Corynebacterium strain SH09 separated from a silver mine was used for biosorption and bioreduction of diamine silver complex. The biosorption of the diamine silver complex was better than that of silver ions and the maximum of the former was about 350 (mg Ag) (g dried biomass)(-1). After dried cells of SH09 were resuspended in the aqueous solution of diamine silver complex in the dark at 60degreesC for more than 72 h, transmission electron microscopy (TEM) observations showed that a large quantity of black particles whose diameter ranged from 10 to 15 nm were formed on the cell wall. The particles were identified as being silver nanoparticles by X-ray diffraction (XRD) and UV-vis spectroscopy. Under the same conditions, no bioreduction of silver nitrate was found. According to IR spectra, some functional groups, such as the amide of the proteins, were involved in the processes of biosorption and bioreduction. (C) 2004 Society of Chemical Industry.