Biosynthesis of silver nanoparticles by Streptomyces hygroscopicus and antimicrobial activity against medically important pathogenic microorganisms

Biological reduction of aqueous silver ions by extracellular components of Strepromyces hygroscopicus has facilitated the development of industrially viable greener methods for the synthesis of technologically important silver nanoparticles (AgNPs). The synthesized aqueous products showed the characteristic absorption spectra at 420 nm, which confirmed the presence of AgNPs. X-ray diffraction patterns displayed typical peaks of crystalline silver at similar to 38 degrees, similar to 45 degrees and similar to 65 degrees. The AgNPs were determined to be spherical (20-30 nm) with a purity of 70% as determined by FE-SEM, TEM, bio-AFM, XRD, and energy dispersive X-ray analysis. Furthermore, the biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic gram-positive bacteria (Bacillus subtilis and Enterococcus faecalis), gram-negative bacteria (Escherichia coli and Salmonella typhimurium) and yeast (Candida albicans). Thus, bioconversion of silver nanoparticles by S. hygroscopicus could be employed as a potential nanomedicine to eliminate pathogenic microorganisms. (C) 2010 Elsevier B.V. All rights reserved.