This study demonstrated electricity generation in a thermophilic microbial fuel cell (MFC) operated on synthesis gas (syngas) as the sole electron donor. At 50 degrees C, a volumetric power output of 30-35 mW L-R(-1) and a syngas conversion efficiency of 87-98% was achieved. The observed pathway of syngas conversion to electricity primarily consisted of a two-step process, where the carbon monoxide and hydrogen were first converted to acetate, which was then consumed by the anodophilic bacteria to produce electricity. A denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rDNA revealed the presence of Geobacter species, Acetobacter, methanogens and several uncultured bacteria and archaea in the anodic chamber. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.