9 ± 0.2    Pseudomonas aeruginosa – - 0.8 ± 0.1    Shewanella oneidensis – - 0.7 ± 0.1 During the pure culture continuous experiments, G. sulfurreducens and S. oneidensis initially showed very similar AZD8186 concentration development, although slower than P. aeruginosa, with small towers averaging

a height of 8 μm and diameters between 10-20 μm. Moreover, the biofilms became less dense with higher towers developing while prolonged this website biofilm development revealed less coverage of the electrode giving way to the formation of channels and loss of biofilm mass, similar to that observed in the P. aeruginosa biofilm (Figure 3). Additionally, a few towers reaching 50 μm in height were observed in the G. sulfurreducens biofilm while the S. oneidensis biofilm revealed an occasional tower structure up to 45 μm dispersed throughout the biofilm. These results also correlated with the high level of roughness coefficient measurement from COMSTAT (Table 2) again indicating the non-uniformity of these biofilms throughout Bucladesine ic50 the duration of the continuous pure culture experiment. Figure 3 SEM images of P. aeruginosa biofilms at A. 72 hours (3000 ×) and B. 144 hours (3000 ×) during continuous mode. During continuous mode the G+ C. acetobutylicum and E. faecium biofilms started out slowly and similarly with only small (5 μm high) aggregates of biofilm growth on the electrode. These biofilms

did not increase in height like the G- and as time progressed the heights of these biofilms remained low (7-14 μm). By the end of 144 Casein kinase 1 hours the biofilms highest point reached 15 μm, with colony diameters of less than 10 μm. A more detailed description of the pure culture continuous experiments can be seen in Additional file 2. Roughness coefficients for G+ during continuous experiments were higher than those of the batch experiments (Table 2) indicating more non-uniformity during the continuous experiments. The continuously fed MFCs revealed the G- consistently generating more current than the G+ (Figure 4). P. aeruginosa reached its peak in current production

(0.5 ± 0.01 mA) between 24-48 hours, however, by 144 hours it had decreased to 0.14 ± 0.01 mA. G. sulfurreducens and S. oneidensis, on the other hand, both increased current generation later in the experiment while the G+ E. faecium and C. acetobutylicum maintained a low current throughout. Figure 4 Pure culture continuous experiment showing Current (mA) vs Time (hours). Circle: G. sulfurreducens, Square: P. aeruginosa, Upright triangle: S. oneidensis, Upsidedown triangle: E. faecium and Diamond: C. acetobutylicum During the continuous co-culture experiments, E. faecium remained in the close vicinity of the electrode while the G- colonized the top of the biofilm. As time progressed they separated with the G- forming towers and E. faecium developed a lawn over the electrode surrounding the G-. Confocal microscopy revealed large towers of P. aeruginosa (40 ± 10 μm) surrounded by a lawn of E. faecium (Figure 5A).