Science : La fossilisation

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Cette news n'est pas une grande avancée dans le domaine médicale ou quoi que ce soit d'équialent.
Non, je la trouve juste très étonnante, car je ne l'aurai jamais "intuiter".

L'origine de certains fossiles extrémement bien conservée est l'action des bactéries en trois étapes :

1) Blocage de l'autolyse (destruction des cellules) en modifiant les conditions anaérobiques

2) Calque/protection du corps par la production de biofilm (substance secreté par les bactéries, autres rôles : adhésion des bactéries ou résistance aux antibiotiques)

3) Catalysation de la minéralisation


Après, pourquoi est-ce que la nature a mis au point un système aussi ingénieux, je n'en sais vraiment rien.


Quel est le rôle, l'utilité, la finalité de ces fossiles ?

Dur de croire que ce délicat mécanisme soit juste le fruit du "hasard".


Citation:
Proc Natl Acad Sci U S A. 2008 Dec 1;


Embryo fossilization is a biological process mediated by microbial biofilms.

Raff EC, Schollaert KL, Nelson DE, Donoghue PC, Thomas CW, Turner FR, Stein BD, Dong X, Bengtson S, Huldtgren T, Stampanoni M, Chongyu Y, Raff RA.

Department of Biology and Indiana Molecular Biology Institute, Indiana University, Bloomington, IN 47405;

Fossilized embryos with extraordinary cellular preservation appear in the Late Neoproterozoic and Cambrian, coincident with the appearance of animal body fossils. It has been hypothesized that microbial processes are responsible for preservation and mineralization of organic tissues. However, the actions of microbes in preservation of embryos have not been demonstrated experimentally. Here, we show that bacterial biofilms assemble rapidly in dead marine embryos and form remarkable pseudomorphs in which the bacterial biofilm replaces and exquisitely models details of cellular organization and structure. The experimental model was the decay of cleavage stage embryos similar in size and morphology to fossil embryos. The data show that embryo preservation takes place in 3 distinct steps: (i) blockage of autolysis by reducing or anaerobic conditions, (ii) rapid formation of microbial biofilms that consume the embryo but form a replica that retains cell organization and morphology, and (iii) bacterially catalyzed mineralization. Major bacterial taxa in embryo decay biofilms were identified by using 16S rDNA sequencing. Decay processes were similar in different taphonomic conditions, but the composition of bacterial populations depended on specific conditions. Experimental taphonomy generates preservation states similar to those in fossil embryos. The data show how fossilization of soft tissues in sediments can be mediated by bacterial replacement and mineralization, providing a foundation for experimentally creating biofilms from defined microbial species to model fossilization as a biological process.

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