AsianScientist (Sep. 12, 2017) – In a study published in the journal Organic Geochemistry, researchers in Japan and China have identified new molecular fossils of archaea with a method of analysis commonly used in forensic science.
There are three domains of life on Earth: Archaea, Bacteria and Eukaryota. To date, the distribution of Archaea remains unclear, especially for geologic periods dating back more than two million years. This is because except for halophilic, methanogenic and methanotrophic archaea, molecular fossils of archaea are rarely found.
Studies of the molecular clock suggest that Archaea appeared around 3.8 billion years ago, while the results of more direct geological evidence from molecular fossils of archaea indicate that they appeared 0.2 billion years ago (with the exception of two records of 0.25 and approximately 2.7 billion years). The low biomass of archaea in earlier geologic periods or the decomposition of molecular fossils could account for the difference in the molecular and geological timelines.
In this study, a team led by Dr. Ryosuke Saito and Professor Kunio Kaiho of Tohoku University took sedimentary rock samples from southern China and analyzed the organic molecules in them using gas chromatography-mass spectrometry (GC-MS).
GC-MS is a conventional instrument found widely in organic geochemistry laboratories and has been regarded as a ‘gold standard’ for forensic substance identification. It is used in drug detection, fire investigation, environmental analysis and even the study of extraterrestrial samples. However, this is the first study to use GC-MS to detect and characterize molecular fossils.
The researchers detected a class of molecules known as biphytanes that are well known biomarkers for the presence of archaea in geological samples. They observed mono-, bi- or tricyclic biphytanes within uppermost Permian and Lower Triassic sedimentary rocks.
Saito’s team is now studying the archaeal distribution on Earth from more than two million years ago. They believe that by analyzing the fossils using the GC-MS method, it will be easier to find archaea in sedimentary rocks.
The article can be found at: Saito et al. (2017) Tentative Identification of Diagenetic Products of Cyclic Biphytanes in Sedimentary Rocks from the Uppermost Permian and Lower Triassic.
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Source: Tohoku University; Photo: Kunio Kaiho.
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