The Big Thaw

Permafrost contains multitudes of trapped microbes that have been locked up in a deep freeze; in some cases, for half a million years. As the Arctic warms and the permafrost thaws, viruses, bacteria, and fungi are released into the soil, the atmosphere, and the water. What threats, if any, might ancient microbes pose to human health? To help answer this question, Laboratory microbiologist Armand Dichosa and computer modeler Michael Brown teamed up with evolutionary wildlife biologist Devin Drown from the University of Alaska, Fairbanks. Here's how their idea works. 

A mammoth was killed by a microbe 50,000 years ago. Frozen in permafrost ever since, the microbe is a possible ancient human pathogen. Trapped within the earth's 8.8 million square miles of permafrost are unknown volumes of microbes with pathogenic potential.

Modern researchers collect samples from three kinds of sites found across the range: intact, partially thawed, or thawed permafrost. Through these sites' defining characteristics, inferences are made about how environmental factors control the presence, population, and distribution of different organisms. 

In a lab, all biological material is separated from the sampled soil and genetically sequenced using high-throughput techniques.

The genetic sequences are then compared to open-source databases, such as the National Center for Biotechnology Information, that contain the sequences of known pathogens. Genetic relatives of known pathogens are flagged, and an average is created to represent the candidate pathogen’s distribution across the permafrost’s range.

Different projected climate change scenarios are then linked to permafrost thaw and the subsequent release of potential pathogens. Using an aerosol dispersal model, a hydrologic dispersal model, and a model that looks at microbe uptake in plants, Dichosa and his team can begin to understand how climate change may release ancient pathogens, and what that may mean for mankind.

—Kyle Dickman