Moldies but goodies: Smokies’ slime molds climb the charts in groundbreaking research
When a heavy rain washed into Paul Super’s garage last month, soaking a couple of bags of freshly-purchased mulch in the process, it triggered a dormant slime mold in the mulch to spring to life in a bright yellow ooze, much to the delight of his four-year-old son.
“When people came to visit, he would say ‘You want to come to the garage and see the slime mold?’” Super said. Super, a scientist in Haywood County for the Great Smoky Mountains National Park, was just as pleased with their pet slime mold as his son, although its appearance was a bit like bringing coals to Newcastle. Super is spearheading a global survey into the largely mysterious family known as slime molds for the National Science Foundation.
The Great Smoky Mountains National Park is ground zero for the research. More than 200 slime mold species live in the park, making it a global hot spot. Biologists suspect there are another 100 slime mold species lurking in the park yet undiscovered, their microscopic mouths diligently munching away on bacteria.
Slime molds have an uncanny ability to mine bacteria from rotten logs, dung and decomposing soil. Bacteria are a dime a zillion in the forest, but are too small and scattered to be a useful food source to most animals — except slime molds that is.
“Bacteria is a wonderful food source, but it’s hard to pick up these organisms,” said Super. “Slime molds are going around wolfing down bacteria. It’s a great way to get the energy that is in bacteria into the food web.”
Slime mold’s crucial role in the food chain is similar to that of cattle. Humans could munch hay all day but would get little sustenance out of it. Cattle, on the hand, easily subsist on hay and convert it to a nutritional form then consumed by humans — providing a major stepping stone in the food chain.
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Occasionally, the slime molds get a hankering to reproduce. They throw off their microscopic guise and spring from dormancy into a multi-colored display.
“If you study it over the course of the day you can actually see it’s movement,” Super said. “We are not used to something that looks like fungus moving around.”
This confuses scientists when it comes to the most basic question for any species: plant or animal?
“They are thrown all manner of different places,” Super said. “It’s not a plant. It is not really related to fungus. It moves around but it is not really an animal, so no one knows what to do with it.”
But they do make a good pet if you can find the right one, Super said. Super knows of slime mold fans who have taken a piece of bark, soaked it overnight, sealed it in a Petri dish and put it on their desk and waited for the slime mold to fruit. The previously invisible conglomeration of nuclei sprout into a colorful display, like a miniature of the one Super found in his garage.
After they reproduce, they sink back into the bark. To see the slime mold again, simply reconstitute the bark and force it to fruit again. It’s the biologist’s version of a chia pet, or possibly a bonsai tree.
These fruiting, sporing slime molds have two cousins in the slime mold family that behave a little differently. They are quite a bit smaller,known as cellular slime molds.
These cellular molds are quite capable of foraging through life on their own. But the notion occasionally strikes them to form a small society — namely when it’s time to reproduce. They clump together — forming a unit the size of a grain of sand if they’re lucky — and divide up the chores. One set does the feeding, another does the moving about and another set does the reproducing. Scientists are puzzled over how the slime molds decide amongst themselves which ones are the lucky set that gets to reproduce, versus the ones relegated to more lowly chores.
“No one is quite sure what they get out of it,” Super said. “What dictates which ones get to be the spore producers? Is it altrusism? Are they actually secretly related, and they’ve gone their separate ways and are now coming back to help their brothers reproduce? No one has a particularly satisfying explanation.”
Scientists possibly did slime molds a disservice when they named the poor creatures. The two types of cellular slime molds are called myxomycetes and dictyostelids, and bigger fruiting kinds are called protostelids. With names like that, they could be destined for a life of obscurity.
But not if Super has anything to do with it. Super is the coordinator of a project to document and assess all the species of slime molds on earth. The five-year project is being funded by a National Science Foundation Planetary Biodiversity Grant.
“We are part of a global effort to really figure out what species are there and what is their distribution in the world,” Super said.
Slime molds could hold the key to medical cures (see related article.) But they could also prove a valuable measure of a healthy — or unhealthy — environment. Slime molds could occur in smaller numbers when pollution is present. Slime mold could also be a measure of biodiversity.
“We don’t know the details yet, but we hypothesize they could be used for doing tests of ecosystem health,” Super said.
Slime molds love the Smokies’ vast array of habitats, with a little something for all of them, even the pickiest of eaters.
“Some are more cosmopolitan, while some are specific to microhabitats, like on bat guano in caves,” Super said.
Since the Smokies is home to so many different species of plants and animals — likely more per acre than anywhere in North America —slime molds with a fetish for a particular brand of dung or decaying plant matter can find it in the Smokies. Cataloochee and Purchase Knob, both in the Haywood County section of the park, have proven particularly plentiful in slime molds.
The Smokies is already under the biodiversity microscope for its on-going All Taxa Biodiversity Inventory, a massive undertaking to document every living organism in the park. Scientists from across the globe are making pilgrimages to the park to help catalogue its organisms. The effort has netted more than 500 new species so far, and thousands not previously thought to dwell in the park.
To pull off the All Taxa Biodiversity Inventory — a project that will involve hundreds of scientists from around the world and likely span a quarter of a century — the Smokies and its non-profit partner Discover Life in America crafted a strategy to orchestrate the otherwise disparate teams of researchers and unite their findings into one record.
So when the National Science Foundation set aside money to study slime molds, the Smokies was appointed a lead role. The Smokies even had its own slime mold team already on deck as part of the All Taxa Biodiversity Inventory.
John Landolt, a slime mold expert and biology professor at Shepherd University in West Virginia, comes on regular expeditions to the Great Smoky Mountains National Park to collect slime mold species.
“The harder you look, the more you find,” Landolt said, who has turned up 10 new slime mold species so far. “They’re interesting critters in and of themselves.”
Super appealed to 30 other national parks — from Hawaii to Maine — to seek out slime molds in their territory. The parks represent every possible ecosystem the country has to offer — from deserts and volcanoes to bayous and beaches, Super said. Last spring, researchers, teachers and volunteers came here form a slime mold camp where Super taught them how to collect slime mold samples.
The other key to the National Science Foundation slime mold project is the University of Arkansas, where Dr. Steve Stephenson is the lucky recipient of all these slime molds samples being collected across the county.
