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In early July, about an hour after sunrise, a cloud-covered sky greets the Capricorn research vessel and its 20-something passengers as it chugs through Bogue Sound on its way to the open ocean. After passing Fort Macon through Beaufort Inlet, the chop increases, aggressively tossing the boat up and down like a toddler with a toy in the bathtub.

The 48-foot vessel is notorious for its sway. That’s why Joel Fodrie, former director of the UNC Institute of Marine Sciences (IMS), always recommends guests take Dramamine before coming aboard — “even if you’ve never gotten seasick in your life,” he says in a text message the night before.

Meanwhile, Alecia Septer casually leans against the side of the boat, a small smile on her face as the wind whips her hair.

“I love the taste of salt in the air,” she says.

You’d never guess the Carolina microbiologist grew up in landlocked Ohio, where her earliest memories of open water come from a backyard baby pool. She looks perfectly at ease on the Capricorn, even though she didn’t see the ocean until her 20s.

As the sun wrestles its way out of the clouds, the seas slowly settle. Still, guests spend most of the day white-knuckling anything they can grip. Captain Stacy Davis, an Outer Banks native who grew up in a family of commercial fishers, offers reassurance: “There’s no need to be worried — unless I’m worried.”

Undeterred, the crew moves ahead with its routine: trawl for bait, prepare 100 hooks, set a 1-kilometer-long line, and wait.

An hour later, it’s time to check the line. Septer watches as IMS technicians pull the hooks aboard one by one. Most come back empty. Then someone shouts, “Shark on!”

A five-foot-long hammerhead emerges from the water. The team quickly removes the hook and places the animal in a water-filled trough. Researchers record its species, sex, and measurements before attaching a tag. Then Septer swoops in to do something unexpected: She pinches its cheeks. A clear, viscous fluid oozes from tiny pores along the shark’s head.

This specialized gel helps sharks navigate and detect the faint electrical signals produced by the heartbeats and muscle contractions of nearby prey. Septer wants to understand the bacteria living inside it and what role they might play in the shark’s microbiome.

“This gel is pretty amazing,” she says. “Even after freezing and heating, the bacteria in it continue to survive. And we’re finding genes that suggest they produce beneficial health compounds for the host.”

But to understand why Septer is squeezing sensory gel from sharks, you have to go back two decades to a time when she was interested in a very different marine animal: a tiny squid.

Strange similarities

The homepage of Septer’s lab features a cartoon drawing of two bacteria, one wielding a sword like Inigo Montoya from “The Princess Bride.”

“Anytime an animal is born or a plant emerges, it’s a new opportunity for microbes in the environment to colonize it,” Septer explains. “There’s usually some sort of competition for nutrients and space within that new niche. I’m interested in how bacteria compete when they’re colonizing a host. So, basically, how bacteria kill each other.”

Her goal is to understand how bacteria eliminate competitors without harming their host, knowledge that could one day help researchers develop new therapies for infections in humans and other animals.

Septer began studying these relationships during her PhD program at the University of Georgia, where she maintained a colony of Hawaiian bobtail squid. These tiny, speckled animals have partnered with a single species of glowing bacteria for more than 40 million years, making them an ideal model for studying how microbes colonize and coexist with their hosts.

The bacteria communicate through chemical signals that coordinate light production. But when grown in the lab, they don’t glow nearly as brightly as they do inside a squid. And Septer wanted to know why.

Her research revealed that environmental factors such as iron availability, oxygen conditions, and metabolism all influence the bacteria’s brightness, suggesting that their light production carries much more information than scientists once realized.

The bacteria live in tiny pockets within the squid’s light organ called crypts, which contain a viscous fluid. Every morning, the squid expels 90% to 95% of the bacteria from its crypts, forcing the remaining population to rapidly grow and refill the space before nightfall.

That work unexpectedly laid the foundation for Septer’s next research question.

Sharks and rays possess sensory organs called Ampullae of Lorenzini, which are filled with a conductive gel. The structure and chemical environment of those organs resemble the squid crypts Septer spent years studying. So, when IMS postdoctoral researcher Chelsea Black approached her with the idea of investigating the shark microbiome, they decided to focus on this gel, an understudied substance found in all sharks.

“Marine animals have been important model systems for a long time — sea urchins and sand biscuits for studying fertilization and embryology, and squid for neurobiology,” Septer says. “I’d always been interested in looking at the shark microbiome, but I needed someone sharky to help me. Chelsea is a shark ecologist and could support that part of the project.”

An ocean of opportunity

Before Septer could study the microbes living in shark gel, she faced a practical challenge: obtaining samples from healthy animals. Fortunately, UNC-Chapel Hill had access to one of the nation’s most data-rich shark research programs.

IMS launched its shark survey in 1972 and now oversees the longest-running shark survey in the United States. Every other week from April through October, the Capricorn heads up to seven miles offshore to bait more than 100 hooks in hopes of temporarily catching and studying these Apex predators. Over the course of the program, IMS has surveyed more than 11,000 sharks, documenting long-term changes in populations and species distribution.

“This project wouldn’t exist without IMS,” Septer says. “The survey provides the best opportunity to get the samples we need. It’s a huge team effort.”

A few days before their first shark survey, Septer had one lingering question for Black: “Are the sharks going to care if we, you know, give them a little squeeze?”

Black, who had already spent a decade studying Atlantic shark species, didn’t think so.

She was right.

They discovered that gentle pressure near the nose or behind the eyes releases enough gel for sampling and causes no apparent harm to the animals. Septer and her lab are preparing an open-access research paper to share this knowledge with scientists interested in conducting similar studies.

“The pore patterns and amount of jelly in the canals leading to those pores vary by species,” Septer says. “So we’ve had to figure out the best place to squeeze on each one.”

A living pharmacy

The gel is collected using sterile tubes, placed on ice, and transported back to Chapel Hill for processing. So far, Septer and her team have found that multiple bacterial species inhabit the gel, but a core group appears consistently across samples.

Septer’s lab recently discovered that one bacterium can inhibit the growth of another, a clue that these microbes may produce antimicrobial, antifungal, antiparasitic, or antiviral compounds that help protect the shark’s sensory organs from infection.

“The bacterium has evolved to make these antimicrobials that don’t hurt the host,” Septer says. “Studying bacteria like this that have been evolving for billions of years could help us create new antibiotics.”

For now, Septer and her collaborators are continuing to map the microbial communities hidden inside shark sensory gel and identify the compounds they produce. Every IMS survey brings new samples and new questions.

The answers could eventually contribute to treatments for human disease. But they also reinforce a lesson marine scientists have learned time and again: Some of nature’s most powerful innovations are hidden in unexpected places.