Characterization of a novel electrogenic Clostridium sporogenes isolated from forest soil

Abstract:

[Objective] To identify and characterize an electrogenic bacterium SE6 isolated form forest soil. [Methods] Pure culture of the strain was obtained by anaerobic incubation. It was identified based on morphology, physiology and biochemistry, and 16S rRNA gene sequencing analysis. The strain was inoculated in a dual chamber microbial fuel cell with LB medium as anolyte and potassium ferricyanide as catholyte, to characterize its electrogenic ability. Electrochemical impedance spectroscopy was conducted to analyze internal resistances of the MFCs. Extracellular electron transfer mechanism of the strain was explored by cyclic voltammetry. Biofilm on the anode surface was observed using scanning electron microscope. [Results] The 16S rRNA gene sequence of strain SE6 was 100% phylogenetically related to Clostridium sporogenes. Their morphological, physiological and biochemical characteristics were identical. The maximum power density of the MFCs inoculated with SE6 was 44.42 mW/m². The anodic resistance, cathodic resistance and ohmic resistance were (1488±193) Ω/cm², (0.92±0.01) Ω/cm² and (20.69±1.76) Ω/cm², respectively. Cyclic voltammograms indicated the existence of an electrochemically active substance, of which the peak currents were linearly correlated with the scanning rates. The 1 μm-rodshaped bacteria densely attaching to the anode surface were observed in scanning electron micrographs. [Conclusion] A novel electrogenic strain of C. sporogenes was isolated from forest soil, which transfers electrons extracellularly to electrode with high resistance.