The biomass of Aeromonas SH10 was proven to strongly absorb Ag+ and [Ag (NH3)(2)](+). The maximum uptake of [ Ag( NH3)(2)](+) was 0.23 g( Ag) g(-1)( cell dry weight), higher than that of Ag+. Fourier transform infrared spectroscopy spectra analysis indicated that some organic groups, such as amide and ionized carboxyl in the cell wall, played an important role in the process of biosorption. After SH10 cells were suspended in the aqueous solution of [ Ag( NH3)(2)]+ under 60 degrees C for more than 12 h, [Ag( NH3)(2)](+) was reduced to Ag( 0), which was demonstrated by the characteristic absorbance peak of elemental silver nanoparticle in UV-VIS spectrum. Scanning electron microscopy and transmission electron microscopy observation showed that nanoparticles were formed on the cell wall after reduction. These particles were then confirmed to be elemental silver crystal by energy dispersive X-ray spectroscopy, X-ray diffraction, and UV-VIS analysis. This study demonstrated the potential use of Aeromonas SH10 in silver-containing wastewater treatment due to its high silver biosorption ability, and the potential application of bioreduction of [Ag( NH3)(2)](+) in nanoparticle preparation technology.