Ashley's Biggest Takeaways:
- In 1878, German surgeon, botanist and microbiologist, Heinrich Anton de Bary, first described symbiosis as the living together of two or more different organisms in close physical intimacy for a longer period of time.
- These relationships can be beneficial, detrimental or commensal, depending on the organisms involved.
- Microbial symbiosis research holds great potential to contribute to sustainable energy production and environmental health.
Featured Quotes:
When I was looking for a topic for my Ph.D., and I wanted to do marine biology, and I definitely was not interested in microbiology, period, my Ph.D. advisor said, 'I'm working on these little worms. They don't have a mouth or a gut, and they live off of symbiotic bacteria.' And I still wasn't so sure. But then he described that their main distribution areas are in tropical and subtropical areas, and that I could go collect them. And that was definitely a motivator.What motivates me now, though, is that it's been such an incredible time in microbiology. Now we see how widespread beneficial interactions are, and we have the tools, through sequencing and imaging, to understand them. Just [about] every conference I go to there's a new method [that could be used or is being used] to look at an uncultivable microorganism, which is what most of these organisms are.
I started working on symbioses in 1992 as a postdoc. I joined the lab of Colleen Cavanaugh at Harvard University, who was one of the first researchers to work on the symbioses between hydrothermal vent tube worms and their symbiotic bacteria. And when we started our first question was, 'Who are the symbionts?'
Using 16s, I [would spend] a year and a half to sequence a single gene to get that information, then another year and a half trying to label it with fluorescent probes to show that it was really the symbiont, and then spend what felt like years trying to get the paper out. That's also why I emphasize how exciting it is that we now have the tools to look at 100s of individuals with 1000s of genes.
We're not hypothesis driven. I actually really, really like to emphasize that we're discovery driven. What we do is discovery-based research, and sequencing is nothing else but discovery-based research. And then we look at what we get in terms of results. We get predictions, and then we dive in deep to see, are those predictions correct? But I'm a big, big defender of discovery-based research, because there's such an emphasis on you have to have a hypothesis. But I no longer agree with that.
So you take whatever organism you're interested in and you homogenize it, and you sequence the hell out of it—at least, that's what we always say we do. But then we try to save 1 piece of the host to use for actual visualization through microscopy. And the reason that it's so important for us to have these paired studies is because we do see a lot of variation from individual to individual.
So what we do when we collect our shallow water hose, and I really encourage anybody who goes diving or even snorkeling or just wading out in knee deep water from in the Mediterranean and the Caribbean [to try]—in fact, even off of the coast of Florida, we recently collected them—and what we do is we take some sediment, and we put it in a bucket. Then there's a very fancy method called decantation, which means you just stir the sediment around. The worms (the hosts) are lighter than the sediment, and you pour [the sediment] through a sieve, and then in your sieve, you've got lots of animals. They're called myofauna because they're small, and they're in the sediment.
And those that are white, those are our hosts, and they're white because they have sulfur oxidizing bacteria. They have sulfur vesicles and PHA and that makes them look white. So that, of course, is great fun. We're planning a trip right now to the Great Barrier Reef, and we're doing it right this time. We're going to go there in the Australian summer, [when] it's really rainy and nasty in northern Germany.
Then the other obvious collection is when we go out with research vessels and collect our animals in the deep sea with remote operated vehicles or submersibles. And that's a totally different sampling experience. It's crazy, because you spend 6 weeks at sea, but you can't get into the water. But it's also another type of expedition that I love.
I mean, in the beginning, we were agnostic in that we just said, 'Whatever we find is fine with us.' What we care about is that we find it in more than 1 individual. If you're looking for a symbiont that hasn't been described yet, then one of the giveaways is that it's even if it's in low abundance, if it's regularly present in every single individual, or almost every single individual you look at, there's a good chance that it really is meaningful.
That said, we've just started finding some very, very cool bugs that we think might actually be pathogens related to Wolbachia that can cause changes in sexes in insects. They're super low abundance. We can barely find them, but they're so interesting. They have 100 KB genomes. They're teeny, tiny, and so we've started looking at them as well.
So generally, we're agnostic, but we know we should be [looking for] chemosynthetic bacteria. Photosynthesis is you use the energy from the sun to fix CO2. In chemosynthesis, you're using chemical compounds, like methane, like hydrogen, like hydrogen sulfide. Bacteria—and only microbes—can use that energy with an electron acceptor, often O2, to gain energy and then to fix CO2. So it's there are only 2 forms of primary production on this planet, one is photosynthesis, and the other is chemosynthesis. So that's it in a nutshell.
Working with my team, I really have to say, they're young, and they keep me young, and it's just incredibly rewarding. To see them grow, to see them go off and and get jobs and become academics, or go to industry or to non-governmental associations. It's like you're nurturing 100s and 100s of your own kids and and and getting to work with these super smart kids—I'm sorry, they're grown ups. But that's I find one of the most motivating and wonderful experiences of my career.
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