We co-cultured I. sakaiensis with G. sulfurreducens in a bio-electrochemical reactor, where I. sakaiensis supplies acetate from fermentation of PET or EG to G. sulfurreducens for electricity production (Figure ). The bio-electrochemical reactor consisted of a three-electrode system with a Ag/AgCl reference electrode, a Pt mesh counter electrode, and an IO-ITO working electrode (Figure ). The IO-ITO electrode served as a host structure for the G. sulfurreducens biofilm and had a geometrical surface area of 0.25 cm 2 , a thickness of 40-45 µm, and a macropore size of 8-10 µm . In the first step towards establishing the artificial co-culture, we grew an electrochemically active G. sulfurreducens biofilm on the IO-ITO electrode (IO-ITO|G. sulfurreducens) following a previously published procedure (39) using G. sulfurreducens as the inoculum (OD600 = 0.6) and acetate (20 mM) as the sole carbon source in bicarbonatebuffered complex medium by poising an applied potential of 0.1 V vs. standard hydrogen electrode (SHE). A current plateau at 1.7 mA cm -2 was observed after 3 d (Figure ), indicating that G. sulfurreducens has colonized on the electrode while metabolizing acetate to CO2 . In the second step, the bicarbonate-buffered complex medium was replenished with fresh medium (without acetate and planktonic G. sulfurreducens) and then I. sakaiensis was added (OD600 = 0.6) together with PET films (60 mg) or EG (25 mM) as the sole substrate to the bio-electrochemical reactor containing the IO-ITO|G. sulfurreducens electrode. The bio-electrochemical system with PET as the sole substrate showed a maximum current density of 0.6 mA cm -2 while EG as the substrate showed a current density of 1.7 mA cm -2 (Figure ). The lower current from PET compared to EG is attributed to the slower hydrolysis step for the insoluble synthetic polymer. Current production started to decay after an initial peak current for both PET and EG (Figure ), which is commonly observed in microbial fuel cells and an indication for a limitation in acetate supply .