New groups of Archaea discovered in acidic hot springs in Yellowstone

Marsarchaeota
Marsarchaeota

An article published in the journal “Nature Microbiology” reports the discovery of a new group of archaea that was called Marsarchaeota. A team of microbiologists from Montana State University (MSU) discovered these microbes in Yellowstone National Park, USA, in hot springs where temperature and acidity are high and the main mineral is iron oxide. Their discovery could offer new information on their evolution and in general on the origin of life on Earth and on the importance of iron in the early stages of its history.

Archaea, or archaebacteria, are single-celled organisms lacking a nucleus. Knowledge about archaea is still limited, but in recent years advances in genetic analysis techniques expanded it enormously. The hot and acid springs of Yellowstone National Park are among the environments in which microorganisms of various types were searched for in extreme environments and in July 2016 an article published in the journal “Nature Communications” described the discovery of archaea.

The MSU researchers discovered archaea that in their opinion form a phylum hitherto unknown they called Marsarchaeota. The name derives from Mars and refers to the presence of iron oxides on the red planet and these archaea thrive in a habitat where a mineral of that type is abundant. Two different sub-groups living around the park’s springs were identified: one lives in waters above 50° Celsius (122° Fahrenheit), and the other lives in waters between 60° and 80° Celsius (between 140° and 176° Fahrenheit). The water is acidic and the microbe mats are red due to the iron oxide.

The image (courtesy Jay et al / Nature Microbiology. All Rights Reserved) shows a sample of the microorganisms present in Yellowstone National Park’s Echinus Geyser. The red arrow points to Marsarchaeota, whose size is slightly more than one thousandth of a millimeter.

The microorganisms present in what was compared to microbial versions of beaver dams produce iron oxide that creates terraces, which block the flow of water within the springs. When the water, which has a depth of only a couple of millimeters, flows over the terraces, oxygen is captured by the atmosphere and supplied to Marsarchaeota, which can use iron oxides in their metabolism.

A very interesting discovery is that the Marsarchaeota don’t oxidize iron but they reduce it and are aerobic so they can live in the presence of oxygen if it doesn’t reach too high levels. These are conditions that may exist normally in Yellowstone’s hot springs, where there’s an iron cycle in which different bacteria and archaea of different phyla produce iron oxide which is used by Marsarchaeota.

Archaea could be the most ancient complex life forms on Earth and Yellowstone’s habitat has similarities with those in which perhaps their primordial forms evolved. This means that their study can offer new information on the evolution of life on Earth. With their metabolism quite different from that of eukaryotic organisms they can also provide new ideas to develop biotechnologies.

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