الفهرس 
Nitrate reductase enzymeOnly 14 pages are availabe for public view
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Abstract
In this study. through screening of common bacteria. we report extracellular biosynthesis of metallic silver and gold nanoparticles by the reduction of aqueous Ag + and Au3+ ions using Escherichia coli A TCC 8739, Bacillus subtilis ATCC 6633 Streptococcus thermophilus Esh 1 and Lactobacillus acidophilus DSMZ 20079T cell free extracts as potential candidates for the rapid synthesis of silver and gold nanoparticles. UV-visible spectra show plasmon absorbances of both silver and gold nanoparticles. Transmission electron microscopy (TEM) micrographs showed formation of well-dispersed nanoparticles. X-ray diffraction (XRD) of nanoparticles exhibited 20 values corresponding to values in literature for silver and gold nanocrystals. brIn vitro studies indicated that the formed silver nanoparticles showed variable antimicrobial activity against Escherichia coli, Bacillus subtilis. Salmonella typhimurium, Klebsiella pneumoniae. Staphylococcus aure us and Pseudomonas aeruginosa and fungus like Candida albicans. The diameter of inhibition zone varied according to the silver nanocrystals concentration and the tested microorganism. Gold nanoparticles were used to detect the presence of specific DNA target oligonucleotides. A target oligonucleotide ofhigh CG ratio was chosen in this study, which is a part of the genome sequence in HCV Genotype 4 strain according to Genome Data Base. HCV genotype 4 is highly prevalent in Egypt with more than 19% of the population infected and chronic HCV represents one of the top five leading causes of death due, in part,to ineffective interferon alpha treatment against this genotype. The nanoparticle-based detection protocol was applied in two different probes that would align in a head-to-tail fashion onto the
complementary 20-base target oligonucleotide.