| by Gaen Murphree


Summer 2019 Eggleston Lab onboard the R/V Folger. (L-R Clara Loftis ’21, Ellie Broeren ’22, Evan Fedorov ’21, Erin Eggleston)

Biology professor Erin Eggleston is driving her crew of research assistants north on Route 7 toward a water-sampling site on Lake Champlain when she suddenly slows the vehicle, veers right, and says, “Red-tailed hawk.”

And there it is, perched on a power line alongside the road—a large raptor, patiently surveying the surrounding fields for prey.

As a molecular microbial ecologist, Eggleston more typically trains her eye on far smaller organisms. Yet her roots in observing the natural world—creatures large and very, very small—run deep.

“The classic Eggleston family scenario is all of us in the car, driving on the Alaskan Highway, and just then the brakes slam on and we pull over on the side of the road because there was an owl in a branch, and did we see it? Or, there was this hawk, or that kingfisher, and ‘Did you see it?’ You stopped and you got your binoculars out and you’re just pulled over on the side of the road trying to spot the bird of the moment.”

Eggleston grew up in Alaska in a family that loved hiking, rafting, camping—and birding. While her upbringing gave her a love of nature on a grand scale (glaciers the size of Rhode Island; eagles as plentiful as pigeons; the country’s tallest peak and longest nights), she discovered her love of microorganisms as an undergraduate.

“A friend of mine was working on this project involving microbes that cycle arsenic, and he was like, ‘You should try working on this.’”

The project focused on arsenic contamination in apple orchards (caused by pesticides).

“It was this sort of bioremediation idea of, could you enrich for certain microbes that would make the arsenic less toxic? They use it for their respiration. The same way we use oxygen, they use arsenic.”

Around that same time, she took a class on extremophiles: microorganisms that live in such seemingly inhospitable places as Antarctic sea ice, volcanic hot springs, saline pools, acidic mine drainage.

The combination of these two experiences, said Eggleston, “got me in.”

What fascinates Eggleston most about microbes?

“Just their versatility. That they aren’t limited. The metabolic capabilities of microbes are extreme. We are limited to breathing oxygen, but they can respire using heavy metals like uranium. They can also use really diverse carbon sources. We can eat things like bread, but they can use organic solvents.”

Eggleston is currently researching cyanobacteria (commonly known as “blue-green algae”), the bacteria phylum responsible for toxic blooms on Lake Champlain and other waters.

Given enough heat and enough phosphorus (or nitrogen), this naturally occurring bacteria can suddenly spread across a body of water like greenish paint. Already this summer, various beaches along Lake Champlain and smaller Vermont lakes and ponds have been put on high alert and closed temporarily. Two dogs have died. The Vermont Department of Health reports that over the past two decades such toxic blooms have been increasing.

“We’re just trying to understand who’s there and what they’re doing,” said Eggleston. “There are just a number of basic questions that we don’t have answers to yet.”

In this summer’s research, Eggleston wants to identify the diversity of cyanobacteria and of a category of viruses called “cyanophage” in Lake Champlain and other Vermont waters, while also examining the role bacteria-virus interactions play in bloom toxicity and overall bloom dynamics.

Cyanobacteria occupy their own phylum within the bacteria domain. They are among the most plentiful and most important organisms on earth. Some three billion years ago they began making oxygen from photosynthesis, thus making possible life on earth—as most of us know it. Yet they remain a mystery. Scientists have described over 2,600 species of cyanobacteria and expect to find as many as 6,000 to 8,000.

Viruses, Eggleston explains, are “bio-entities” that lack the necessary components to be considered living organisms. Instead, they’re a kind of microscopic parasite: attacking organisms, taking over cell mechanisms to replicate their own genetic material, and then bursting out to parasitize still others.

Some cyanobacteria are toxin producing; some are not. This summer’s big question: As the cyanophage invade a host cyanobacteria can they also transfer toxicity genes to nontoxic cyanobacteria? What role do they play in bloom toxicity?

These questions, said Eggleston, have not been studied.

“The vast majority of life on earth is not visible to the human eye. And until recently there was no way to assess what was there,” said colleague Jeremy Ward, a recent department chair who shares lab space with Eggleston and who cotaught a J-term field course examining coral reefs in the Bahamas. “Erin’s tackling very difficult questions, about the smallest genetic systems out there. We know very little about what the microbes are doing, and compared to that, we know nothing about the viruses.”

Eggleston seamlessly integrates her research into her teaching, observed Ward, and brings an approach to teaching that’s invigorating.

“Biology is empirical, right? You’ve got to do it. So lecturing isn’t always the most effective way to teach a lot of that stuff. Erin doesn’t lecture very much. Her approach is inquiry based. Students have to talk to each other, they have to think about it, they have to come back to it, they have to try it again.”

Eggleston’s field is revolutionizing how we understand the world, especially as advances in genetic sequencing (made more accessible by a concurrent drop in price) reveal patterns in how living things are organized that defy earlier systems. The fact that we still commonly refer to cyanobacteria as “blue-green algae” is a holdover from an earlier time.

“When I was in high school,” said Eggleston, “we learned about the ‘Five Kingdoms of Life.’ That’s no longer true for my students. The Five Kingdoms of Life are out; now we have three domains.”

On this new tree of life, “animals” are demoted from a sturdy limb to an outer twig, right next to slime mold. It’s enough to make you sympathize with Renaissance thinkers, suddenly forced to consider that the earth revolved around the sun.

Over an hour of driving later, we pull up to a pier alongside the North Hero Bridge. Eggleston also takes water samples on other spots on Lake Champlain and on Lakes Hortonia and Bomoseen, sharing resources and data sets with a University of Vermont collaborator.

The crew unpacks the gear and gets to work.

“I really like the fieldwork,” said summer research assistant Ellie Broeren, a rising sophomore. “You’re using your body, you’re on the lake, and you’re doing something that’s intellectually engaging.”

Looking off the end of the pier, cyanobacteria colonies are visible to the naked eye, tiny green dots floating in the water. Along the north side of the pier, the clusters are more intense, painting the lake with swirls of green. Broeren and fellow research assistant Clara Loftis ’21 clamber down the rock embankment to get samples from there as well.

Seen under a microscope, each dot is made up of chains of bacteria clustered together to form a sphere, like a brownish-greenish version of a dandelion head right before it blows away.

Most days, Broeren and Loftis explain, are spent in the lab filtering water samples to get the right collection of viruses and microbial critters; creating slides stained with a fluorescent dye so that they can count relative numbers of viruses, bacteria, and larger microorganisms under a microscope; and preparing samples to be sent to a DNA sequencing facility (a multistep process that requires a number of chemical and other processes).

“I was really drawn to learning something new,” said Loftis. “As a neuroscience major, I don’t work with bacteria and viruses; I don’t have to take ecology and evolution. But being in Erin’s lab I get to learn some of those concepts, in a hands-on style.”

Research assistant Evan Fedorov, a rising junior in molecular biology and biochemistry, is also working on a separate project (a collaboration between Eggleston and a Dartmouth colleague), examining the archaeon extremophile Sulfolobus islandicus.

“Professor Eggleston is just a great mentor,” said Fedorov. “She’s always very insightful; knows so much about the topic; so all my inquiries are just answered. Whenever I’m trying to have a new idea or want to take the project in a new way, she’s open to listen. When I gravitated to the archaeon project, she allowed me to pursue that more fully.”

Said Ward: “There is no better teaching tool than saying to a student, ‘Listen, this is incredibly important, and you’re going to be one of the first people to ever describe it.’ I mean, no one wants to be the 47th person to describe something, right? This field is so new, there’s a tremendous amount of opportunity. So these students really get a chance to be the very first people to talk about some of this stuff. And I think that’s powerful.”