Metabolic Characteristics of a Glucose-Utilizing Shewanella oneidensis Strain Grown under Electrode-Respiring Conditions

• Published in: PloS one 2015-09, Vol.10 (9), p.e0138813-e0138813
• Main Authors: Nakagawa, Gen, Kouzuma, Atsushi, Hirose, Atsumi, Kasai, Takuya, Yoshida, Gen, Watanabe, Kazuya
• Format: Article
• Language: English
• Subjects: Acetates - metabolism; Acetic acid; Bacteriological Techniques - instrumentation; Bacteriological Techniques - methods; Bioreactors; Bioreactors - microbiology; Carbohydrates; Carbon; E coli; Electric properties; Electrochemical Techniques - instrumentation; Electrochemical Techniques - methods; Electrochemistry; Electrode potentials; Electrodes; Energy Metabolism; Escherichia coli; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fermentation; Fuel cells; Gene expression; Gene Expression Regulation, Bacterial; Genetic Engineering; Genomes; Glucose; Glucose - metabolism; Glucose kinase; Lactates; Lactates - metabolism; Lactic acid; Life sciences; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Metabolic Networks and Pathways - genetics; Metabolic pathways; Metabolism; Metabolites; Microorganisms; Oxidation-Reduction; Permease; Pharmacy; Phosphotransferases - genetics; Phosphotransferases - metabolism; Pyruvic acid; Reactors; Respiration; Reverse Transcriptase Polymerase Chain Reaction; Shewanella - genetics; Shewanella - metabolism; Silver chloride; Sugar; Transcription; Transcription (Genetics)
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0138813

In bioelectrochemical systems, the electrode potential is an important parameter affecting the electron flow between electrodes and microbes and microbial metabolic activities. Here, we investigated the metabolic characteristics of a glucose-utilizing strain of engineered Shewanella oneidensis under electrode-respiring conditions in electrochemical reactors for gaining insight into how metabolic pathways in electrochemically active bacteria are affected by the electrode potential. When an electrochemical reactor was operated with its working electrode poised at +0.4 V (vs. an Ag/AgCl reference electrode), the engineered S. oneidensis strain, carrying a plasmid encoding a sugar permease and glucose kinase of Escherichia coli, generated current by oxidizing glucose to acetate and produced D-lactate as an intermediate metabolite. However, D-lactate accumulation was not observed when the engineered strain was grown with a working electrode poised at 0 V. We also found that transcription of genes involved in pyruvate and D-lactate metabolisms was upregulated at a high electrode potential compared with their transcription at a low electrode potential. These results suggest that the carbon catabolic pathway of S. oneidensis can be modified by controlling the potential of a working electrode in an electrochemical bioreactor.