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The microbial sources used for the production of nanoparticles are important, and one of the reasons for bacterial preference is their ease of manipulation and ecofriendly potential. Three bacteria strains of Streptomyces genus were used for the biosynthesis of silver nanoparticles (AgNPs). The aim of the present study was to confirm Streptomyces spp. as biological systems in the synthesis and extracellular characterization of silver nanoparticles with antimicrobial activity. The nanoparticles were characterized by ultraviolet–visible spectroscopy (UV-Vis), dynamic light scattering (DLS), RDX, Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). In qualitative antimicrobial test, Streptomyces parvulus DPUA 1549 and Streptomyces owasiensis DPUA 1748 showed activity against pathogenic microorganisms (bacteria and yeasts) tested. The AgNPs of S. parvulus DPUA 1549 showed the most efficient minimum inhibitory concentration (MIC) at low concentrations (1.95 μM) against Staphylococcus aureus. They promoted structural damage to the micro-organism cell surface according to AFM images and also reduced the proliferation of NIH-3T3 cells in the cytotoxic assay. Thus, biosynthesis of silver nanoparticles by Streptomyces spp. is a potential source to be used in nanomedicine and cosmetology industries. Key words: Streptomyces, tropical region, nanobiotechnology, antimicrobial, cytotoxic test.