Microbial components of the microbial fuel cells (MFCs), including species constitution and metabolic mechanism of the anodic microorganisms, are critical to the optimization of electricity generation. An electrogenesis baterium strain (designated as RE7) was isolated from an MFC that had been running in a fed batch mode for over one year. The isolate was identified as a strain of Pseudomonas aeruginosa based on its physiological, morphological characteristics and 16S rRNA sequence analysis. Direct electron transfer from RE7 to an electrode was examined using cyclic voltammetry and MFC. Results of both methods showed the electrochemical activity of the bacterium without any electrochemical mediator. The P. aeruginosa strain RE7 was inoculated into the anode chamber of a packing-type MFC and the maximal voltage output was 352 mV with 1 500 mg/L glucose as the fuel. Correspondingly, the maximal area and volumetric power densities were 69.2 mW/m2 and 6.2 W/m3, respectively. Bacteria-producing soluble redox mediators, such as phenazine derivatives, are possible mechanism to facilitate the direct electron transfer to the electrode from the bacterial cells.