PNNL

Abstract

Direct interspecies electron transfer (DIET) has been considered as a novel and highly efficient strategy in both natural anaerobic envi-ronments and artificial microbial fuel cells. A syntrophic model consisting of Geobacter metallireducens and Geobacter sulfurre-ducens was studied in this work. We conducted in vivo molecular mapping of the outer surface of the syntrophic community as the interface of nutrients and energy exchange. System for Analysis at the Liquid Vacuum Interface (SALVI) combined with time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed to capture the molecular distribution of syntrophic Geobacter com-munities in the living and hydrated state. Principal component analysis (PCA) with selected peaks revealed that syntrophic Geo-bacter aggregates were well differentiated from other control sam-ples, including syntrophic planktonic cells, pure cultured planktonic cells, and single population biofilms. Our in vivo imaging indicated that a unique molecular surface was formed. Specifically, aromatic amino acids, phosphatidylethanolamine (PE) components, and large water clusters were identified as key components that favored the DIET of syntrophic Geobacter aggregates. Moreover, the molecu-lar changes in depths of the Geobacter aggregates were captured using dynamic depth profiling. Our findings shed new light on the interface components supporting electron transfer in syntrophic communities based on in vivo molecular imaging.