الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Microorganisms live in extreme habitats, such as Antarctica, caves, hyper saline and hot springs where the microbial communities very likely possessing specific adaptations to their habitats. Cyanobacterial-bacterial-fungal consortium imbedded in polysaccharide secretions are formed in these habitats as a laminated microbial mat. These mats compose of different fundamental bio-functional classes such as cyanobacteria, an oxygenic photosynthetic bacterium (green sulfur bacteria and violet bacteria), aerobic heterotrophs and anaerobes, sulfate-reducing bacteria (SRB), sulfur oxidizing bacteria and methanogenic archaea. Thriving in harsh environments make extremophiles good candidates for the exploration of bioprocesses and biotechnological applications. The goals of this thesis were studying efficiency of four cyanobacterial mats collected from extreme habitat in western desert; two hypersaline lakes (Zieton and Aghormi) as well as two geothermal springs (Cold and Hot) located at Siwa Oasis in bioremediation of Zn, Cd, and Fe metals, biodegradation of crude oil and their effectiveness as antimicrobial and antioxidant agents.The results indicated that cyanobacterial mats showed excellent affinity for adsorbing and removing Zn+2, Fe+2 and Cd+2 metal ions.All extracts of the four cyanobacterial mats have antibacterial and antifungal activity with varying intensity against all six pathogens; Gram-negative bacterial strains; Salmonella typhi (S. typhi), Aeromonas sp., and Pseudomonas aeruginosa (P. aeruginosa), two gram-positive; Bacillus cereus (B. cereus) and Staphylococcus epidermidis (S. epidermidis) and the fungal, Candida albicans (C. albicans). Notably, the antifungal property of the Siwa lakes and springs was observed against the fungi Candida albicans.Chemical composition of 9 extracts of four different cyanobacterial mats were investigated using GC-MS. A total of 191 chemical compounds were found from all microbial films. Hot spring mat contained the highest number of compounds (109 compounds) followed by Aghormi lake mat (93 compounds). The chemical composition varied between lakes and springs. Also, 14 compounds were not found in the data base and the library of the known compounds revealing their potential novelty.The results indicated that the four extracts have close results but methanolic extract of Aghormi biofilm possessed the highest antioxidant activity, with (60.7375%) of inhibition of DPPH radical followed by Zietone biofilm (57.198%) then biofilm cold spring (55.516%) and finally biofilm hot spring (54.133%). The weathering conditions degraded in average about 32.27% of different aliphatic hydrocarbons. Cyanobacterial mats from hypersaline lakes, Zieton and Aghormi, did not affect the degrading efficiency of weathering factors, whereas cyanobacterial mats from freshwater springs, cold and hot springs substantially increase the degrading efficiency of weathering factors up to means of 50.37% and 64.96%, respectively. The aromatic fraction was degraded by weathering factors alone or in combination with cyanobacterial mats more than the aliphatic one. Weathering conditions were responsible for the degradation of 49.6% of different aromatic hydrocarbons. In contrust with cyanobacterial mats from hypersaline lakes; Zieton and Aghormi, the degrading efficiency of weathering factors did not change, whereas inoculation of cyanobacterial mats originated from freshwater springs, cold and hot springs significantly increase the degrading efficiency of weathering factors up to means of 54.83% and 60.84%, respectively.”