الفهرس 
Acknowledgement
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Abstract
The current study was conducted at Sohag University, Faculty of Science in the subject of fungal biodiversity and biotechnology. It was regarded as a pioneering work involving the isolation and identification of fungi from gold mine soils in the Eastern Desert. The obtained results were as follows: 1. In this study, 20 soil samples obtained in April 2016 from the Al-Fawakhir Gold Mine, Red Sea Governorate, Egypt, yielded a total of 240 fungal isolates corresponding to 16 genera and 38 species. 2. On all types of isolation, Aspergillus was the most widespread genus, accounting for 73.6 % of total fungi. It was represented by 18 species, with A. fumigatiaffinis, A. niger, and A. sydowii being the most prominent, accounting for 12.62 %, 11.6 %, and 11.16 % of all fungi, respectively. 3. Fusarium was the runner of Aspergillus comprising 10.65 % of total fungi. It was represented by 3 species namely F. fujikuroi, F. oxysporum and F. solani with F. fujikuroi, F. oxysporum being the prevalent encountering 5.42 % and 5.21 % of total fungi respectively. 4. Chaetomium globosum, Pyrenophora biseptata, Penicillium (3 species), and Talaromyces (2 species) were isolated in moderate incidence. 5. Other fungal species were also recorded in this study but in low incidence as A. alternata, Bisifusarium dimerum, C. lunata, Gymnoascus sp., M. brevicaulis, P. roridum, R. stolonifer, S. strictum, S. racemosum and T. griseum.
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6- Four isolates that were chosen to check their productive capabilities for the synthesis of gold nanoparticles were examined. They are A. terreus, A. ochraceus, A. quadrilineatus and A. fumigatiaffinis 7. The most potent 4 strains were confirmed by sequencing their internal transcribed spacer gene (ITS) and pure cultures of these four isolates were preserved in the Assiut University Mycological Centre (AUMC) culture collection under the accession numbers Aspergillus terreus AUMC 14354, Aspergillus ochraceus AUMC 14355, Aspergillus quadrilineatus AUMC 14356, and Aspergillus fumigatiaffinis AUMC 14357. 8. The current results showed that 0.25 mM of HAuCl4.3H2O solution was the optimal concentration for Au-NPs synthesis by A. terreus and A. ochraceus producing more intense purple colors. On the other hand, 0.125 mM of HAuCl4.3H2O was the best concentration for both A. quadrilineatus and A. fumigatiaffinis. 9. Both A. terreus and A. ochraceus demonstrated high stability with concentrations of 0.25 mM, while A. quadrilineatus and A. fumigatiaffinis gained the highest stability of the synthesized nanoparticles at 0.125 mM of gold ions. 10. The concentration 0.25 mM of HAuCl4.3H2O was the optimal for Au-NPs synthesis by A. terreus at 40 °C and A. ochraceus at 25 °C, while 0.125 mM was the best for both A. quadrilineatus at 25 °C and A. fumigatiaffinis at 40 °C. However, gold nanoparticles synthesized by A. terreus, A. ochraceus, and A. quadrilineatus at 40 °C were more stable and efficient. While 25 ºC was the best degree in terms of stability of gold nanoparticles synthesized by A. fumigatiaffinis.