The study of mediator enhanced microbial extracellular electron transfer by constructing a soil bioelectrochemical system

Baoli Qin^a,b, Y. Wu^a and T. Liu^a

^a Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, China

^b College of Environmental Science and Engineering, Taiyuan University of Technology, China

1311565825@qq.com

Microbial extracellular electron transfer (EET) is an important driving force for biogeochemical cycling of elements in soil. Electron mediators can stimulate the biofilm formation of Shewanella MR-1 so that enhanced the EET process. However, the way mediators influence the biofilm formation in a soil system is still unknown. Bioelectrochemical system (BES) is a promising technic to examine the in situ dynamics of EET by directly recording the microbial current generation. Hence, the effect of mediator was investigated in a soil BES, using 50 μM of 9,10-anthraquinone-2-sulfonic acid (AQS) as electron mediator. Results show that current generation was increased by AQS, implying an enhanced EET rate. The biofilm biomass, as indicated by the total protein extracted from the electrode, also increased. AQS changed the biofilm microbial community. 16s rDNA results show that Geobacter has the highest proportion in the system without AQS, while it substantially decreased in the system with AQS. Chao1 index increased in the system with AQS, suggesting that AQS promoted the microbial diversity. This change of community probably has contribution to the enhancing of biofilm formation. In summary, a new technic of soil BES was constructed in this study, and it demonstrated that AQS has the ability to enhance the EET process in a soil system via stimulating biofilm formation and changing microbial community.