Extracellular Electron Transfer by Shewanella oneidensis Controls Palladium Nanoparticle Phenotype.

Area of Science:

• Microbiology
• Materials Science
• Biotechnology

Background:

• Biological production of inorganic materials is limited by poorly understood genetic and metabolic links to material properties.
• Electroactive bacteria, like Shewanella oneidensis, are promising for material synthesis due to their physiology linked to inorganic transformations.
• While Shewanella oneidensis can produce metal nanoparticles, the precise mechanisms of biosynthesis are not well-defined.

Purpose of the Study:

• To investigate the roles of extracellular electron transfer components in palladium (Pd) nanoparticle formation by Shewanella oneidensis.
• To determine how MtrC and flavins influence the rate, structure, and localization of biosynthesized Pd nanoparticles.
• To establish a basis for biologically tailoring nanoparticle catalysts.

Main Methods:

• Genetic manipulation of Shewanella oneidensis to alter expression of electron transfer components.
• Analysis of palladium nanoparticle formation under varying MtrC and flavin availability.
• Characterization of nanoparticle properties (synthesis rate, phenotype, structure, cellular localization).

Main Results:

• Expression and availability of the outer membrane cytochrome MtrC significantly impacted Pd nanoparticle synthesis.
• Soluble redox shuttles (flavins) also played a crucial role in modulating particle formation.
• Modifications in these electron transfer components altered the rate, structure, and cellular localization of Pd nanoparticles.

Conclusions:

• MtrC and flavins are critical factors controlling extracellular electron transfer for Pd nanoparticle biogenesis in Shewanella oneidensis.
• These findings provide a foundation for engineering bacterial strains to produce tailored metal nanoparticle catalysts.
• The identified relationships may be applicable to directing the biogenesis of other metal nanomaterials.