Using electrical signals of microbial fuel cells to detect copper stress on soil microorganisms

摘要

A method based on microbial fuel cells (MFCs) was used to evaluate the effects of copper (Cu2+) on soil microorganisms. Soil spiked with 50-400mgkg(-1) of Cu2+ as CuCl2 was incubated for 24hours before being packed into the MFC anode chambers and assayed for dehydrogenase activity (DHA), substrate-induced respiration (SIR) and microbial biomass carbon (C-mic). Soil was amended with 5% (w/w) glucose to accelerate start-up' and improve power generation, followed by 150hours of operation. Anode biofilm and soil was extracted to recover total nucleic acids and the 16S rRNA gene was subjected to PCR-DGGE, sequencing and phylogenetic analysis. Results showed that increases in soil Cu2+ concentrations reduced voltage and postponed start-up. The quantity of generated electrons within 48hours was 32.5 coulomb (C) in the without-Cu control and decreased with increasing Cu2+ concentrations (11.7, 7.7, 2.0 and 1.3C under 50, 100, 200 and 400mgkg(-1)Cu(2+), respectively). Cyclic voltammetry identified decreased soil electrochemical activity with increasing Cu2+ concentrations. The results indicate that Cu2+ reduced electrical signals by inhibiting the electrochemical activity, metabolic activity and biomass of microorganisms. The 16S sequences of recovered anodic bacteria were assigned to Firmicutes, including Bacillaceae, Acetobacteraceae, Clostridium, Bacillus and Sporolactobacillus. In general, the DGGE band intensity of anodic bacteria decreased with increasing Cu2+ concentrations, except for bands assigned to Firmicutes and Bacillus, which increased with increasing Cu2+ concentrations. We suggest that the short-term electrical signals generated from MFCs with contaminated soil can be used to assess the toxic effect of heavy metal pollutants on soil microorganisms.