Researchers identify microbes in centuries-old snail guts

Rocky Mountain snails live at high elevations in sites ranging from Canada to southern New Mexico. Credit: Brigitte Chalifour

On a rainy day in July 1920, a Colorado scientist named Junius Henderson was hiking around the Dakota Hogback, a sandstone ridge north of Boulder. There he spotted a group of Rocky Mountain snails (Oreohelix strigosa) oozing on the floor. Henderson collected the molluscs and brought them back to his laboratory at what is now called the University of Colorado Museum of Natural Historycarefully preserving his finds.

Now, a century later, a team of ecologists from the CU Museum has returned to these snails, gaining startling insights into something Henderson couldn’t have predicted at the time: the diverse communities of bacteria and bacteria. other microbes, known collectively as the microbiome. , which flourished in the entrails of molluscs.

For the first time ever, researchers have used modern DNA screening tools to identify microbes that once lived in the guts of animals that had been dead for a century. Bridget Chalifour, who led the study, said the results show how valuable museum collections can be – microbiomes could offer an unexpected window into how animals interacted with their environment from the time of the prohibition, or even further.

“We’ve learned that samples from 50 or 100 years ago have as much viability in answering modern ecological questions as samples collected just two years ago,” said Chalifour, who recently earned his doctorate in ecology. and evolutionary biology from CU Boulder.

She and her colleagues published their results in the magazine Microbiota.

The findings come as scientists realize how important gut microbiomes are to many animals and even humans. Recent research from CU Boulder, for example, has shown that a healthy population of gut bacteria can help people fight stress or even sleep better.

The new approach doesn’t have to stop at snails: Scientists could use a similar method to scan the microbiomes of a range of other animals that museums often store in ethanol, including many spiders, frogs and snakes.

“This work opens the door to limitless possibilities,” said study co-author Jingchun Li, curator of invertebrates at the museum and assistant professor of ecology and evolutionary biology. “This means that millions of museum specimens accumulated over centuries around the world can be used for microbiome research.”

keep an eye out

You may never have seen a Rocky Mountain snail, even though you’ve lived and hiked in Colorado for years. These animals, which are about the size of your thumbnail, munch on leaves and other plant matter at sites ranging from Canada to southern New Mexico.

But they tend to only come out when wet.

“When it rains, they’re usually grazing on rocks or trees in places like Eldorado Canyon in Boulder,” Chalifour said.

Over the years, Boulder researchers have collected about 1,000 of these snails, storing them, like Henderson’s early finds, in ethanol.

“Museum specimens and artifacts are the next best thing to a time machine,” Li said. has shaped mountain plant communities over time. We can detect which organisms survived mass extinction events.

Li and Chalifour, along with a former collections manager at CU Boulder named Leanne Elder, decided to take a special look at snail guts.

Populations lost

The team assembled a collection of 55 Rocky Mountain snails collected between 1920 and 2018 from an area stretching from Boulder in the east to Telluride in the southwest. They included three snails that Henderson, whose name now adorns the main museum building on campus, had found. The researchers then gutted the molluscs. The microorganisms in their intestines had also been dead for decades, but the team was able to sequence what was left of their DNA.

The bold approach paid off. When they died decades ago, the molluscs were full of life. Researchers have identified evidence of more than 7,000 organisms, mostly bacteria, hidden inside each snail. Nor did ethanol seem to degrade their DNA. The team found just as diverse microbiomes in Henderson’s century-old samples as they did in the snails that Chalifour had collected herself and never stored in a jar.

“It’s exciting for me because I’ve now deposited a lot of samples in the museum,” Chalifour said. “I like to think about what people might do with my snails in 15 years.”

She noted that the microbiomes of snail specimens have changed quite a bit over the century for reasons that are unclear. Henderson’s molluscs, for example, harbored many bacteria belonging to the genera Bradyrhizobium, Alicycliphilus and Cloacibacterium. The snails collected in 2018, meanwhile, were partial to Flavobacterium and the families Chitinophagaceae and Cerasicoccaceae. However, where the animals lived mattered much more, accounting for about 20% of the microbial variation among snails.

These microorganisms, Chalifour said, likely helped snails earn a living in the Rocky Mountains: Many of the bacteria the team discovered belonged to groups often able to break down complex organic molecules, like cellulose in leaves. that snails eat.

Today, droughts and wildfires can push these wet weather animals out of their former habitats, Chalifour added. She spent days searching for snails in Boulder County where Henderson collected her original specimens. She couldn’t find any.

“A lot of the populations that we have in our collections are no longer there,” Chalifour said.

Republished with kind permission from the University of Colorado at Boulder.

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