Microbial flora composition of microbial fuel cells (MFC) is important to the electricity generation. Four bacterium strains Q1, b, c and d which represent all different morphology of culturable bacterium were isolated from a MFC using 200 mg x L(-1) quinoline as the fuel and operating for at least 210 days. Strains Q1, c and d were Pseudomonas sp. based on 16S rDNA sequence analysis, while strain b was Burkholderia sp. Double-chamber MFCs using 200 mg x L(-1) quinoline and 300 mg x L(-1) glucose as the fuel and potassium ferricyanide as the electron acceptor were constructed. Results showed that strain b, c and d were non-electrogenesis. The electrical charges of MFC inoculated electrogenesis strain Q1 with non-electrogenesis strain b, c and d respectively were 3.00, 3.57 and 5.13C, and the columbic efficiency were 3.85%, 4.59% and 6.58%, which were all lower than that inoculated with pure Q1, because of the interspecific competition of electrogenesis and non-electrogenesis bacteria. Combinations of Q1 with the other three strains respectively resulted in 100% of quinoline degradation rates within 24h, which is better than pure cultures, that is, mixed microbial populations perform better in MFC when complex organics are used as the fuel. GC/MS analyses showed that only 2(1H)-quinolinone and phenol existed in the effluent of the MFC, which was inoculated with only Q1 or mixed bacteria.