Production and antimicrobial activity of silver nanoparticles synthesized from indigenously isolated Pseudomonas aeruginosa from Rhizosphere.

Nanoparticles hold profound biological, pharmaceutical and industrial applications. Green synthesis of nanoparticles is considered amongst the environmentally safe and cost effective method of nanoparticle synthesis. Briefly, Pseudomonas strains were isolated from rhizosphere soil samples. Cell free supernatants of 36% of the isolates showed production of silver nanoparticles. Of these, three isolates, SMS13, SMS100 and SMS124 were selected as the potentially best nanoparticle producers. Amplification and DNA sequencing of 16srRNA gene identified all three strains as Pseudomonas aeruginosa. Scanning electron microscopy showed existence of particles between the ranges of 60nm to 70nm in the diameter with elemental composition of silver varies from 0.48% to 1.61%. Consistently, surface plasmon resonance showed maximum absorbance of nanoparticles between 352nm to 406nm. Finally, antibacterial activity of the synthesized nanoparticles was assessed by spot assay whereas Cell Free Supernatants (CFS) of respective isolates were taken as control against clinical isolates of Salmonella typhi, Shigella dysentriae, Klebsiella pneumoniae, P. aeruginosa, Proteus mirabilis and Streptococcus epidermidis. Nanoparticles suspension from all isolates exhibited antibacterial activity against all the screened isolates, whereas no biological activity was observed in the CFS of corresponding strains.