Table of Contents
ISRN Nanotechnology
Volume 2011, Article ID 385480, 7 pages
http://dx.doi.org/10.5402/2011/385480
Research Article

Extracellular Biosynthesis of Silver Nanoparticles Using Escherichia coli ATCC 8739, Bacillus subtilis ATCC 6633, and Streptococcus thermophilus ESh1 and Their Antimicrobial Activities

1Bacteriology Unit, Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt
2Biotechnology Department, Faculty of Science, Taif University, P.O. Box 888, Taif 21974, Saudi Arabia
3Biological Sciences Department, Faculty of Science and Art, King Abdulaziz University, Rabigh Campus, P.O. Box 344, Rabigh 21911, Saudi Arabia

Received 26 April 2011; Accepted 2 June 2011

Academic Editors: R. Jin and Y. Joseph

Copyright © 2011 Abd El-Raheem R. El-Shanshoury et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The development of reliable and eco-friendly organisms of silver nanomaterials is an important aspect of current nanotechnology research and application. Recently, microorganisms have been explored as potential biofactory for synthesis of silver nanoparticles. In this study, through screening of common bacteria, we report extracellular biosynthesis of metallic silver nanoparticles by the reduction of aqueous Ag+ using Escherichia coli ATCC 8739, Bacillus subtilis ATCC 6633, and Streptococcus thermophilus ESh1 as potential candidates for the rapid synthesis of silver nanoparticles. The culture supernatant of silver nanoparticles biosynthesis by reduction of silver ion coming in contact with the cell filtrate was fast and was formed within few minutes. UV-visible spectrum of the aqueous media obtained from the above bacteria containing silver ion showed a peak around 420 nm corresponding to the plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) micrographs showed formation of well-dispersed silver nanoparticles in the range of 5–25 nm. X-ray diffraction (XRD) of silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal. In vitro studies indicated that the formed silver nanoparticles showed variable antimicrobial activity against Escherichia coli, Bacillus subtilis, Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa and the fungus like yeast (Candida albicans). The diameter of inhibition zone varied according to the silver nanocrystal concentration and the test microorganism.