الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Nanomaterials have unique and new functions due to the size effect phenomenon. Increasing of surface to volume ratio leads to increase in function and reactivity of surface atoms .Processes used for nanoparticles synthesis are chemical, physical, and a recently developed biological method. The chemical method uses chemical stabilizers that lead to environmental pollution. In contrast, biological synthesis of nanoparticles is superior due to a clean, cost effective, easy to operate and non–toxic approach which produces nanoparticles with novel properties. In the field of biological synthesis of nanoparticles, microorganisms are of great importance in this respect. Bacteria have been more focused due to their high resistance to metals and surviving under harsh environment. Among nanoparticles, metallic and metalloid nanoparticles have been widely considered because of their catalytic, photo catalytic, absorbent, optical, electrical and magnetic applications. Biosynthesis of selenium and silver nanoparticles are two examples. Thus, the objectives of the present study were ; green synthesis of selenium and silver nanoparticles using aquatic bacteria, characterization of NPs by use of UV–Vis spectrophotometry, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy, energy dispersive X-ray (EDX) analysis, and development of biogenic nanocomposites for environmental applications. Selenium nanoparticles (Se-NPs) have gently stimulated more extensive interest due to their vital properties. During this intensive investigation, we tend to use aquatic bacteria isolated from Qarun Lake for the green synthesis of nano selenium and its potential applications as antimicrobial, accomplished by removal of toxic mercury from required water. In this study, twenty-four distinctive bacterial isolates were purified and screened for selenite resistance, and ten were positive. Out of the ten isolates, Q5 and Bats 2 had been excellently proved tolerant to sodium selenite with minimal inhibitory concentrations (MIC) 8 and18 g/L, respectively. These isolates have continually been the best isolates in the manufacture of Se-NPS with maximal coloration and absorbance at 420 nm, in three days of growth at pH 7 and 35 C°, and with 1g/l sodium selenite. The best extracellular biomanufacturing of Se-NPs isolates have been properly identified using morphological, biochemical and 16S rRNA gene sequence as Bacillus subtilis and Enterobacter cloacae. The facile fabricated Se-NPs by the most powerful isolate Bacillus subtilis have been consistently characterized using numerous analytical methods as well as UV visible spectroscopy, XRD, SEM, and TEM. The doubtless generation of selenium nanoparticles was established from the distinctive look of red change by the culture broth and broad absorption peaks within the UV vis. Biosynthesized nanoparticles had to represent the spherical form, with a mean diameter of 31-193 nm using TEM. Typical XRD patterns sufficiently established the imprecise nature of the fabricated nanoparticles. Also, in this study in order to clarify how the nanoselenium synthesized by the isolated bacteria, the protein pattern of the bacterial cultures was analyzed. The results proved the synthesis of new proteins induced by selenium ions, compared with the selenium free cultures that increased selenium nanoparticles biosynthesis. The picture of protein pattern produced by SDS-PAGE electrophoreses revealed that the capping proteins as well as peroxidase enzyme were detected. The peroxidase enzyme was recorded in all treatments with molecular weight about 36 kDa. Also, capping proteins were detected as attached proteins with biosynthesized selenium nanoparticles at molecular weight of 25, 41 and 60 kDa. The significant impact of Se-NPs was fastidiously observed on the potential growth of pathogenic Gram-positive and Gram-negative bacteria. Our desired outcomes absolutely confirmed the antimicrobial activity of Se-NPs only against Staphylococcus aureus. Moreover, it, s satisfactorily proved that the cheap bionanocomposite sponge prepared through growing Se-NPs on the surface and throughout the majority of a polyurethane sponge exhibited a smart elimination rate of mercury ion (Hg2+) from mercury-contaminated water. Thus, bacterial Se-NPs composite might realize appropriate application as a bioremediation tool of toxic mercury in required water. Also, among the metal nanoparticles, silver nanoparticles (AgNPs) have received much attention in various fields, such as antimicrobial activity, therapeutics, water treatment and bio-molecular detection. In such a situation, screening of unexplored microorganisms for AgNPs synthesizing property is very important. In the present study, out of 20 morphologically different isolates were obtained from the collected water samples from different eight locations at Rosetta branch of Nile Delta, Egypt. Only six bacterial isolates had the ability to produce brown color of AgNPs. The results cleared that the most efficient bacterial isolates (R3) produced the highest amounts of AgNPs after 24h incubation period, with maximal coloration and absorbance at 420 nm, pH 7, 20 C° and mixing 0.2% AgNO3 with the culture supernatant. The strongest extracellular biomanufacturing AgNPs isolates has been properly identified using morphological, biochemical and 16S rRNA gene sequence as Bacillus tequilensis. The silver nanoparticles produced by Bacillus tequilensis isolate have been consistently characterized using numerous analytical methods as well as UV visible spectroscopy, SEM and TEM. The biosynthesized nanoparticles represented the spherical form, with a mean diameter of 2.74 to 28.4 nm, using TEM. In this study, the antimicrobial activity of silver nanoparticles at different concentrations was monitored against some pathogenic microbes. The results indicated that the synthesized AgNPs had a high antimicrobial activity against all the tested microbes. The highest inhibition zone of 21mm diameter was observed against L. monocytogenes ATCC- 35152 and the lowest of 9 mm was noted against Sal. Typhi ATCC 15566. Also, the stabilized prepared AgNPs-SA nanocomposite has greater catalytic activity for the decolorizing some dyes such as methylene blue (MB) and Crystal violet.