On Mount Everest, humans are leaving a frozen microbe legacy

On Mount Everest, humans are leaving a frozen microbe legacy ...

Baker Perry collects soil samples at a camp on the South Col, where hundreds of adventurers pitch their final campsite every year before trying to reach the world's tallest peak from the south.

The barren, wind-swept valley between Mount Everest and its neighboring summit, Lhotse, in the Himalayas, is still without snow. Thousands of thrill-seekers gather at the South Col to take on the world's highest peak from its southeast flank.

Researchers at the University of Colorado Boulder claim that these adventurers are inadvertently leaving behind a frozen footprint of resilient microbes. These microbes may survive severe weather at high altitudes and remain dormant in the soil for decades, or even decades.

The findings were published last month in Arctic, Antarctic, and Alpine Research, an online journal published by the Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder.

Even at that elevation, the microbiome of Everest contains a human signature, according to Steve Schmidt, a senior author of the study and professor of ecology and evolutionary biology.

Scientists have been unable to detect human-associated microbes in human samples taken above 26,000 feet for the first time, enabling researchers to examine soil from a high elevation on Mount Everest.

The researchers were unsurprised to discover microorganisms left by humans. Microbes are everywhere, even in the air, and can easily blow around and land a few miles away from nearby camps or trails.

"That's the sort of thing that might happen if somebody even blows their nose or coughs," said Schmidt.

Several microbes that have evolved to thrive in warm and wet environments such as our noses and mouths were flexible enough to survive in such extreme conditions.

Schmidt and lead author Nicholas Dragone, both graduate students at CU Boulder's Ecology and Evolutionary Biology, have studied the cryobiosphere: Earth's cold regions and the limits to life in them. They have sampled soils everywhere from Antarctica and the Andes to the Himalayas and the high Arctic. Typically, human-associated microbes don't show up in these places like they did in recent Everest analyses.

Schmidt's research over the years has connected him with researchers who were visiting Everest's South Col in May of 2019 to establish the planet's highest weather station, established by the National Geographic and Rolex Perpetual Planet Everest Expedition.

While you're there, he asked his colleagues. Would you mind taking some soil samples?

Baker Perry, an Appalachian State University professor of geography and a National Geographic Explorer, set out as far away from the South Col camp as possible to collect soil samples to send back to Schmidt.

Dragone and Solon then examined the soil in several laboratories at CU Boulder. Using next-generation gene sequencing technology and more traditional culturing techniques, they were able to identify the DNA of most living or dead microbes in the soils. They then performed extensive bioinformatics analyses of the DNA sequences to determine the diversity of organisms rather than their abundances.

The most abundant organism they found using both old and new techniques was a fungus from the genus Naganishia that can withstand extreme temperatures and UV radiation.

However, the researchers discovered microbial DNA for some organisms closely related to humans, including Staphylococcus, a common skin and nose bacteria, and Streptococcus, a dominant genus in the human mouth.

Microbes are often killed by ultraviolet light, cold temperatures, and limited water availability. Most organisms—like the microbes carried up great heights by humans—death or decompose, but Mount Everest is a Hotel California: "You may check out anytime you like," says the author.

Everest's tiny impact on the environment is unlikely to be significant, although this study does indicate that life may be possible far beyond Earth, if one day humans step foot on Mars or beyond.

"We may discover life on other planets or cold moons," said Schmidt. "We'll have to be careful not to disturb them with our own."

Nicholas B. Dragone, L. Baker Perry, Anton J. Solon, Tracie A. Seimon, and Steven K. Schmidt, "Genetic analysis of the frozen microbiome at 7900 m a.s.l. on the South Col of Sagarmatha (Mount Everest)" DOI: 10.1080/15230430.2023.2164999

The National Geographic and Rolex Perpetual Planet Everest Expedition, the Department of Ecology and Evolutionary Biology, and the University of Colorado Boulder Libraries provided funding for the project.

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