Comparative transcriptomics of closely related Geobacter sulfurreducens strains

Members of Geobacter sulfurreducens are electroactive bacteria that transfer electrons to extracellular solid electron acceptors using extracellular electron transport pathways, thereby generating currents in bioelectrochemical systems (BESs). Different G. sulfurreducens strains generate varying current levels in BESs, but little is known about the molecular mechanisms underlying strain-level variation in current generation. The present work comparatively analyzed G. sulfurreducens strains OSK2A and 60473, which were identified as closely related in phylogenomic analyses. Comparative transcriptomics shows that expression levels of genes encoding extracellular proteins, including pili and nanowires, in the EET pathways differ substantially between these strains, whereas those for catabolic enzymes are relatively similar. These results suggest that differences in current generation among G. sulfurreducens strains are attributable to differences in the expression of genes encoding extracellular proteins in the EET pathway.