The Bacillus fusiformis (BFN) strain and its biodegradation of phenol when iron-based nanoparticles such as nanoscale zero-valent iron (nZVI) and Ni/Fe nanoparticles (Ni/Fe) were present at different pH values (6.0, 8.0, and 3.0) were investigated. The growth of BFN and its biodegradation of phenol accelerated in the presence of nZVI and Ni/Fe both at pH 8.0 and pH 6.0. The H-2 generated by the corrosion of iron can be used as an electron donor and source of energy for growing BFN. However, only nZVI improved the biodegradation of phenol at pH 3.0, which is most likely due to the increasing medium pH value resulting from the generation of OH- as a result of iron corrosion. The images from scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) demonstrated that these iron-based nanoparticles adhered to the surface of BFN, but no significant change in the morphology of BFN was observed. (C) 2013 Elsevier Ltd. All rights reserved.