Combined effects of enrichment procedure and non-fermentable acetate or fermentable glucose on system performance and bacterial community for pentachlorophenol (PCP) degradation in microbial fuel cells (MFCs) were determined in this study. Co-substrate and PCP were added into MFCs either simultaneously or sequentially. Simultaneous addition with glucose (simultaneous-glucose) achieved the shortest acclimation time and the most endurance to heavy PCP shock loads. Species of Alphaproteobacteria (simultaneous-acetate, 33.9%; sequential-acetate, 31.3%), Gammaproteobacteria (simultaneous-glucose, 44.1%) and Firmicutes (sequential-glucose, 31.8%) dominated the complex systems. The genus Sedimentibacter was found to exist in all the cases whereas Spirochaetes were merely developed in simultaneous-acetate and simultaneous-glucose. While Epsilonproteobacteria were only absent from sequential-acetate, simultaneous-glucose benefited to the evolution of Lentisphaerae. These results demonstrate simultaneous-glucose is a strategy for efficient system performance and the microbiological evidence can contribute to improving understanding of and optimizing PCP degradation in MFCs. (C) 2012 Elsevier Ltd. All rights reserved.