Biofilm viability increases closer to the anode when the electrode is active. Adjacent CLSM images (20 ×) are both 72 hour side-views of S. oneidensis biofilms from batch experiment detected Opaganib mw using the Live/Dead (baclight) stain. Circle: G. sulfurreducens, Square: P. aeruginosa, Upright triangle: S. oneidensis, Upsidedown triangle: E. faeciumand Diamond: C. acetobutylicum Development and current generation of pure and co-culture anode biofilms During the pure culture closed circuit experiments the heights of the biofilms

were less than that of the open circuit experiments (Table 1). For example, the biofilm height of P. aeruginosa was 30 ± 3 μm for the closed circuit experiment and 42 ± 3 μm for the open circuit experiment, as calculated with COMSTAT. All G- cultures developed an ample coverage of the electrode within the three ay period both in closed and open circuit. For example, the S. oneidensis biofilm formed large towers of 40 μm high and up to ~50 μm in diameter while the G+ species developed smaller microcolonies with the odd tower up to 20 μm high and 10-20 μm

in diameter (during closed circuit). The latter was also reflected in the higher roughness coefficient between the G- and G+ biofilms indicating find more that during batch mode the G+ are flatter and more uniform than the G- (Table 2). During these pure culture batch experiments G+ species delivered low current throughout while the G- produced a much higher current as shown in Table 1. Table 1 Comparison of current generation

and biofilm heights in pure and co-cultures.   Imax (mA) Maximum Biofilm thickness (μm, batch)-COMSTAT   Continuous Batch Closed circuit anode Open circuit anode Pure culture experiments    Geobacter sulfurreducens 1.1 ± 0.06 1.0 ± 0.05 25 ± 6 49 ± 5    Pseudomonas aeruginosa 0.5 ± 0.01 0.9 ± 0.01 30 ± 3 42 ± 3    Shewanella oneidensis 1.3 ± 0.05 1.0 ± 0.15 26 ± 2 41 ± 3 PJ34 HCl    Clostridium acetobutylicum 0.13 ± 0.006 0.1 ± 0.03 14 ± 6 24 ± 6    Enterococcus faecium 0.1 ± 0.05 0.2 ± 0.05 18 ± 3 23 ± 4 Co-cultures with Enterococcus faecium    Geobacter sulfurreducens 1.9 ± 0.03 – 50 ± 7 –    Pseudomonas aeruginosa 1.8 ± 0.04 – 40 ± 4 –    Shewanella oneidensis 2.0 ± 0.06 – 39 ± 7 – Co-cultures with Clostridium acetobutylicum    Geobacter sulfurreducens 0.1 ± 0.03 – 7 ± 3 –    Pseudomonas aeruginosa 0.3 ± 0.05 – 8 ± 2 –    Shewanella oneidensis 0.2 ± 0.06 – 5 ± 1 – Table 2 Roughness coefficients of biofilms determine by COMSTAT.   Roughness Coefficient -Batch Roughness Coefficient -continuous   Closed circuit anode Open circuit anode   Pure culture experiments    Geobacter sulfurreducens 1.8 ± 0.3 1.0 ± 0.4 1.8 ± 0.2    Pseudomonas aeruginosa 1.8 ± 0.5 1.1 ± 0.2 1.9 ± 0.1    Shewanella oneidensis 1.7 ± 0.2 0.9 ± 0.3 1.9 ± 0.3    Clostridium acetobutylicum 1.5 ± 0.3 1.2 ± 0.3 1.7 ± 0.2    Enterococcus faecium 1.4 ± 0.2 1.2 ± 0.2 1.9 ± 0.