- watching the evolution of mutualism from its origin in real-time, in the laboratory
What do we do?
From the venom of a snake to the intricate structures of some orchids, the biological world is full of interesting traits that result from the interactions of one species with another. Some of these interactions are antagonistic: species compete for resources, kill and eat each other, or infect and harm hosts. Other interactions are - at least on the surface - more cooperative: plants and insects exchange food for reproduction, cleaner fish keep their hosts parasite-free in exchange for food. We are interested in understanding how evolution affects, and is affected by these interactions between species. But we don't study this by looking at fish or flowers or insects. We study microorganisms. These are single-celled species that are so small they cannot be seen with the naked eye.
Why study interactions between microorganisms?
It might seem strange to think that something so small could be a predator, cooperate, or have adaptations as beautiful and intriguing as the shape of an orchid, but they do. In fact, microbial communities are extraordinarily complex and they are everywhere. They live in hot springs at yellowstone, in underwater volcanos, on every surface, in the air, in the soil, and even in your body. There are more microorganisms in your body than there are human cells - a lot more. Not only are there large numbers of microbes, but there are thousands and thousands of species living together. Some are known to be predators or prey, or pathogens. Others are known to cooperate. However, we are far from having a complete picture of all the interactions occurring, their effects on communities, and how they affect species evolution. We need to understand this for many reasons. One is that there are actually far far more microbial species than there are macro-bial species. If we ever want to find or confirm 'general' biological principles about species interactions or evolution, we must consider microbes. Another reason is that we are becoming more and more aware of complex interactions between the microbes and the species we can see, including ourselves. In many of these cases, (e.g. the microorganisms in our guts) it is not just one species, but an entire community of species that is involved.
Microorganisms also have features that make them good tools for studying evolution and ecology. We can use them to test hypotheses and observe evolution with rigor that would be extremely difficult or impossible in many species that we can observe with the naked eye. Microorganisms replicate quickly, are readily manipulated in the laboratory, have large population sizes, and can be frozen and kept in suspended animation in the lab. These properties allow us to observe thousands of generations of evolution in the laboratory, in controlled environments, and to directly compare the genes and traits of ancestors and evolved populations in the same experiment.
What do we want to know about their evolution?
We focus on studying known interactions between microorganisms, although it would also be interesting to learn about new associations. Sometimes we use the interactions as tools to test broad hypotheses about how mutualistic or predator-prey interactions evolve. Sometimes we want to really understand how a particular interaction works. We want to know how species interactions originate and what happens in the early stages of their evolution? Do cooperative interactions between species evolve similarly to antagonistic interactions? What kinds of adaptations do microbes acquire in response to other species? How repeatable is the evolution?
What species are we studying?
Most of our work involves an interaction between a bacteria and an archaea. Both species are capable of growing alone, but we put them together in an environment where they must cooperate to survive. The bacteria provides food to the archaea as a byproduct of its metabolism. This byproduct can inhibit the bacteria if it ever accumulates to high concentrations.. By eating the byproduct, the archaea ensures that this toxic situation never occurs, allowing both species to flourish in conditions where neither could on their own. I have also worked with Myxobacteria. These are species that swarm around in soil searching for other bacteria that they consume as prey. They also cooperate with one another in their hunting, and when they starve.