Periplasmic FeS Electron Conduits: Tuning Electrocoupling and Respiratory Dehalogenation in a Synthetic Consortium

Area of Science:

• Microbiology
• Biochemistry
• Environmental Science

Background:

• Electron transfer is a key limitation in anaerobic biotransformation of electron acceptor-type substrates (EATS).
• Organohalogens, such as hexabromocyclododecane (HBCD), pose environmental challenges due to slow degradation.
• Efficient electron delivery is crucial for microbial metabolism and bioremediation.

Purpose of the Study:

• To develop a novel strategy for enhancing electron delivery in bacterial cells for improved anaerobic biotransformation.
• To investigate the role of cysteine desulfhydrase (CSD)-associated periplasmic iron sulfide (FeS) biomineralization in facilitating electron transfer.
• To assess the effectiveness of this strategy in the debromination of HBCD within a synthetic coculture.

Main Methods:

• Development of a CSD-associated periplasmic FeS biomineralization strategy in a defined synthetic bacterial consortium.
• Utilizing hexabromocyclododecane (HBCD) as a model organohalogen for debromination studies.
• Employing electrochemical analyses, inhibitor profiling, and structure prediction to elucidate electron transfer mechanisms.

Main Results:

• Rapid formation of periplasmic FeS conduits within ~3 hours, enhancing electron transfer and capacitive storage.
• Cocultures demonstrated significantly improved electron transfer, electron-accepting capacity, and transport activity compared to monocultures.
• Evidence of dihaloelimination-dominated debromination of HBCD, with FeS conduits playing a crucial role.

Conclusions:

• Periplasmic FeS conduits, facilitated by CSD, offer an effective interfacial strategy to modulate electron flux in bacterial cocultures.
• This approach enhances the anaerobic biotransformation of organohalogens and other EATS by overcoming electron delivery bottlenecks.
• The findings highlight a transferable route for bioremediation of emerging environmental contaminants.