Hey guys,
First Chinese New Year after the afec! It has been a while since afec ended, but it still seems like yesterday to me. Sometimes I’ll get up and think that Peter is sleeping on the bed next to me. Still missing a lot of delicious food and tasty snacks in XTBG. Wish you guys a wonderful New Year! Gong Xi Fa Cai!
jer pin
Hey guys, how’s life so far? After I came back to Utah, things have been slowing down a lot and not as intense as when I were in China. Probably because when we get back to a familiar place, we tend to slack a bit, haha. But the afec course helped me to realize a lot of things, and basically motivated me to do things that I’ve always wanted to do. So I am really grateful that I had the chance to be at the XTBG conference. We have the first snow storm today. More to come, and the temperature will keep dropping until it reaches a negative value. Yeah, it doesn’t sound fun. But we have to deal with it. Hope all is well for you.
Hey guys,
I guess most of us should be arriving home by this time (except Bhakta, he said he would go back to Nepal by bicycle).
After a long journey, i finally arrived home in the States. Currently suffering a serious jet lag (time here is 14 hours behind BeiJing). Sleeping at 4am and getting up at 4pm is BAD for an employee! Will start working tomorrow, so I have to force myself to get back to life here as soon as I can.
I hope none of you have problem getting back to normal rhythm. Thanks for the wonderful time we’ve spent together in the past 4 weeks. It will stay in my memory for a long long time. Wish you all be successful in your study and career, and of course, stay healthy! Keep in touch yea!
On July 10, Dr. Douglas Yu gave an excellent lecture on ‘Mutualism’. PowerPoint of that presentation can be found in Afec-X website under the ‘Lecture’ section. Dr. Yu’s lecture can be divided into three components: Mutualism, Partner Choice, and using economic theory to explain mutualism. I found the lecture very interesting, especially that some of the ideas are very innovative and inspiring. I would discuss the concepts of that lecture in more details, with the focus on the mutualism between the shallow-water benthic squids (Family Sepiolidae) and light-emitting bacteria (Genus Vibrio).
Mutualism is an interaction between two organisms that increases fitness of one another, either through trading resources or increase survival rate from predator. Throughout the Afec-X course we’ve learned several classical examples of mutualism, for example fig and fig wasp, ant-plant interaction, etc. In the case of Sepiolid squid and Vibrio bacteria, symbiotic relationship not only increases the fitness of both organisms, it also allows them to occupy new habitat niches (Nishiguchi 2004). Symbiosis and mutualism are not supposed to be used as synonymous because symbiosis is a larger category and mutualistic is just one of the categories. But the interaction between Sepiolid squid and Vibrio bacteria is both symbiotic and mutualistic. The Vibro bacteria live inside the squid and produce light to help the host hunting its prey. The squid, in return, provides food for the bacteria. Thus, perhaps it is O.K. to use the term ‘symbiotic’ to interpret mutualism in the rest of the paper.
Sepiolidae-Vibro symbiosis has been intensively studied for decades, and most of the hypotheses have probably been tested and examined. One of the first things we would like to know was that how did squid and bacteria form a species-specific relationship? Several common hypotheses have been proposed to explain how natural selection worked in this symbiosis relationship (Nishiguchi 2004): i)Multiple bacteria species could infest Sepiolid squid, but Vibrio bacteria gave highest fitness to the host. So evolution has selected Sepiolid squid with Vibrio bacteria. Both organisms have co-evolved and eventually became a species-specific relationship. ii) Evolution of symbiotic bacteria was due to similar environmental factors with the host, and not due to specific host. If that was the case, the bacteria from the same habitat should be closely related and could infest multiple host species. As what stated in Nishiguchi (2004), many studies have shown that same Vibrio species that infest Sepiolid squid and monocentrid fish are genetically distinct, and they cannot infest different host family. So the idea of the cospeciation of Sepiolid squid and Vibrio bacteria has been supported, in general.
Then, how do the species stabilize the mutualistic interaction? That leads to the second part of Dr. Yu’s talk, Partner Choice. Partner Choice is a concept where the host can increase the rewards for cooperative partner and reduce the reward for non-cooperative partner (Sachs et al. 2004). The concept of Partner Choice has been strongly supported by the ant-plant mutualism in Edwards et al. (2006). However, the testing of Partner Choice hypothesis in squid-bacteria relationship is extremely difficult because there is no way we can examine the changes in host’s reward for the symbiotic bacteria.
In the last part of Dr. Yu’s lecture, he used economic theory of information to explain the Sepiolidae-Vibro symbiosis. I was really hoping to read the paper that Dr. Yu cited in the PowerPoint to better understand the economic theory. Unfortunately, I failed to locate the paper from the Web of Science. So the only thing I could do is write down my own understanding of that part of the lecture, and hopefully I won’t misinterpret the brilliant idea of Dr Yu and his colleagues.
The economic theory that Dr. Yu presented involves three parts: adverse selection, signaling and moral hazard. Adverse selection occurs when buyers and sellers have asymmetry information. For example, insurance companies tend to adversely or negatively select individuals with higher risk. So, the companies increase the insurance fee. The consequence of that is that individuals with lower risk become less likely to buy insurance. This will eventually end up with the collapse of the insurance industry. To avoid that, buyers and sellers need a signaling progress to be on the same page. Buyers provide the insurance company with some basic information of their heath, and insurance company will offer plans with different prices for different individuals based on their risks. Lastly, the moral hazard concept suggests that individuals who provide incorrect information (in other word less cooperative) will be punished and their services will be discontinued.
To apply the economic theory to biology, here is a direct quote from Nishiguchi (2004), ‘These types of functional interactions between host and symbiont can only be established when an avenue for the exchange of information has evolved specifically within the symbiosis.’ As indicated, signaling is an important procedure for the host and symbiont to establish and stabilize the mutualistic relationship. However, the study of signaling procedure in the Sepiolidae-Vibrio symbiosis was very challenging, for it was unclear what signals and how the host passed on to the symbionts, or vice versa. In 1999, Edward and Margaret discovered that light organ in the Sepiolid squid has enzymes that can transform oxygen into toxic component. Light-emitting bacteria can use up all the oxygen in the light organ to produce light, thus allowing them to live symbiotically with the Sepiolid squid. Edward’s finding presented a possibility that the Sepiolid squid selectively ‘chooses’ the light-emitting bacteria (and not other types of bacteria) to increase their fitness, which perhaps can be considered as a signaling procedure. Similar to partner choice study, moral hazard concept is very difficult to examine in an empirical research. If partner choice or moral hazard did happen in the squid-bacteria relationship, we would expect to see variation in Vibro bacteria concentration in squids that live in high resource habitat and low resource habitat. Perhaps in later future when molecular data can be used to quantify the amount of Vibrio bacteria in Sepiolid squid (maybe higher amplification means more bacteria?), the partner choice or moral hazard concepts can then be examined.
To summarize my understanding on the Sepiolidae-Vibrio symbiosis, the Sepiolid squid and Vibrio has been co-evolving to form a species-specific symbiotic relationship. During the cospeciation, Sepiolid squid has evolved a mechanism to stabilize the symbiotic relationship. Economic theory can be used to understand the interaction between organisms. However, limited research may be available to support the economic theory.
References
DouglasYu’s Lecture on ‘Mutualism’. PowerPoint slides available at
http://afec-x.ecologicalevolution.org/files/ppt/Douglas_Yu-Mutualisms_talk_AFEC-X.pdf
Edwards, D. P., M. Hassall, W. J. Sutherland, and D. W. Yu. 2006. Selection for protection in ant-plant mutualism: host sanctions, host modularity, and the principal-agent game. Proceedings of the Royal Society B 273:595-602.
Edward G. R. and J.M. Margaret. 1999. Oxygen-utilizing reactions and symbiotic colonization of the squid light organ by Vibro fischeri. Trends in Microbiology 7(10): 414-420.
Nishiguchi, M.K. 2004. Cospeciation between hosts and symbionts: The Sepiolid squid-Vibrio Mutualism. Cellular Origin, Life in Extreme Habitats and Astrobiology 4: 757-774.
Wollenberg, M.S. and Ruby, E.G. 2009. Population structure of Vibrio fischeri within the light organs of Euprymna scolopes squid from two Oahu (Hawaii) populations. Applied and Environmental Microbiology 75(1): 193-202.
I am not a blogger. I feel like writing a blog is no difference than writing a diary, in which everyday you have to THINK of something to write, different ways to write. For a lazy person like me, my diary was almost the same day after day, and eventually ended up copy-and-paste to reduce my workload. That diary habit didn’t last long of course. That’s just me.
There were several times I found myself in a very funny position. I received my master degree in Wildlife Biology from Utah State University under the department of Wildland Resources. Our department is mainly focusing on researching plants and terrestrial animals. However, my research was studying the phylogenetics (which should be in Biology Department) of freshwater mussel (should be in the department of Watershed Sciences). Sitting among a group of terrestrial animal/plant students and asking questions about aquatic organisms and genetic has always been awkward, but I’ve got to get used to it.
After receiving my master degree, my professor and I both think that writing is one of my major drawbacks. So I’d registered an English writing class that was designed for undergraduate students. Again, I was in an interesting position because that was the second time I took the same course. All the course materials were the same from last time, except that this time I’d learned so much more from it. The reason was very simple: when I was an undergraduate, I took the class because I needed it for my degree; this time I took the class because I wanted to learn from it. I started to realize how a simple change in attitude can affect our rewards.
I think everyone who learns evolution is familiar with Red Queen Hypothesis. The Red Queen said, “It takes all the running you can do, to keep in the same place.” I’d heard the concept over and over again in different lectures, until it brought a new meaning to me in one excellent seminar. The speaker applied the Red Queen Hypothesis onto human: “We have to keep changing in order to maintain at where we are.” I think it is so true.
In every lab, no matter molecular or field work, there are many things to learn other than the techniques, such as how to prepare a field trip, how to organize field workers, how to schedule lab work so that we have something to do while waiting for the PCR, how to avoid contamination, how to keep things in order, etc. People who think they’ve learned everything will stop learning. People who think there are more to learn will have the motivation to continue.
If one eventually learned most of the things and finally became an expert in certain field, doing similar thing everyday may be kind of boring. A little bit of changes may keep us motivated. Changing in living environment or in career direction will give us more things to learn. Changing is scary, but it is a progress of life. We will learn the most when we put ourselves in another group with different specialities. That’s why I think what I need are the right attitude for learning, and the courage for changing.
These are what I have been thinking since I started to join the XTBG program. Everything here is so new to me, so everyday is a new challenge. I don’t know how persistent I can be to maintain the right attitude and the courage. It is always easier to say than actually doing it. But so far, I am really enjoying the progress.