0:33:21.560 is from a sort of ecological perspective, like the whole 0:33:21.720 --> 0:33:24.620 network of critters working together and talking to each other 0:33:24.660 --> 0:33:27.680 and communicating. Katrina's always talking about how the right way 0:33:27.700 --> 0:33:31.350 to think about microbes is also ecological. That's sort of 0:33:31.770 --> 0:33:34.910 her big thing. Instead of thinking about individual pathogens or whatever, 0:33:34.970 --> 0:33:36.610 you've got to think about the whole system. 0:33:36.910 --> 0:33:37.890 Yep, absolutely. 0:33:37.950 --> 0:33:38.450 Which is interesting. 0:33:38.870 --> 0:33:39.930 Really hard to do. 0:33:40.270 --> 0:33:42.170 Yeah. It's complicated. 0:33:42.250 --> 0:33:45.650 It's complicated. And that's why it's so important to, you know, 0:33:45.750 --> 0:33:48.270 do experiments that sort of build in their complications so 0:33:48.310 --> 0:33:50.280 you can look at all these different levels and then 0:33:50.410 --> 0:33:52.180 one day scale up to out in the field to 0:33:52.220 --> 0:33:55.980 see if you really understand what's going on there. Well, 0:33:56.040 --> 0:33:58.520 if you've been liking this conversation, you're going to love 0:33:58.560 --> 0:34:21.009 what comes next. All right, and we're back, and the 0:34:21.070 --> 0:34:23.430 last symbiotic relationship we're going to be talking about today 0:34:23.450 --> 0:34:27.640 are lichens. Daniel, let's continue today's tradition of putting you 0:34:27.680 --> 0:34:30.940 in the hot seat. What do you remember about lichens from, 0:34:31.120 --> 0:34:31.980 I don't know, kindergarten? 0:34:32.200 --> 0:34:36.000 All right. Fourth grade Daniel understands that lichens are some 0:34:36.160 --> 0:34:41.610 weird combination. They're like a... Fungus or a moss plus 0:34:41.650 --> 0:34:45.770 an algae or something like that. And they're working together 0:34:46.030 --> 0:34:47.490 and they like break down rocks. 0:34:48.010 --> 0:34:49.160 Yeah. Yeah. 0:34:49.260 --> 0:34:50.440 That's done. 0:34:50.660 --> 0:34:51.259 No, that was good. 0:34:51.460 --> 0:34:51.870 That's it. 0:34:51.920 --> 0:34:52.100 Yeah. 0:34:52.140 --> 0:34:54.240 No, let's dig in a little more, but that's good. 0:34:54.280 --> 0:34:54.460 Yeah. 0:34:54.500 --> 0:34:58.340 So the fungus is usually the like bigger partner in 0:34:58.380 --> 0:35:01.630 this interaction and it provides like structure and protection and 0:35:02.060 --> 0:35:04.560 And inside of it, you usually have algae and the 0:35:04.719 --> 0:35:08.950 algae are photosynthesizing, they're providing energy. And these tend to 0:35:08.969 --> 0:35:12.830 be very slow growing organisms that can survive in super 0:35:12.870 --> 0:35:13.750 harsh environments. 0:35:14.030 --> 0:35:14.260 All right. 0:35:14.280 --> 0:35:15.580 So fungus is the major player. 0:35:15.870 --> 0:35:18.589 Okay, yeah, fungus is the major player. And so, you know, 0:35:18.950 --> 0:35:22.470 as somebody who thinks about taxonomy pretty often, I know 0:35:22.750 --> 0:35:25.960 you're not a huge taxonomy fan, but what do you do? 0:35:26.020 --> 0:35:31.760 How do you characterize these organisms that like so clearly 0:35:31.820 --> 0:35:35.180 depend on one another, but like you've got two different players. 0:35:35.260 --> 0:35:38.550 Where does that fit in the tree of life? Very complicating. 0:35:38.910 --> 0:35:41.550 Maybe it doesn't make sense to draw arbitrary dotted lines 0:35:41.590 --> 0:35:42.130 around things. 0:35:42.570 --> 0:35:45.730 One of my favorite things in ecology and in evolution 0:35:45.790 --> 0:35:47.910 is when the tree of life has branches that sort 0:35:47.950 --> 0:35:50.320 of like come back together and touch each other or 0:35:50.360 --> 0:35:52.480 when it doesn't do what you would expect tree branches 0:35:52.540 --> 0:35:54.779 to do. That I always think is really fascinating. We 0:35:54.800 --> 0:35:57.580 have to think outside the box there. But so we 0:35:57.640 --> 0:36:01.270 tend to try to classify lichens based on the. big 0:36:01.510 --> 0:36:04.750 fungal partner that provides most of the structure. And I 0:36:04.910 --> 0:36:08.290 feel like this probably is because humans are very visual 0:36:08.450 --> 0:36:10.549 and probably initially it was just easier for us to 0:36:10.590 --> 0:36:12.990 be like, this is the part that I see. This 0:36:13.070 --> 0:36:15.400 one is green. This one is yellow. 0:36:15.420 --> 0:36:15.880 Right. 0:36:15.980 --> 0:36:18.980 But anyway, so we tend to classify based on what 0:36:19.020 --> 0:36:21.700 the fungal partner is doing. And there's something like 15 0:36:21.700 --> 0:36:25.259 to 20,000 species of lichens. And it looks like this 0:36:25.300 --> 0:36:28.130 symbiotic relationship is about 400 million years old. 0:36:28.150 --> 0:36:28.250 Wow. 0:36:30.170 --> 0:36:33.709 And this relationship popped up, we think, something like nine 0:36:33.750 --> 0:36:36.240 to 11 times. So it's not like once a fungus 0:36:36.280 --> 0:36:38.940 and an algal partner were like, let's work together. This 0:36:38.960 --> 0:36:42.359 has happened multiple times. There's some species that we think 0:36:42.580 --> 0:36:45.250 used to be in a lichen relationship and then they 0:36:45.270 --> 0:36:47.170 got a divorce and now they both live separately. 0:36:47.190 --> 0:36:49.330 You're saying they stopped liking each other? 0:36:49.350 --> 0:36:49.549 Yeah. 0:36:51.780 --> 0:36:55.700 Oh, why didn't I come up with that? Oh, my gosh. 0:36:55.760 --> 0:37:00.360 The hours that I spent researching this and I missed that. Anyway, 0:37:00.380 --> 0:37:03.960 I'm very disappointed. But what I'm excited about is, you know, 0:37:04.360 --> 0:37:05.239 it's complicated. 0:37:05.260 --> 0:37:05.330 Hmm. 0:37:05.820 --> 0:37:09.450 And it looks like the more people have spent time 0:37:09.550 --> 0:37:11.689 with lichens and the more we've been able to like, 0:37:12.010 --> 0:37:13.989 you know, this isn't very nice, but like grind up 0:37:14.050 --> 0:37:17.350 lichens and send them all through like genome sequencers to 0:37:17.370 --> 0:37:20.009 be like, okay, who is everybody that's in here? We've 0:37:20.070 --> 0:37:23.830 usually thought about lichens as fungus plus algae, but it 0:37:23.870 --> 0:37:28.490 turns out there's often like bacteria that are very consistent 0:37:28.590 --> 0:37:33.000 residents in lichens. And sometimes they do things like produce nitrogen, 0:37:33.040 --> 0:37:34.420 they're nitrogen fixing bacteria. 0:37:34.440 --> 0:37:34.680 Yeah. 0:37:34.880 --> 0:37:36.819 And so I think a lot of these lichens are 0:37:37.000 --> 0:37:39.040 not just two players. Like if you look at them 0:37:39.080 --> 0:37:43.840 more closely, there's probably bacteria or other kind, like multiple 0:37:43.880 --> 0:37:47.640 species of algae that are consistently showing up in the 0:37:47.680 --> 0:37:50.779 same species of lichen. And so lichen might actually be 0:37:50.840 --> 0:37:53.460 like not just two players, but some species might be 0:37:53.500 --> 0:37:57.299 like three players consistently found together or four players consistently 0:37:57.340 --> 0:38:00.910 found together so that they can provide everything that's needed 0:38:00.950 --> 0:38:02.010 for the lichen to persist. 0:38:03.770 --> 0:38:04.270 Interesting. 0:38:04.550 --> 0:38:09.090 What do you mean, interesting? That's fascinating, man. Imagine living 0:38:09.150 --> 0:38:11.950 in a triad where everybody had to play nice all 0:38:11.989 --> 0:38:15.010 the time. That's hard enough being in a dyad. 0:38:15.030 --> 0:38:18.910 I'm surprised it doesn't fall apart more often, yeah. 0:38:19.090 --> 0:38:21.410 Yeah, all right. Anyway, I think that's pretty cool. But 0:38:21.489 --> 0:38:24.220 one of my favorite things about lichens is that they 0:38:24.280 --> 0:38:29.000 help break rocks down into soil. And so they often 0:38:29.060 --> 0:38:31.620 stick to the side of things like rocks. And one 0:38:31.640 --> 0:38:34.870 of the things that they do is just very slowly 0:38:35.090 --> 0:38:38.240 grow into the like little nooks and crannies in the rock. 0:38:38.300 --> 0:38:41.200 And over time, they're able to just like create extra 0:38:41.239 --> 0:38:43.500 stress in the rock to start like cracking it and 0:38:43.540 --> 0:38:44.440 breaking it apart. 0:38:44.520 --> 0:38:45.080 Amazing. 0:38:45.239 --> 0:38:48.690 I know, right? When I watch tree roots that have 0:38:48.790 --> 0:38:52.690 lifted up sidewalks, for example, just like the fact that slow, 0:38:52.850 --> 0:38:55.529 persistent growth can do something like that, like that needs 0:38:55.550 --> 0:38:58.029 to be a bumper sticker. That's inspirational. 0:38:58.050 --> 0:38:58.140 Yeah. 0:38:58.440 --> 0:39:01.620 Well, it's one of those great insights into deep time, right? 0:39:02.080 --> 0:39:04.239 To show you the things that you thought were static 0:39:04.800 --> 0:39:09.350 or were uninfluential over time can change everything. It's really incredible. 0:39:09.650 --> 0:39:13.250 Yeah, it is totally inspirational. And additionally, some of these 0:39:13.310 --> 0:39:16.860 lichens are able to produce things like acids or other 0:39:16.880 --> 0:39:21.100 like mineral dissolving compounds that further break down through chemical means, 0:39:21.180 --> 0:39:24.540 not just like physical means. And that helps the lichen grow. 0:39:25.340 --> 0:39:27.300 And then one day the lichen will die and it 0:39:27.340 --> 0:39:29.710 will decay and become part of the soil. And through 0:39:29.730 --> 0:39:34.540 this process, you go from giant rocks to soil. And 0:39:34.760 --> 0:39:36.340 I just think that's absolutely amazing. 0:39:36.700 --> 0:39:39.379 And did we not have soil before lichen or was 0:39:39.440 --> 0:39:40.020 it just slower? 0:39:40.520 --> 0:39:43.380 There are multiple ways that you can get soil, and 0:39:43.400 --> 0:39:45.460 this is one of them. It's not like all of 0:39:45.520 --> 0:39:48.430 the soil on the planet we can tip our hats 0:39:48.469 --> 0:39:51.330 and say, thank you, lichen. But it's possible that there 0:39:51.370 --> 0:39:53.969 are some minerals in your body that were liberated from 0:39:54.070 --> 0:39:58.610 rocks by lichens. And I'd say probably even probable. And so, 0:39:58.710 --> 0:40:00.150 you know, thank you, lichens. 0:40:00.830 --> 0:40:02.250 We've all been soiled by lichens. 0:40:02.270 --> 0:40:05.210 Or spoiled. 0:40:05.550 --> 0:40:08.770 Spoiled, yeah. Man, you're on a roll today. I'm loving it, Daniel. 0:40:08.790 --> 0:40:09.509 I'm loving it. 0:40:09.960 --> 0:40:12.160 I'm just bringing my fourth grade sense of humor, you know, 0:40:12.180 --> 0:40:14.560 because I'm bringing my fourth grade level of expertise. 0:40:14.600 --> 0:40:18.879 Highly appropriate. Highly appropriate. And, you know, I may or 0:40:18.960 --> 0:40:22.739 may not have sat for a second and thought, do 0:40:22.840 --> 0:40:25.629 I know who the two partners are in a lichen? 0:40:25.650 --> 0:40:27.850 And I had to think about it for a second 0:40:27.870 --> 0:40:31.009 because I hadn't accessed that information for a while. And so, 0:40:31.030 --> 0:40:33.730 you know, did some deep reading before this. But one 0:40:33.750 --> 0:40:35.810 of the cool things about lichens is that when they 0:40:35.850 --> 0:40:40.710 are dried out and desiccated... It's really hard to kill them. 0:40:40.870 --> 0:40:43.509 Like when the fungus is all sort of like dried out, 0:40:43.550 --> 0:40:46.150 it does a really good job of protecting the algae inside. 0:40:46.230 --> 0:40:48.330 And so lichen have been like brought to space. And 0:40:48.350 --> 0:40:51.569 it turns out that they're super resistant to radiation when 0:40:51.610 --> 0:40:55.740 they're in this desiccated state. But when they are moist 0:40:55.800 --> 0:40:58.400 and active and like metabolically doing the stuff that they 0:40:58.440 --> 0:41:01.739 usually do, they're actually pretty darn sensitive to things like 0:41:01.840 --> 0:41:05.160 air pollution. And so they can be used as bioindicators. 0:41:05.200 --> 0:41:07.200 Like if you go to an area and there's like 0:41:07.239 --> 0:41:08.819 a lot of diverse lichen, you can be like, oh, 0:41:08.840 --> 0:41:11.180 the air quality here is probably pretty good. But if 0:41:11.219 --> 0:41:13.540 you notice that you're losing lichen in an area, that 0:41:13.580 --> 0:41:15.610 could be an indicator that the air quality in your 0:41:15.680 --> 0:41:18.190 area is going down. And so some ecologists are pushing 0:41:18.390 --> 0:41:21.750 lichen as a way of like monitoring how good the 0:41:21.810 --> 0:41:23.170 air quality is in an area. 0:41:23.650 --> 0:41:24.030 Whoa. 0:41:24.690 --> 0:41:24.850 Yeah. 0:41:24.950 --> 0:41:26.129 Are you liking the air or not? 0:41:26.950 --> 0:41:29.089 I'm not sure I'd be liking living in Beijing, but 0:41:29.150 --> 0:41:32.219 I hear that it's getting better there. And I like 0:41:32.239 --> 0:41:34.319 caribou and lichen tend to be a major food source 0:41:34.340 --> 0:41:36.920 for caribou. So what's not to like? N. 0:41:40.460 --> 0:41:40.640 All right. 0:41:40.660 --> 0:41:45.360 So Kelly, tell us, is symbiosis underappreciated in the general 0:41:45.400 --> 0:41:48.600 community out there? Do people not realize the power and 0:41:48.640 --> 0:41:51.060 the awesome impact of symbiosis in general? 0:41:51.530 --> 0:41:52.840 Gosh, I mean, I don't know. I think most of 0:41:52.910 --> 0:41:56.560 us appreciate symbioses, but we like appreciate them in a 0:41:56.600 --> 0:41:59.219 more fine grained way. Like, you know, I have dedicated 0:41:59.260 --> 0:42:04.989 my life to appreciating the category of symbioses, which is parasitism. 0:42:05.760 --> 0:42:06.859 You know, and so I think a lot of people 0:42:06.880 --> 0:42:09.600 are like, oh, I study mutualism. I study parasitism. I 0:42:09.640 --> 0:42:13.219 study commensalism or something. But like symbiosis is just such 0:42:13.239 --> 0:42:15.339 a broad term. But to be honest, I was kind 0:42:15.360 --> 0:42:17.340 of like, what am I going to do with this episode? 0:42:17.360 --> 0:42:19.860 This could be like, you could pick any species and 0:42:19.880 --> 0:42:23.410 there's like thousands of symbiotic interactions you could talk about. 0:42:23.719 --> 0:42:26.750 Because nobody lives in isolation, which means that everybody's in 0:42:26.790 --> 0:42:27.950 symbiosis all the time. 0:42:28.360 --> 0:42:31.670 Yeah, except symbiosis is meant to focus a little bit 0:42:31.710 --> 0:42:35.190 more in on like long-term interactions. And so like if 0:42:35.230 --> 0:42:37.549 you pass a stranger on the street, you wouldn't say 0:42:37.570 --> 0:42:40.090 you had a symbiotic relationship with them. But you do 0:42:40.110 --> 0:42:42.879 have a symbiotic relationship with your wife, for example. 0:42:44.360 --> 0:42:44.620 Yes. 0:42:45.460 --> 0:42:46.759 Definitely not parasitic. 0:42:46.880 --> 0:42:50.700 That's right. That's right. Here's hoping. And so anyway, none 0:42:50.719 --> 0:42:52.460 of us would be here if it wasn't for a 0:42:52.520 --> 0:42:55.859 symbiotic interaction that happened something like two billion years ago. 0:42:56.460 --> 0:42:59.360 Thank you, symbioses, for making us what we are. 0:42:59.380 --> 0:43:02.760 Hi, Daniel and Kelly. 0:43:02.900 --> 0:43:06.069 This is Brandon, otherwise known as Quantum Cat. That was 0:43:06.110 --> 0:43:10.710 another excellent episode. I found two things especially interesting. 0:43:11.090 --> 0:43:14.930 One is that for the mealybugs, the bacteria that it 0:43:14.989 --> 0:43:18.790 contains that have a bacteria inside of it, that bacteria 0:43:18.810 --> 0:43:21.370 inside of it can vary over time, and it's not 0:43:21.390 --> 0:43:22.529 just one species. 0:43:23.160 --> 0:43:26.680 And the other thing I thought was fascinating was the, um, aphid, 0:43:27.180 --> 0:43:30.380 that for defense against the wasp that predates upon it, 0:43:30.950 --> 0:43:34.129 it contains a bacteria that makes a toxin that goes 0:43:34.190 --> 0:43:37.450 after the wasp's eggs. And that if it's not predated 0:43:37.489 --> 0:43:37.890 by that. 0:43:37.830 --> 0:43:40.770 Wasp, the level of bacteria drops. 0:43:41.410 --> 0:43:45.060 That just is fascinating how nature works that way. So 0:43:45.120 --> 0:43:47.340 thank you again for an excellent episode. 0:43:54.170 --> 0:43:56.509 Thanks, everybody, for listening. 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