After a decade of research, scientists studying geothermal features in Yellowstone National Park have found a new lineage of the ancient life form archaea. They believe the single-celled organism could unlock secrets of how early life began on Earth, and what life might look like on other planets.
“The discovery of archaeal lineages is critical to our understanding of the universal tree of life and evolutionary history of the Earth,” wrote the authors in their paper published in Nature Microbiology.
Named after the Red Planet, the two newly discovered subgroups of Marsarchaeota thrive in the hot waters, which are rich in iron oxide and are as acidic as grapefruit, throughout the park; one lives in water above 50°C (122°F), the other in water between 60 and 80°C (140-176°F).
Archaea are perhaps the oldest life forms on Earth and join the ranks of bacteria and eukaryotes – which contain humans and other complex species – to make up the three domains of life.
The Marsarchaeota live “fairly deep” within microbial mats – microscopic communities in aquatic environments – that get their deep-red coloring from high levels of iron oxide, the main component of rust. Here, Marsarchaeota are so abundant that they account for as much as half of all organisms in a single mat. Similar habitat types to these “mats” probably played an important role in the evolution of archaea, both on Earth and potentially beyond.
Microbial mats throughout Yellowstone act as “microbial beaver dams”. The iron oxide they produce blocks streams and forms terraces. Water just a few millimeters deep trickles over the terraces where oxygen is captured and supplied to Marsarchaeota. Unlike other microbes that produce iron oxide, the researchers think Marsarchaeota might be involved in reducing iron to a simpler form, which is important from an early Earth standpoint. According to the researchers, “iron cycling has been implicated as being extremely important in early Earth conditions."
Just like these mats, Mars’ distinctive red color also comes from the oxidization of iron on its surface.
"It's interesting that the habitat of these organisms contains (iron) minerals similar to those found on the surface of Mars," said Montana State University's Professor William Inskeep in a statement.
"Knowing about this new group of archaea provides additional pieces of the puzzle for understanding high-temperature biology. That could be important in industry and molecular biology."