The value of slime: university research at SURF probes cave silver biofilms
The biofilms that line the walls in a few underground areas at SURF are home to a unique set of microbes with potential for future study and possible applications in medicine.
Slime is a general point of fascination for kids of all ages – it’s on the shelves of toy stores; it comes stuck to the walls of plastic gumball machine containers; and if you grew up rural--it’s the nasty green moss skimming your local stock pond that’s perfect for starting a fight with any hapless sibling in throwing range.
In biology, certain types of slimes called biofilms are of particular interest to researchers.
Biofilms are built by communities of microbes, bacteria, and fungi. They serve as a kind of protective shelter and home for various types of microscopic life. The lifeforms inside biofilms often exist in symbiosis with each other—the work of one benefits another and vice versa.
It turns out biofilms are everywhere. They’re the slimy surface on the rocks at the edge of a lake. They form on deep oceanic shipwrecks like the Titanic. They also exist underground—as thin, glistening layers that occasionally coat the walls of both caves and mines when the humidity and condensation levels are just right. These subterrain biofilms are commonly called “cave silver.” The name stems from the iridescent nature they exhibit when illuminated by a flashlight or headlamp.
Dave Bergmann, a professor of biology at Black Hills State University, aims to unravel the mysteries of these unique biofilms—and his work centers on unique types of cave silver found only at the Sanford Underground Research Facility (SURF).
Bergmann’s focus on the biofilms of SURF includes those found both at depths of 800 and 4850 feet. “These biofilms exhibit a significant specificity according to depth, which is fascinating,” he explains. The composition of microbial communities varies markedly between different levels, suggesting a complex interplay between geological and environmental factors. Their source of nutrients is not entirely clear, nor are the microbes underground often the same as those found on the surface. Unlike a cave, that may be in place for thousands of years, SURF is inside a former gold mine, and a relatively new spot for these microbial colonies to form. Bergmann says the source of these biofilms and their relationship to the facility's depth is a point of future study.
Bergmann says further study and research should also be focused on the potential for these biofilms to yield new antibiotics. “The genera Pseudonocardia and Crossiella found at SURF may warrant further investigation for antibiotic production,” he states. These organisms may possess unique metabolic pathways that produce compounds with antimicrobial properties. Bergmann emphasizes that some microbes require specific environmental cues to trigger antibiotic production, indicating the importance of further study for their interactions within biofilms.
As part of this effort, he is working on a method of sampling that has potential for culturing difficult-to-isolate microbes in a needle-point-sized sample space. This allows researchers to examine how one type of microbe might interact with another in the vicinity. “We need to sample these microorganisms at a very small scale to better understand their interactions and potential applications,” he emphasizes.
Bergmann’s work is also focused on the education of his students. He champions hands-on experience in the field as crucial for fostering a deep understanding of microbiology. “You don’t really appreciate these habitats until you actually see them. Practical questions arise when you witness these organisms thriving in such extreme conditions,” he notes. Bergman says when his students visit SURF to sample cave silver they learn essential microbiological techniques, including field sampling, DNA manipulation, and genomic analysis, providing them with valuable skills for their future careers in science.
Bergmann’s work is part of a range of biological studies at SURF. In separate research, the Deep Mine Microbial Observatory (DeMMO) looks at microbial life in groundwater and other places at SURF for insight into lifeforms in extreme conditions on other planets, medical uses, and other applications. South Dakota Mines researchers have pioneered work on microbes sampled from SURF for use in enhanced carbon sequestration. Separate teams of university researchers at Mines are also looking at water chemistry at SURF and its relation to microbial life underground and additional research on biofilms, 2D BEST, a South Dakota EPSCoR / NSF funded project.
