Hollow particles have attracted considerable attention owing to their unique properties. In this work, hollow zirconia particles were synthesized using rod-shaped gram-negative bacteria, Escherichia coli, as templates. A zirconia precursor, generated by the hydrolysis of zirconium butoxide, was deposited on the surface of the bacterial cells to form the shell of the hollow particles. The as-synthesized particles had the morphology of the bacterial templates, and were about 1.7 mu m long and 0.8 mu m across. The bacterial templates could be removed by calcination at 800 degrees C. The particles shrank on calcination to a final size of about 1.0 mu m long and 0.4 mu m across, with a wall thickness of about 69 nm. The specific surface area and average pore diameter were 45.7 m(2)/g and 1.9 nm, respectively. When fixed cells without internal water were used as templates, no hollow particles were observed; this implies that the internal water inside the cells acted as the initiator for the hydrolysis of zirconium butoxide. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.