A team of six Henderson State University biology students are on a mission to examine and analyze mysterious microbes found deep underground in a unique Tennessee cave. For the past two years, they have been using metagenomic DNA sequencing to identify microbes from a “petroleum pond” found in the cave.
In 2019, Michael Ray Taylor, chair of Henderson’s Department of Communication and Theatre Arts, explored the “highly unusual” cave system, known as “Secret Squirrel Cave” to protect its location.
Taylor has explored caves in the southern United States for 35 years and written about his adventures for a variety of national publications.
Taylor had heard about an unusual “petroleum pond” in the cave, and he discovered some unusual features during his exploration. He collected nine samples and brought them back to Henderson for analysis.
Dr. James Engman, a professor of biology at Henderson, had led a study at Blanchard Springs Caverns in Arkansas. He adapted the research techniques from that study to begin a new research effort focusing on the samples collected by Taylor.
Students Kaylie Wheeless, Lauren Camp, Aspen Huseman, and Maya Robles are the original members of the team. With Camp and Wheeless graduating this year, Rocio Alferez and Mitti Fairchild have joined the research group.
Camp is from Maumelle and previously played volleyball at Henderson.
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When explorers initially entered Secret Squirrel Cave more than 10 years ago, Engman said they considered it a “typical” cavern. But recent exploration and mapping has revealed previously overlooked passages that have now been mapped to more than 15 miles with many unusual features and formations.
Henderson’s research team has focused on the samples from the section known as the “Petroleum Passage” for its strong odor of petroleum.
Engman said unusual dark patches surrounded by colored rings of sediment were discovered on the sandy bottom of a large pond in the passage. He said the patches, called “mini-vents,” occasionally release bubbles of an oily material that rise to the surface and burst, releasing the petroleum odor.
At times, this passage has dense populations of larval cave salamanders and cave-adapted millipedes that are not expected so deep within a cave where the products of photosynthesis are “scarce to absent.”
The cave appears to have been at least partly formed by the action of sulfuric acid, rising from below and dissolving the limestone, rather than the typical means of cave formation involving mildly acidic rainwater from the surface, Engman said.
“This process, which leaves behind impressive gypsum formations, is known from some of the most famous caves in the western U.S., but is not well-documented in the eastern U.S.,” he said. “Such caves have been proposed as possible models for life in subsurface environments on Mars.
“The science in this project is really fascinating, and we are expanding our understanding of extreme environments,” Engman said. “For me, though, the most exciting part is getting undergraduate students involved in discovery and fieldwork that they get so excited about.”
To date, the students have identified 593 different microbes. While some are common, and would be expected in most caves, others are unique and have the ability to metabolize methane, sulfur compounds, ammonia, and hydrocarbons, Engman said.
The student team now seeks to conduct its own exploration of Secret Squirrel Cave to continue and enhance its research. To provide the group with caving experience before actually exploring and conducting research in Secret Squirrel Cave, Taylor took them on a three-day excursion in August to a large cave within Fall Creek Falls State Park in Tennessee to learn caving techniques.
The team hopes to explore Secret Squirrel Cave and collect more samples later this year.
Camp, a senior from Maumelle, said she was “extremely nervous” at first.
“Once I got inside the cave, I was completely taken away,” Camp said. “It was beautiful, and nothing like I had ever seen before. It was truly amazing to see what most don’t get to see.”
Maya Robles, a sophomore from Katy, Texas, said she had “no idea” that she would become involved in such an exciting project.
“Our recent caving expedition jump-started my desire to seek adventure,” Robles said. “As we were walking through the tight passages, enormous rooms, and sketchy climbs, I never wanted to turn around.
“After my experience in the cave and time spent with my team and the other cavers, I hope to continue having adventures like these. I am so excited for these years to come.”
Kaylie Wheeless, a senior from Cedar Hill, Texas, said, “It felt like time had paused when we entered the cave.
“As biology students, we couldn’t help but wonder what microorganisms we would find if we were to take a swab from each fragile cave formation we passed,” Wheeless said. “I thought it was interesting that as we climbed, hours would pass and I’d have no idea how it could possibly have been that long.”
Aspen Huseman, a junior from Cabot, said she was “at a loss for words” in trying to describe her caving experience.
“There is no true way to depict the experience of caving until you get to actually do it,” Huseman said. “Coming to Henderson, I never expected to get opportunities like this. It was one of the scariest, most adventurous, thrilling, and most amazing things I have done.”
Mattison Fairchild, a junior from Conway, described the adventure as “surreal.”
“I have been in a cave before, but this was my first experience in true caving,” Fairchild said. “I enjoyed the stunning sights inside, but I also enjoyed the physical challenges that the cave presented. This was one of the most amazing experiences.”
Rocio Alferez is an international student from El Salvador. She was impressed by the cave formations, the size of the room, and the cave crickets.
“You see huge mountains of breakdown, followed by pitch darkness, and wonder, ‘can I really climb this?’” Alferez said. “The curiosity and intrigue of seeing what’s on the other side makes you keep going further.”
Huseman added, “I’m hoping the team and I will soon have the opportunity to use our new caving skills to explore the Secret Squirrel Cave and collect more samples and data from our research site.”
The research team’s work has been presented at several professional meetings, including the Council on Undergraduate Research “Posters on the Hill” Symposium, and the Arkansas INBRE conference.
Wheeles presented at the annual convention of the National Speleological Society in July and received the award for Best Student Paper.
Engman described the project as the “most exciting” he’s been involved with during his tenure at Henderson. It has a growing list of collaborators, including: an analytical chemist from the stable isotope lab at the University of Arkansas; a salamander expert from the University of Alabama; and a karst geologist from Tennessee.
“Mike’s (Taylor) role in this project cannot be underestimated,” Engman said. “A caver for 42 years, he is closely connected with not only the caving community, but with the groundbreaking microbiologists who have studied the most amazing cave systems we have.
“His many books on caving have received much critical acclaim and awards. He may be the most prominent caving journalist there is.”
Engman emphasized the opportunities undergraduate research provides for students.
“I believe that undergraduate research is one of the most important things to get students involved in,” Engman said. “It increases their competitiveness for admission to graduate and professional programs, hones critical thinking skills, and can give them experiences they never dreamed of.”
The project is funded from several sources.
Robles and Wheeless are McNair Scholars and receive financial support for their work from the TRIO program. Wheeless received a State Undergraduate Research Fund grant last spring.
Camp received a NASA/Arkansas Space Grant Consortium, and Huseman was awarded a Scholars Fellowship grant from the National Cave and Karst Research Institute. Robles is waiting to hear the decision on her grant submitted to the Explorer’s Club.
Lauren Camp @LAURENCAMP__We explored microbial samples of a cave system in Tennesee. We identified unique bacteria including species that metabolize sulfur and methane coumpounds. The results provide insight to the previously suggested model for life in subsurface Mars. #POH2020 #POHGoesVirtual 5:02 PM ∙ Apr 21, 202032Likes8RetweetsMy experience caving for the first time was incredible. I was extremely nervous before we began. However, once I got inside the cave, I was completely taken away. It was beautiful and nothing like I had ever seen before. This was also my first time getting to socialize with “cavers.” I had always heard that cavers are such good people, and that statement couldn’t be more true. I was encouraged the whole way. Since my trip, I have recommended caving to everyone I have spoken to. It was truly amazing to see what most don’t get to see. — Lauren Camp
My experience caving for the first time was incredible. I was extremely nervous before we began. However, once I got inside the cave, I was completely taken away. It was beautiful and nothing like I had ever seen before. This was also my first time getting to socialize with “cavers.” I had always heard that cavers are such good people, and that statement couldn’t be more true. I was encouraged the whole way. Since my trip, I have recommended caving to everyone I have spoken to. It was truly amazing to see what most don’t get to see. — Lauren Camp