Due to the unique features of the nanoparticles, they are applying in biotechnology, medical imaging and catalysts. Silver nanoparticles (AgNPs) are among the most widely used nanoparticles that show a broad spectrum of antibacterial and antiviral activity. Production of silver nanoparticles by psychrotolerant strain of OSIP1 and antibacterial properties was investigated. The strain was cultured in TSB medium and incubated at 20 °C for 3 days. 1 mM silver nitrate solution was added to the supernatant of medium culture. The colorless solution of silver nitrate changed to deep brown, indicating the formation of AgNPs. The UV-visible and XRD spectroscopy were used to determine the purity and size of the nanoparticle. The antimicrobial property of silver nanoparticles was evaluated using ELISA. The antibacterial activity of biosynthesized AgNPs was tested on two pathogenic bacteria namely Pseudomonas aeruginosa and Bacillus subtilis. The tested bacteria were exposed to different concentrations of biosynthesized AgNPs (ranging from 1000 to 1.9 µg/ml) in Muller Hinton broth medium and incubated at of 37 °C for 24 hours. The results showed one peak (400-500 nm) was detected for silver nanoparticles in the UV-visible spectrometer indicated the presence of silver nanocrystals. This result was proved using the XRD method with nanocrystals size of 22 nm. Silver nanoparticles have a minimum inhibitory concentration (MIC) of 250 µg/ml and 31.25 µg/ml for Pseudomonas aeruginosa and Bacillus subtilis, respectively. This eco-friendly method could be an alternative method for synthesis of green nanoparticle and thus has a potential to use in biomedical applications.

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