Experimental maturation of Archaea encrusted by Fe-phosphates

Area of Science:

• Astrobiology
• Geochemistry
• Microbiology

Background:

• Burial processes typically degrade biological signals.
• Mineral encrustations are often assumed to protect microorganisms from degradation.

Purpose of the Study:

• To investigate the effect of iron phosphate encrustation on microbial organic matter preservation under simulated burial conditions.
• To understand the molecular and mineralogical evolution of microbial-mineral assemblages.

Main Methods:

• Experimentally encrusting Sulfolobus acidocaldarius with amorphous iron phosphates.
• Subjecting samples to constrained temperatures (150°C) and pressure for 1-5 days.
• Analyzing samples using X-ray diffraction, electron microscopy, and X-ray absorption spectroscopy.

Main Results:

• Iron phosphates enhanced the chemical degradation of microbial organic matter.
• Crystalline lipscombite formed in the presence of S. acidocaldarius cells, trapping organic matter.
• Lipscombite texture was controlled by the initial organic matter to mineral ratio.

Conclusions:

• Mineral-microbe interactions during fossilization are complex and influence preservation.
• The assumption of enhanced preservation by mineral coatings may not always hold true.
• Interplay between minerals and organic matter is crucial for interpreting the fossil record.