Embryo fossilization is a biological process mediated by microbial biofilms

Area of Science:

• Paleontology
• Microbiology
• Geochemistry

Background:

• Fossilized embryos with exceptional cellular preservation date to the Late Neoproterozoic and Cambrian periods, coinciding with the emergence of animal body fossils.
• Microbial processes are hypothesized to drive the preservation and mineralization of organic tissues, but experimental evidence for microbial roles in embryo preservation is lacking.

Purpose of the Study:

• To experimentally demonstrate the role of microbial biofilms in the preservation and mineralization of marine embryos.
• To elucidate the distinct steps involved in bacterial-mediated fossilization of soft tissues.

Main Methods:

• Utilizing cleavage-stage marine embryos as an experimental model for decay.
• Observing rapid bacterial biofilm assembly on dead embryos and analyzing cellular replacement using microscopy.
• Identifying bacterial taxa involved in decay via 16S rDNA sequencing.
• Investigating preservation under varying taphonomic conditions.

Main Results:

• Bacterial biofilms rapidly formed in dead embryos, creating pseudomorphs that precisely replicated cellular organization and structure.
• Embryo preservation occurred in three stages: autolysis blockage, biofilm formation/replacement, and bacterially catalyzed mineralization.
• Decay processes were consistent across different conditions, but bacterial population composition varied.
• Experimental taphonomy yielded preservation states mirroring those found in fossil embryos.

Conclusions:

• Bacterial biofilms play a crucial role in the fossilization of soft tissues through replacement and mineralization.
• This study provides an experimental foundation for understanding fossilization as a biological process mediated by microbial activity.
• Future research can involve creating biofilms from defined microbial species to model specific fossilization scenarios.