Electrochemically active bacteria sense electrode potentials for regulating catabolic pathways

Electrochemically active bacteria (EAB) receive considerable attention for their utility in bioelectrochemical processes. Although electrode potentials are known to affect the metabolic activity of EAB, it is unclear whether EAB are able to sense and respond to electrode potentials. Here, we show that, in the presence of a high-potential electrode, a model EAB Shewanella oneidensis MR-1 can utilize NADH-dependent catabolic pathways and a background formate-dependent pathway to achieve high growth yield. We also show that an Arc regulatory system is involved in sensing electrode potentials and regulating the expression of catabolic genes, including those for NADH dehydrogenase. We suggest that these findings may facilitate the use of EAB in biotechnological processes and offer the molecular bases for their ecological strategies in natural habitats. A single-chambered EC (electrochemical cell) was used for analyzing transcriptomes of wild-type (WT) and ∆arcS strains. The working electrode was poised at +0.2 V until the electric current became stable (for approximately 15 h), and then the potential was changed to +0.5 V (high potential; HP) or –0.1 V (low potential; LP). After further cultivation in the ECs for 2 h, the bacterial cells attached to the working electrode were collected and subjected to RNA extraction. For the transcriptome analysis of WT strain, five biological replicates were prepared from independent ECs (n = 5). For the analysis of ∆arcS, three biological and two technical replicates were prepared (n = 6). Transcriptomic profiles in each strain were compared between the two potential conditions (HP and LP; total 22 samples).