New research sheds light on how early life forms transitioned from a low-oxygen atmosphere to today’s oxygen-rich environment.
In a recent publication in the journal Nature Communications, scientists from Montana State University’s College of Agriculture present new insights into how ancient microorganisms evolved from a prehistoric environment with low oxygen levels to our current atmosphere. This study builds upon over twenty years of research conducted by MSU professor Bill Inskeep in Yellowstone National Park.
The article, titled “Respiratory Processes of Early-evolved Hyperthermophiles in Sulfidic and Low-oxygen Geothermal Microbial Communities,” was released on January 2. Authors Inskeep, a faculty member in the Department of Land Resources and Environmental Sciences, and Mensur Dlakic, an associate professor in the Department of Microbiology and Cell Biology, studied heat-loving organisms in two specific thermal features of Yellowstone, Conch Spring and Octopus Spring, both found in the Lower Geyser Basin of the park.
Inskeep and Dlakic chose these sites because their geochemical profiles share many similarities, differentiation occurring mainly in the levels of sulfide and oxygen, with Conch Spring having higher concentrations of both compared to Octopus Spring. This allowed the researchers to analyze two distinct thermal environments that exhibit low and high oxygen levels.
Both springs, which maintain temperatures around 190 degrees Fahrenheit, hosted three types of thermophilic microbes—organisms that flourish in hot conditions. The research suggests that these microbes’ behaviors in their respective environments provide valuable insights into life’s evolution before and during the Great Oxidation Event, a significant time around 2.4 billion years ago when Earth’s atmosphere shifted from being nearly devoid of oxygen to containing almost 20% oxygen as it does today.
“As oxygen levels began to rise, it’s likely these thermophiles played a crucial role in the emergence of microbial life,” said Inskeep, who has been conducting research in Yellowstone since 1999. “With more oxygen available at Octopus, there’s a higher presence of aerobic organisms there. Each environment supports different types of life.”
The microorganisms analyzed by Inskeep and Dlakic are housed within “streamers,” which thrive in the fast-moving water currents. These streamers resemble small kelp plants, anchoring themselves to rocks and other surfaces while growing filaments that sway in the water.
Despite their similar appearance, the streamers from Conch and Octopus springs displayed significantly varied microbial communities. While three species of microbes were shared between both locations, the higher-oxygen environment of Octopus Spring showcased a much greater diversity, providing insights into how these organisms adapted to a world with more oxygen, according to the researchers.
The authors examined the respiratory genes in microbes from Conch and Octopus Springs. They found that genes suited for extremely low oxygen were “highly expressed”—indicating heightened activity—in Conch Spring, whereas organisms in Octopus Spring largely expressed genes that are adapted for increased oxygen levels, likely becoming essential as oxygen became more prevalent during the Great Oxidation Event.
Throughout his thirty years at MSU, Inskeep has gathered extensive data from Yellowstone but believes there is still much to uncover and many questions to explore. In 2020, he and Dlakic received funding from the National Science Foundation’s Opportunities for Promoting Understanding through Synthesis program to further investigate Yellowstone’s thermophiles, and their ongoing collaboration continues to reveal previously unknown details about the origins of life on Earth.
Inskeep emphasized that the location of MSU within the Greater Yellowstone Ecosystem is perfect for this type of research.
“Attempting to recreate this kind of experiment in a lab would be extremely challenging; envision trying to create hot-water streams with precise levels of oxygen and sulfide,” he stated. “Studying these unique environments allows us to observe organisms in the exact geochemical setting they need to thrive.”
While the activities of these hot spring-dwelling organisms might appear disconnected from human life, they provide crucial understanding of how human life developed and how various organisms adapt to their environments to survive, remarked Dlakic.
“It might seem odd to learn about complex life by studying simple organisms, but that’s where it all begins,” he noted. “We must look back to understand how we arrived at our current state.”
