Microbial community dynamics in MFCs

38 The performance and dynamics of the bacterial communities in the biofilm and suspended 39 culture in the anode chamber of sucrose-fed microbial fuel cells (MFCs) were studied by using 40 Denaturing Gradient Gel Electrophoresis (DGGE) of PCR-amplified partial 16S rRNA genes 41 followed by species identification by sequencing. The power density of MFCs was correlated to 42 the relative proportions of species obtained from DGGE analysis in order to detect bacterial 43 species or taxonomic classes with important functional role in electricity production. Although 44 replicate MFCs showed similarity in performance, cluster analysis of DGGE profiles revealed 45 differences in the evolution of bacterial communities between replicate MFCs. No correlation 46 was found between the proportion trends of specific species and the enhancement of power 47 output. However, in all MFCs putative exoelectrogenic denitrifiers and sulphate-reducers 48 accounted for approximately 24% of the bacterial biofilm community at the end of the study. 49 Pareto-Lorenz evenness distribution curves extracted from the DGGE patterns obtained from 50 time-course samples indicated community structures where shifts between functionally similar 51 species occur, as observed within the predominant fermentative bacteria. These results suggest 52 the presence of functional redundancy within the anodic communities, a probable indication that 53 stable MFC performance can be maintained in changing environmental conditions. The 54 capability of bacteria to adapt to electricity generation might be present among a wide range of 55 bacteria. 56