Revealing the role of Geobacter in regulating the microbial community during microbial electrochemical systems operation

Geobacter is frequently used as an indicator to assess the maturity of electroactive biofilm (EAB), which is the core of microbial electrochemical systems (MESs) converting chemical energy in wastewater to electricity. It is still unclear how Geobacter influence the EABs formation and microbial community succession during MESs operation. In this study, we found that Geobacter in inoculum affected EABs formation during MESs start-up. The maximum output current density of group added 5 % Geobacter in inoculum (G5) was 3 times to that of group only inoculated by domestic wastewater (G0) at the end of the first cycle. Besides, the proportion of Geobecter in EAB increased to 66.6 % in group G5 which was 2.4 times to that of G0. Even after a long period of operation, the quantity and proportion of electroactive microorganisms were kept well in Geobacter inoculated groups, with a 50 % higher percentage of G19 relative to G0. Extracellular polymeric substance facilitating biofilm formation in G5 was also much more abundant than that in G0. Moreover, Geobacter with higher proportion in inoculum demonstrated higher gene copies related to pili, flagellum and chemotaxis in the EABs. The biofilms of the groups with a small amount addition of Geobacter developed and matured faster. Our findings demonstrated that EABs microbial community during start-up stage could be affected by regulating the proportion of Geobacter in inoculum, suggesting a manageable strategy to obtain mature EABs quickly.