Preservation of Archaeal Surface Layer Structure During Mineralization

Area of Science:

• Microbiology
• Biomineralization
• Geochemistry

Background:

• Proteinaceous surface layers (S-layers) are common in prokaryotes, providing structural stability and influencing metal interactions.
• Previous studies noted S-layer-associated mineral formation but lacked mechanistic understanding.

Purpose of the Study:

• To elucidate the passive mechanisms of iron phosphate nucleation and growth within S-layers.
• To investigate the potential of S-layers as biosignatures in the fossil record.

Main Methods:

• Incubation of Sulfolobus acidocaldarius (a hyperthermophilic archaeon) and cell-free S-layer "ghosts" in iron-rich medium.
• Observation of passive iron phosphate nucleation and growth within the S-layer structure.
• Analysis of S-layer preservation during mineralization.

Main Results:

• A five-step passive process of iron phosphate nucleation and growth within S-layers was described.
• Mineralization occurred independently of metabolic activity, both on intact cells and S-layer ghosts.
• S-layer structures were well-preserved even after extensive encrustation, indicating potential for fossilization.

Conclusions:

• S-layers facilitate passive biomineralization of iron phosphates.
• The preserved S-layer structure offers potential biosignatures for ancient microbial life.
• This process is relevant to understanding mineral formation in metal-rich environments.