The occurrence of 2-methylhopanoids in modern bacteria and the geological record
| Autor: | B D A Naafs, Patricia Sánchez-Baracaldo, Fanny M. Monteiro, Giorgio Bianchini |
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| Rok vydání: | 2021 |
| Předmět: |
Biogeochemical cycle
Environmental change Ecology Fossils Marine habitats Geology Biology Geologic record Cyanobacteria cyanobacteria Biological Evolution Triterpenes Precambrian hopanoids Habitat Phanerozoic biomarker General Earth and Planetary Sciences Dominance (ecology) bacteria 2-methylhopanes Ecology Evolution Behavior and Systematics General Environmental Science |
| Zdroj: | Naafs, B D A, Bianchini, G, Monteiro, F M & Sanchez-Baracaldo, P 2022, ' The occurrence of 2-methylhopanoids in modern bacteria and the geological record ', Geobiology, vol. 20, no. 1, pp. 41-59 . https://doi.org/10.1111/gbi.12465 |
| ISSN: | 1472-4669 |
| DOI: | 10.1111/gbi.12465 |
| Popis: | The 2-methylhopanes (2-MeHops) are molecular fossils of 2-methylbacteriohopanepolyols (2-MeBHPs) and among the oldest biomarkers on Earth. However, these biomarkers’ specific source is currently unexplained, including whether they reflect an expansion of marine cyanobacteria. Here we study the occurrence of 2-MeBHPs and the genes involved in their synthesis in modern bacteria and explore the occurrence of 2-MeHops in the geological record. We find that the gene responsible for 2-MeBHP synthesis (hpnP) is widespread in cyano- and ⍺-proteobacteria, but absent or very limited in other classes/phyla of bacteria. This result is consistent with the dominance of 2-MeBHP in cyano- and ⍺-proteobacterial cultures. The review of their geological occurrence indicates that 2-MeHops are found from the Paleoproterozoic onwards, although some Precambrian samples might be biased by drilling contamination. During the Phanerozoic, high 2-MeHops relative abundances (index > 15 %) are associated with climatic and biogeochemical perturbations such as the Permo/Triassic boundary and the Oceanic Anoxic Events. We analysed the modern habitat of all hpnP-containing bacteria and find that the only one species coming from an undisputed open marine habitat is an ⍺-proteobacterium acting upon the marine nitrogen cycle. Although organisms can change their habitat in response to environmental stress and evolutionary pressure, we speculate that the high sedimentary 2-MeHops occurrence observed during the Phanerozoic reflect ⍺- proteobacteria expansion and marine N-cycle perturbations in response to climatic and environmental change. |
| Databáze: | OpenAIRE |
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