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Spatio-temporal development of the bacterial community in a tubular longitudinal microbial fuel cell

The spatio-temporal development of a bacterial community in an exoelectrogenic biofilm was investigated in sucrose-fed longitudinal tubular microbial fuel cell reactors, consisting of two serially connected modules. The proportional changes in the microbial community composition were assessed by PCR-DGGE and DNA sequencing in order to relate them to the performance and stability of the bioelectrochemical system. The reproducibility of duplicated reactors, evaluated by cluster analysis and Jaccard’s coefficient, shows 80-90% similarity in species composition. Biofilm development through fed-batch start-up and subsequent stable continuous operation results in a population shift from (-Proteobacteriaand Bacteroidetesto Firmicutesdominated communities, with other diverse species present at much lower relative proportions. DGGE patterns were analyzed by Range-weighted richness (Rr) and Pareto-Lorenz evenness distribution curves to investigate the evolution of the bacterial community. The first modules shifted from dominance by species closely related to B. graminisolvens, R. ornithinolytica and Klebsiella sp. BM21 at the start of continuous-mode operation, to a community dominated by P. propionicigenes, Lactococcus sp., P. agglomerans and K. oxytoca related species with stable power generation (6.0 W/m3) at day 97. Operational strategies that consider the dynamics of the population will provide useful parameters for evaluating system performance in the practical application of MFCs.