New Archaeal Lineage Discovered at Yellowstone

Archaea constitute a domain of single-celled microorganisms. These microbes (archaea; singular archaeon) are prokaryotes, meaning they have no cell nucleus.

Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this classification is outdated. Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukarya. The Archaea are further divided into multiple recognized phyla. Classification is difficult because the majority have not been isolated in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment.

They flourish in a bewildering variety of habitats, from the familiar- lands and oceans- into the inhospitable and bizarre. The Archaea are among the principal domains of cellular life, and are perhaps the most ancient form of existence: putative fossils of archaean cells in stromatolites are dated to nearly 3.5 billion decades back.

Like bacteria, these microorganisms are prokaryotic which means they don’t have any cell nucleus or some other organelles in their cells. They play big roles in modern-day biogeochemical cycles, and therefore are central to debates concerning the origin of eukaryotic cells.  But, knowing history and their origins is hard due to the time spans.

The Yellowstone National Park provides an unprecedented opportunity for studying these microorganisms that may represent analogues of early Earth thanks to its geochemically diverse thermal environments. Now, researchers have unearthed a new lineage of these microbes at the famously hot and acidic spring waters of Yellowstone National Park.

“The discovery of archaeal lineages is critical to our understanding of the universal tree of life and evolutionary history of the Earth,” said Montana State University’s Professor William Inskeep and co-authors. “Geochemically diverse thermal environments in Yellowstone National Park provide unprecedented opportunities for studying Archaea in habitats that may represent analogues of early Earth.”

The research team found two subgroups of Marsarchaeota- one of which lives in water over 122 degrees and the other that resides in water between 140 and 176 levels.

Professor Inskeep and team have named this new lineage the Marsarchaeota after Mars- because of their ability to thrive in habitats containing iron oxides. Both reside in water with roughly precisely the exact same acidity as grapefruit juice.  The archaea demand low levels of oxygen and don’t create iron but likely reduce the chemical into a simpler form.

“It’s interesting that the habitat of these organisms contains (iron) minerals similar to those found on the surface of Mars,” Professor Inskeep said. “Microbes produce iron oxide, but the Marsarchaeota do not. They might be involved in reducing iron into a simpler form, which is important from an early Earth standpoint. Iron cycling has been implicated as being extremely important in early Earth conditions.”

“The Marsarchaeota live fairly deep in microbial mats, but they still require low levels of oxygen,” he added. “The subgroups are so abundant that, together, they can account for as much as half of the organisms living within a single microbial mat.”