Elongated Riboflavin-Producing Shewanella oneidensis in a Hybrid Biofilm Boosts Extracellular Electron Transfer

Area of Science:

• Microbiology
• Synthetic Biology
• Materials Science

Background:

• Shewanella oneidensis performs extracellular electron transfer (EET), but efficiency is limited by low flavin levels, poor biofilm formation, and weak conductivity.
• Riboflavin (RF) was identified as crucial for EET in vitro.

Purpose of the Study:

• To enhance EET efficiency in Shewanella oneidensis through genetic engineering and materials science strategies.
• To improve biofilm characteristics and conductivity for increased microbial fuel cell performance.

Main Methods:

• Overexpression of riboflavin (RF) synthesis pathway and the cell division inhibitor sulA in S. oneidensis.
• Molecular dynamics simulations to understand RF-MtrC interaction.
• Development of a hybrid biofilm using RF, multiwalled carbon nanotubes (MWCNTs), and graphene oxide (GO).

Main Results:

• RF synthesis increased significantly, and RF was found to bind strongly to the outer membrane cytochrome MtrC.
• SulA overexpression enhanced biofilm thickness (155%) and biomass (77%).
• The hybrid biofilm achieved a 77.83-fold increase in power output (3736 mW m⁻²) and reduced charge-transfer resistance.

Conclusions:

• Combining synthetic biology (RF and sulA overexpression) with materials science (hybrid biofilm) significantly boosts EET in S. oneidensis.
• This approach offers a new paradigm for enhancing electrogenic bacteria performance for applications like microbial fuel cells.