Characterization of syntrophic Geobacter communities using ToF-SIMS

Area of Science:

• Microbiology
• Biogeochemistry
• Surface Science

Background:

• Direct interspecies electron transfer (DIET) is crucial for microbial consortia function.
• The surface chemical speciation of syntrophic Geobacter aggregates involved in DIET remains largely uncharacterized.

Purpose of the Study:

• To investigate the surface chemical composition of syntrophic Geobacter metallireducens and Geobacter sulfurreducens aggregates.
• To elucidate the role of surface chemistry in facilitating direct interspecies electron transfer (DIET).

Main Methods:

• Utilized surface-sensitive time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze microbial aggregates.
• Employed principal component analysis (PCA) for spectral data analysis.

Main Results:

• Syntrophic Geobacter aggregates displayed distinct surface chemical compositions compared to planktonic cells, notably enriched in amino acids, fatty acids, and lipids.
• Amino acid fragments were major contributors to spectral variance, highlighting the significance of proteins in aggregate formation.
• The quorum sensing molecule N-butyryl-l-homoserine lactone was detected, suggesting its role in syntrophic interactions and aggregation.
• Geobacter sulfurreducens was identified as the dominant species driving syntrophic growth in the aggregates.

Conclusions:

• Unique surface chemistry distinguishes syntrophic Geobacter aggregates from planktonic cells.
• Proteins and quorum sensing molecules play key roles in the formation and function of syntrophic aggregates.
• ToF-SIMS is a valuable tool for studying DIET mechanisms and interspecies electron transfer in biofilms.