A green chemical synthesis of silver nanoparticles (AgNPs) through in situ reduction of silver nitrate (AgNO3) by a fungal strain of Rhizopus oryzae is described along with the promising eco-friendly role of the synthesized nano-silver bioconjugate (NSBC) material in water purification process. The NSBC has been characterized using UV-vis spectroscopy, high resolution transmission electron (HRTEM) microscopy, and Fourier transform infrared (FTIR) spectroscopy. The NSBC exhibits strong antibacterial activity against Escherichia coli and Bacillus subtilis and high adsorption capacity towards different organophosphorous pesticides. Fluorescence and electron microscopic images reveal NSBC binds on the bacterial cell wall, which cause irreversible membrane damage eventually leading to cell death. Proteomic analysis further demonstrates down regulation of protein expression, inhibition of cytosolic and membrane proteins and leakage of cellular content following binding of NSBC with bacterial cell wall. NSBC has been exploited to obtain potable water free from pathogens and pesticides in one step process. (C) 2012 Elsevier Ltd. All rights reserved.