Spatially Resolved Chemical Analysis of Geobacter sulfurreducens Cell Surface

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Geobacter sulfurreducens is known for efficient power generation and extracellular electron transfer (EET).
• The specific molecules responsible for EET in G. sulfurreducens remain unclear despite extensive research.
• Understanding these conductive pathways is crucial for bioelectronic applications.

Purpose of the Study:

• To identify and localize conductive compounds, particularly iron (Fe)-containing particles, on G. sulfurreducens.
• To investigate the role of these Fe-containing particles in bacterial extracellular electron transfer.
• To correlate findings with bacterial metabolic activity and potential for bioinorganic interface design.

Main Methods:

• Utilized energy-dispersive X-ray spectroscopy (EDX) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).
• Achieved near-atomic spatial resolution for chemical compound detection, identification, and localization.
• Analyzed Fe spatial distribution on G. sulfurreducens cell surfaces and within conductive filaments.

Main Results:

• Discovered small, uniformly sized (5.6 nm diameter) Fe-containing particles on the bacterium's surface, comparable to single protein size.
• Observed Fe atoms within G. sulfurreducens filaments, termed "bacterial molecular wires".
• Found that bacteria can adjust the spacing of Fe-containing bundles in filaments, facilitating efficient electron transfer.

Conclusions:

• The identified Fe-containing particles are likely key molecular conductors facilitating EET in G. sulfurreducens.
• Bacterial metabolic activity influences the arrangement of conductive Fe-containing structures.
• These findings provide insights for designing artificial biomolecular wires and bioinorganic interfaces.