{"id":249923,"date":"2017-12-05T18:00:21","date_gmt":"2017-12-05T20:00:21","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=249923\/"},"modified":"2017-12-05T18:00:21","modified_gmt":"2017-12-05T20:00:21","slug":"bacteria-that-preserve-fossils","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/bacteria-that-preserve-fossils\/","title":{"rendered":"Bacteria that preserve fossils"},"content":{"rendered":"
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Os\u00e9s, G. L. et al \/ Scientific Reports<\/span><\/a> Two geochemical processes preserve delicate vertebrate structures: kerogenization…Os\u00e9s, G. L. et al \/ Scientific Reports<\/span><\/p><\/div>\n

The Araripe basin, at the boundary of the states of Cear\u00e1, Piau\u00ed and Pernambuco, is one of those rare places on the planet that holds a vast array of prehistoric animal fossils whose soft tissue is well preserved. Generally, these structures\u2014eyes, conjunctive tissue and fragments of heart fiber\u2014are the first to decompose so they rarely become fossilized. In those rare instances where they are preserved, they provide a basis for studies on the biology and evolution of species that have been extinct for millions of years. For some time, scientists have known that these structures are preserved as a result of specific geochemical processes that occur, such as the replacement of organic material by pyrite, a mineral composed essentially of iron and sulfur, or by kerogen, the insoluble part of organic matter that is retained in sedimentary rocks. In a May 2017 study published in the journal Scientific Reports<\/em>, researchers analyzed these processes microscopically and suggested that they might be affected by the respiration of decomposing bacteria.<\/p>\n

In the study, the team led by paleontologist M\u00edrian Pacheco of the Department of Biology at the Federal University of S\u00e3o Carlos (UFSCar), Sorocaba campus, and geologist Setembrino Petri of the Institute of Geosciences at the University of S\u00e3o Paulo (IGc-USP), examined fossil samples from a species of primitive fish called Dastilbe crandalli<\/em>, which lived in the area about 113 million years ago. The fossils, abundant in Araripe, were located in two types of limestone, sedimentary rock that is rich in calcium carbonate: one was gray and had more organic matter, and the other was beige and had fewer of these chemical compounds.<\/p>\n

The first samples were wrapped in a grayish fiber material. The beige-colored limestone samples in turn were an orange, honeycomb-like color, with a fuzzy covering of microscopic crystals.<\/p>\n

The researchers confirmed that the soft structures on the beige-colored fossils had been preserved through a pyritization process. \u201cThis means that the elements that these fossils were composed of were replaced by pyrite,\u201d explains Pacheco. Pacheco says that this is the first time a case of pyritization has been observed in a fossilized vertebrate. The few known registered cases are of insects and various invertebrates. At the same time, the soft tissue of the gray-colored limestone samples was fossilized through the formation of kerogen. In this process, organic carbon takes on a more stable form, which can persist for millions of years. While the pyritization process helped to preserve tendons, cellular nuclei and membranes and eye tissue, the kerogenization process preserved conjunctive tissue, tegument and muscle fiber.<\/p>\n

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Os\u00e9s, G. L. et al \/ Scientific Reports<\/span><\/a> …and pyritizationOs\u00e9s, G. L. et al \/ Scientific Reports<\/span><\/p><\/div>\n

In both cases, however, these geochemical processes were affected by the action of decomposing bacteria. Through the process of anaerobic respiration\u2014there is no oxygen involved\u2014the microorganisms assisted in replacing organic matter with pyrite or kerogen, depending on the type of limestone in which the fossils were preserved. As these processes got underway, the elements making up the organic structures of these animals were slowly destroyed and replaced by pyrite or kerogen. At the same time, they left marks on the rocks that encased them.<\/p>\n

Like in china<\/strong>
\nThis hypothesis is essentially based on electronic microscopy analysis. In examining pyritized fossils, researchers identified the residue of microorganism activity. \u201cWe found smooth and flexible structures, similar to a spider\u2019s web that are the result of the bacteria\u2019s metabolization of pyrite,\u201d says Pacheco. This would explain why each geochemical process would preserve the soft tissue in a particular way. Although both preserve these structures in their own way, the fossil fragments of soft tissue found in the beige-colored sediment, on a microscopic level, are even better preserved than those deposited in gray-colored limestone,\u201d explains geologist Gabriel Os\u00e9s, the study\u2019s first author and master\u2019s thesis advisor to Setembrino Petri during some of his research on the project.<\/p>\n

\u201cThe study is important because it broadens the area where these processes occurred to include other geological deposits, and it clarifies the geochemical conditions that led to the preservation of soft tissue in fossils in the Araripe basin,\u201d says paleontologist Marcello Guimar\u00e3es Sim\u00f5es, at the Institute of Biosciences at Sao Paulo State University (Unesp), Botucatu campus, who did not participate in the study. Sim\u00f5es says that prior to this point, people thought that these processes occurred in the soft tissue of fossils only in specific regions, like the Gaojiashan Formation in China, and during geological periods prior to the Cretaceous period, which stretched from 145 to 66 million years ago. \u201cNow we know that these geochemical processes can also be observed in fossils from more recent geological eras and possibly, in other geological deposits around the world.\u201d<\/p>\n

Project<\/strong>
\nApplications of Raman Spectroscopy in paleobiology and astrobiology (No. 12\/18936-0<\/a>); Grant Mechanism\u00a0<\/strong>Regular Research Grant; Principal Investigator<\/strong>\u00a0Setembrino Petri (USP); Investment<\/strong>\u00a0R$584,668.54.<\/p>\n

Scientific Article<\/em>
\nOS\u00c9S, G. L. et al<\/em>. Deciphering pyritization-kerogenization gradient for fish soft-tissue preservation<\/a>. Scientific Reports.<\/strong> Vol. 7. No. 1468, pp. 1-15. May 2017.<\/p>\n","protected":false},"excerpt":{"rendered":"The action of microorganisms may help preserve fragments of soft tissue","protected":false},"author":346,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[259,240,255],"coauthors":[662],"class_list":["post-249923","post","type-post","status-publish","format-standard","hentry","category-science","tag-chemistry","tag-geology","tag-paleontology"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/249923","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/346"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=249923"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/249923\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=249923"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=249923"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=249923"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=249923"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}