New applications of nanomaterials are rapidly emerging. The synthesis of nanoparticles is a cornerstone of nanotechnology. Microbial cells are highly-organized units, regarding morphology and metabolic pathways, capable of synthesizing well size-calibrated and well-structured particles. Furthermore, biogenic nanoparticles often are water-soluble and biocompatible, which is essential for many applications. Molecular identification of a novel strain P. fluorescens BCPBMS-1 from sponge Callysspongia diffusa  (Mandapam Coast) through 16s rRNA ribotyping (Gen bank accession number: HQ907732). The silver nanoparticles were analyzed by UV-Visible spectroscopy. Their chemical composition was determined by FT-IR spectroscopy. SEM observationrevealed that silver nano particles are having spherical shape. The antibacterial activities of silver nanoparticles were screened against common human pathogen Escherichia coli, Proteus mirabilis, Salmonella typhi, Salmonella paratyphi, Vibrio cholerae, Klebsiella oxytoca, Klebsiella pneumoniae and Staphylococcus aureus.Among these5mm antibacterial activity was observed with E. coli, 4mm with P. mirabilis and S. typhi, 3mm activity was observed with S. paratyphi.These results suggest that Ag nanoparticles can be used as effective growth inhibitors in various microorganisms, making them applicable to diverse medical devices and antimicrobial control systems.