Microbial interspecies electron transfer via electric currents through conductive minerals

Area of Science:

• Microbiology
• Geochemistry
• Biogeochemistry

Background:

• Interspecies electron transfer (IET) is crucial for microbial cooperation and community functions in anaerobic environments.
• Current IET mechanisms rely on chemical diffusion or direct cell contact.
• The role of natural conductive minerals in microbial electron transfer remains largely unexplored.

Purpose of the Study:

• To investigate the potential of conductive minerals facilitating IET.
• To explore novel mechanisms of microbial electron transfer beyond diffusion and direct contact.
• To understand the ecological implications of microbe-mineral electrical interactions.

Main Methods:

• Utilized electrically conductive magnetite nanoparticles to facilitate IET between Geobacter sulfurreducens and Thiobacillus denitrificans.
• Compared the efficiency of IET using conductive nanoparticles versus diffusive Fe ions.
• Assessed the impact of semiconductive and insulating iron-oxide nanoparticles on cooperative catabolism.

Main Results:

• Electrically conductive magnetite nanoparticles significantly accelerated IET, enabling efficient acetate oxidation coupled to nitrate reduction.
• Cooperative catabolism was observed with Fe ions, but at a slower rate (one order of magnitude).
• Semiconductive and insulating iron-oxide nanoparticles did not enhance cooperative catabolism, highlighting the importance of electrical conductivity.

Conclusions:

• Microbes can utilize conductive mineral particles as conduits for efficient interspecies electron transfer.
• This microbe-mineral electrical interaction offers ecological advantages by reducing energy costs for IET.
• Ubiquitous conductive minerals likely play a significant role in coupling biogeochemical reactions in natural ecosystems.