الفهرس 
LITERATURE OF REVIEWOnly 14 pages are availabe for public view
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Abstract
This work has been carried out to investigate the ability of some bacterial isolates from gold and silver workshops in Jewish Quarter , El-sagha , Cairo , Egypt for synthesis of silver nanoparticles extracellularly. The results improved that 7 bacterial isolates (MAM-S3, MAM-S5, MAM-S6, MAM-S7, MAM-S8, MAM-S17, MAM-S18) have the ability to produce silver nanoparticles extracellularly. The most potent bacterial isolates for production of AgNPs were MAM-S17 and MAM-S18. These two bacterial isolates were identified by 16 S rRNA as Lysinibacillus fusiformis MAM-S17 with accession No. MN900609 and Brevundimonas naejangsanensis MAM-S18 with accession No. MN922643 . Factors affecting AgNPs production (AgNO3 concentrations , pH values , Incubation temperatures and Incubation periods) were investigated . The bacterial isolate MAM-S17 has the ability to produce AgNPs extracellularly. The results revealed that the maximum AgNPs production by the bacterial isolate MAM-S17 were recorded at 2.5 mM AgNPs , 7.0 pH , 40 ˚C for 1.5 h. incubation period . Also, the bacterial isolate MAM-S18 has the ability to produce AgNPs extracellularly . The results revealed that the maximum AgNPs production were recorded at 3.0 mM AgNO3 , 8.0 pH , 40 ˚C for 1.5 h. incubation period . Biosynthesized AgNPs of MAM-S17 and MAM-S18 were characterized by UV/VIS spectroscopy , XRD, TEM , FTIR, EDX and DLS. λmax for AgNPs were 420 and 430 nm for bacterial isolates MAM-S17 and MAM-S18 respectively. XRD data indicated the presence of six peaks at 27.63 , 31.99 , 37.96, 44.16 , 64.43 and 76.99 of 2ϴ for MAM-S17 and six peaks at 28 , 31.6, 38.11, 44.17, 64.86, 77.89 of 2ϴ for MAM-S18 . Both AgNPs were spherical and ranging from 1-10 nm with average of 4.37 nm for MAM-S17 and 8.3 nm for MAM-S18. FTIR data indicated differences in region 400 to 1600 cm-1. A peak has been recorded at 1400 cm-1 for MAM-S17 .EDX data indicated a peak of silver metal for both of MAM-S17 and MAM-S18. Immobilization of different concentrations of AgNPs of MAM-S17 against nine clinical bacterial strains four different matrices (filter paper , guaze , cotton , agar ) were investigated. . These clinical bacterial strains were Salmonella sp. MAM-1, Salmonella enteritidis MAM-2, Citrobacter sp. MAM-3, Pseudomonas fluorescens MAM-4, Pseudomonas sp. MAM-5, Staph. aureus MAM-6 , Staph. epidermidis MAM-7, Bacillus subtilis MAM-8 and E. coli MAM-9. These clinical bacterial strains were multidrug resistant bacteria (MDR). AgNps immobilized on cotton fabric sheet discs showed the highest inhibition zone diameter 28 and 25 mm against the two Gram –ve (MDR) strains of Pseudomonas sp. MAM-5 and Pseudomonas fluorescence MAM-4 respectively. However, the other Gram +ve MDR clinical bacterial strains , Staph aureus MAM-6 and Staph epidermidis MAM-7 showed inhibition zone diameter (24 mm) . The most efficient matrix was cotton sheet followed by filter paper even at low concentration especially against Pseudomonas spp. and Staphylococcus spp. However, the only effective matrix and dose against E. coli was cotton at the highest concentration . The worst matrix was agar discs . Sterilization of AgNPs immobilized on cotton fabric sheet have been recorded at 10 and 25 KGY of gamma radiation.