2.72 billion years ago, in very salty volcanic lakes, microorganisms were able to metabolize arsenic, according to the work of researchers from the Institut de physique du globe of Paris (CNRS/IPGP/Univ. Paris Diderot), from the SOLEIL Synchrotron and from the Laboratoire Bioénergétique et ingénierie des protéines (CNRS/AMU), in collaboration with the Connecticut University (USA), which was published on the Nature Geoscience website on October 26 2014.
Scientists discovered “globules” of organic matter that contained pure arsenic (not mixed with other metals) by analyzing the chemical composition of Australian fossil stromatolites (1). These globules could be bacterial cells, that would have circumvented the arsenic toxicity, and used its oxidizing and reductive properties to produce energy. This is the first proof of the existence of such metabolism (2) in primitive living organisms. As a matter of fact, the conditions they lived in must have been similar to the primitive surface of Mars, a volcanic and sulfate-rich environment. This discovery has implications in the search for past life on other planets.
- cauliflower-like limestone clusters formed by the activity of microorganisms, for which the oldest samples are dated at circa 3.5 billion years
- found today in very salty lakes of the Andes or California
Caption: Tumbiana stromatolites, bulb-shaped lime concretions formed by the activity of microorganisms (highlighted by the calcium mapping, a) contain high concentrations of Arsenic (As) (b). Arsenic is present in organic matter globules (c, in red), which could be fossil bacterial cells.
Credits: Pascal Philippot