The Kids' Science Challenge

Katrina Edwards is a Professor of Microbiology at the University of Southern California, who teaches microbiology classes as well as geobiology classes. She also runs a research laboratory, and the projects that she does are at the bottom of the oceanic realm.

What do you study?

I’m a microbiologist, and that means that I study the smallest creatures on our planet. Although they’re the most populous creatures on our planet, we really can’t see them with the naked eye, and that’s why they’re called microbes. And microbes are fascinating creatures because they can do so many different things compared to what we can do. We, basically, have two functions. We eat carbon, and we breathe air, and that’s what we do for a living, and all mammals are like that.

In contrast, microbes can do all sorts of crazy things, like eating iron and respiring nitrogen or eating carbon and respiring iron oxides. And so, studying them in an environmental context is what I do as a researcher.

The American Society for Microbiology (ASM)
is the oldest and largest single life science membership organization in the world.

Can you tell us more about microbes?
Well, microbes are the most ancient life form on our planet. We all evolved from microbial forms to what we are today. So, microbes are single-celled organisms. The whole tree of life is encompassed within microbiology. Really, the only defining feature is that they’re all too small to see with the naked eye, although there are, of course, exceptions to that rule, as there always are.

Microbes are amazing also because they inhabit simply every single corner of our Earth. We think of ourselves as occupying most of the planet now, but there’s actually a lot of places where people are not, and microbes are simply everywhere. In fact, we have a hard time defining where they are not. Where my research takes me is below the bottom of the ocean. And so, we’re trying to investigate the diversity of microbial life hundreds of meters, if not kilometers, below the ocean’s floor. And so, microbes can persist to all depths as long as the – the temperature is okay for life. That's why I study microbiology, because of how amazing microbes are. They can just live anywhere, do anything, and they’re just really fun to work with.

We are still really learning about what microbes can do, but what they are really good at doing is regulating all of the biogeochemical cycles on our planet. So, the carbon cycle, for example, is completely regulated by microbial life on our planet: the iron cycle, the sulfur cycle, and it just goes on and on. Microbes are the ones that are keeping the planet in its balanced form. So, when you think about topics like global warming and how that’s going to affect life in the oceans and life on land, it’s also important to think about how that’s going to affect microbial life because they’re the stewards of our planet, and if we impact them significantly, it’s going to feed back and impact us significantly as well.

Another really amazing fact about microbes is how populous they are – in and on us. There’s actually an order of magnitude more microbial cells in and on you than there are cells of yourself. And so, they’re really doing a lot of functionally good things for you. We’re used to thinking about microbes as germs, but they’re not, really. That’s just one variety of microbe that actually has bad effects on human health.

Most microbes have good effects on human health. For example, we couldn’t digest food without microbes. Microbes are in there synthesizing vitamins that we need to live and to – to prosper. And so, they’re doing really important things for us, and we – we – we need to be mindful of the microbial biome whenever we’re doing things like bathing or using antibiotic soaps. Those are not necessarily the best thing to be using because we need our microbes to maintain our health.

Tell us about your research.
So, my research takes me to the bottom of the ocean. And what I like to look at is how microbes control alteration of oceanic rocks. So, the alteration of rocks on our planets is also one of the major contributors to the biogeochemical cycles, including the iron cycle, the carbon cycle, the sulfur cycle, and just goes on and on. And so, that’s one realm where microbes really play a role, and we don’t know very much about how they do it.

I like to use the analogy of dentistry. We all know that if you don’t brush your teeth, or even if you do, you sometimes get cavities. These are caused by microbes that are drilling into and eating your teeth. At the bottom of the ocean, where we have, essentially, the molars of the world exposed along mid-ocean ridges, microbes are doing the exact same thing. They’re transforming the basaltic rock that makes up 70 percent of the planet, and they’re transforming it into something else. So, microbes are actually making material exchanges and exchanging elements at the same time. And so, that’s why it influences the biogeochemical cycles, and that’s really what I’m trying to understand.

What sort of tools do you use in your work?
I got my start in studying microbial life and how it’s affecting the alteration – basically, the "tooth decay" of the solid earth at the bottom of the ocean – by studying seafloor rocks and minerals at the bottom of the ocean. And so, that’s what I studied for the first part of my scientific career. And to do that, we actually have to use some pretty sophisticated technologies that include submersibles or manned vehicles that go down into great depths or using remotely-operated vehicles, or ROVs. And these are robots that you operate from a ship, and they go down by a long tether from the ship and explore and sample and do whatever you need to do at the oceanic floor. And so, these are amazing tools that we have available to the scientific community to address deep sea scientific questions.