Soil Microbes Surviving 60-Year-Old Fire Reveal Negative Impact of Human Activities to the Environment

Microbes are important in maintaining healthy, fertile soil. By helping plants grow and decomposing organic matter, they play a vital role in the overall health of ecosystems. However, human activities can cause long-term damage to the environment.

(Photo: Wikimedia Commons/ Mredden)

Underground Coal Fire

A century ago, Centralia, Pennsylvania, was a busy mining center, with coal from local mines fueling its homes and economy. After mining began in the 1850s, it became home to a rich deposit of anthracite coal. Today, Centralia's streets are abandoned due to a mine fire that has been burning for several decades.

It is unclear how the tragedy began, but some theories suggest that it all started when an abandoned mine pit was converted into a garbage dump. Due to the problem with unwanted odors and rats, the city proposed in May 1962 to clean up the local landfill in time for the town's Memorial Day festivities.

The Centralia Council proposed setting it on fire, which sparked a much larger mine fire beneath the town. Soon, the fire raged in a coal seam beneath the town, making it the site of an underground coal mine fire that had been burning since 1962.

Understanding Survival of Dormant Microbes

Experts from Michigan State University provided answers on how human actions disrupt the environment. They analyzed soil microbes near a mine fire that had been burning for over 60 years. The result of their study is discussed in the paper "Arrive and Wait: Inactive bacterial taxa contribute to perceived soil microbiome resilience after a multidecadal press disturbance."

According to MSU's Department of Microbiology, Genetics, and Immunology adjunct associate professor Ashley Shade, soil has the most diverse microbiome known. Tens of thousands of different bacterial species are present in every gram of soil, which means that it is even more diverse than the human gut.

Shade has been studying soil microbial communities in Centralia, Pennsylvania, in collaboration with Samuel Barnett for seven years. In this study, the research team investigated the way bacterial communities respond and potentially recover from intense environmental change. This is particularly important in understanding the impact of another disturbance: climate change.

The scientists conducted annual sampling between 2015 and 2021. They chose sampling sites at various points along the fire's path and examined the soil before, during, and after heating. They also sampled from nearby areas that were completely undisturbed by the fire.

After soil sampling, the team extracted the genetic materials from the bacteria, sequencing the DNA to determine the type of bacteria present. Then, they compared the ratio of RNA to DNA to determine the biologically active bacteria and dormant ones. Dormancy refers to the state of activity assumed by many life forms at some point. It is a vital strategy that helps organisms withstand stress in their environment.

Centralia mine fire is an example of a press disturbance or a long-term, continuous disruption caused by human activities. Shade and her team hope to spur additional studies in developing strategies for restoring microbiomes in ecosystems affected by climate change and other press disturbances.