Where There's Soup, There's Life

Early Earth was a hot environment, and it's possible that some of the life that we see today in hot springs in places like Yellowstone National Park and at deep-sea hydrothermal springs along mid-ocean ridges may share some common metabolic features with their early Earth ancestors. So determining what life exists in hot springs today is one of the first steps to define what early life on a hot planet may have been like.

These thermophiles "living in hot springs are microscopic, and are hard to identify just by looking at them under the microscope," explained Reysenbach from Portland State University. She uses biogeochemical, molecular, and microbiological approaches to study the ecology of thermophiles.

"Essentially there are two ways to identify these microbes; either by trying to grow them, or by using molecular techniques that identify an evolutionarily conserved gene, a sort of fingerprint, of the organism. Using a combination of these approaches, we have been able to grow a very prevalent and important member of hydrothermal ecosystems.

"This group of organisms are chemolithoautotrophs, they use inorganic energy and carbon sources, and are the deepest lineage within the universal tree of life," she explained. "Although the trunk and base of the tree of life are much debated, these few pieces of evidence suggest that this group of organisms may be a good proxy for studying early Earth life. Understanding how these organisms fossilize, what remaining biological signatures they may leave behind, how they precipitate minerals etc. will perhaps help us interpret the rock record here on Earth and other planets more effectively."

The important member of this group is the Aquificales, a deeply-rooted lineage that is common in both terrestrial and deep-sea hydrothermal systems. Reysenbach looks forward to receiving the genome of one of the isolates, "Persephonella marina," which will be available in a few months.

"I think it will definitely show what type(s) of carbon fixation pathways this organism has, how it gets some of it's essential elements, N, C, P, etc.," she said. "What I am also very interested in is how different or similar it is to its relative Aquifex. When the genome sequence of Aquifex was released, it rocked the boat a little, since it showed that this organism is a VERY modern organism...and not what some thought would be typical of a 'primitive' -ancestral organism."

Reysenbach will present her research "Gourmet Geochemical “Primordial Soups” at Hydrothermal Vents Support Novel Thermophilic Chemolithotrophs: Implications for the Evolution of Life on Early Earth" on Wednesday, June 27, at the Earth Systems Processes conference in Edinburgh, Scotland. The Geological Society of America and the Geological Society of London will co-convene the June 24-28 meeting.