A Bundled Antiparallel Cytochrome Nanowire Structure Suggests Roles in Cell-Cell Electron Transfer and Biofilm...

Area of Science:

• Microbiology
• Biophysics
• Electrochemistry

Background:

• Microbes utilize extracellular electron transfer (EET) for respiration using minerals or electrodes.
• Long-range EET relies on micrometer-long microbial nanowires, primarily studied in *Geobacter sulfurreducens*.
• The structure and distribution of these conductive protein filaments remain largely unknown.

Purpose of the Study:

• To determine the atomic structure of a novel cytochrome nanowire from *Desulfuromonas soudanensis*.
• To investigate the higher-order assembly and potential commonality of microbial nanowires.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to resolve the atomic structure.
• Comparative analysis with related species like *Geobacter metallireducens*.

Main Results:

• A unique cytochrome nanowire from *D. soudanensis* was structurally characterized.
• These nanowires assemble into highly ordered bundles of antiparallel filaments.
• Similar bundle structures were found in *G. metallireducens*, suggesting a conserved quaternary structure.

Conclusions:

• Cytochrome nanowires from diverse microbes can form specialized bundles, potentially aiding conductive biofilm formation.
• This quaternary structure represents a novel microbial strategy for electron exchange.
• Findings advance understanding of EET mechanisms and could inform biofilm engineering for electrochemical applications.