Document Details
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Document Type |
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Thesis |
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Document Title |
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Extreme Habitats of Saudi Arabia as Sources of Novel Actinomycetes with Antimicrobial Activities البيئات المتطرفة في المملكة العربية السعودية كمصادر لأكتينوميسيتات جديدة ذات أنشطة مضادة للميكروبات |
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Subject |
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Faculty of Science |
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Document Language |
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Arabic |
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Abstract |
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Recently, there is an urgent need for new drugs due to the emergence of multidrug- resistant pathogenic microorganisms that cause infectious diseases. Also, the demand for industrial enzymes with novel properties is urgently needed. Isolation and exploitation of actinomycetes from extreme habitats have increased leading to discover of potent bioactive natural compounds and avoid re-isolation of known strains. The present study was aimed to isolate actinomycetes from four different unexplored extreme habitats of Saudi Arabia, arid area, caves, marine, and hot spring environments. A total of 54 actinomycetes were isolated on starch nitrate agar based on their distinct morphological appearance. Out of the total isolates, 22 isolates were obtained from arid area soils, 12 isolates were isolated from caves soils, 7 isolates were obtained from marine samples, and 13 isolates were recovered from hot spring soil and water samples. All isolates were examined and characterized using morphological, physiological, and biochemical characters. The isolates ML52, ML53, and ML54 obtained from marine sediments were resistant to a wide variety of antibiotics. The identification of the isolates was confirmed using 16S rRNA. Sequences analysis of 16S rRNA of all isolates revealed that most of them (90.75%) belonged to the genus Streptomyces spp. It was noticed that Streptomyces mutabilis was the dominant species (16.67%) and was recovered from the four examined extreme habitats. Only one isolate, obtained from arid area, belonged to genus Lentzea, and it was most closely related to the type species of Lentzea albidocapillata (99% similarity). Also, two cave isolates were found to be members of the rare genus Amycolatopsis. Sequencing of 16S rRNA of isolates AL3 and AL7 illustrated that these two isolates were considered as uncultured bacteria. The sequences of the isolates obtained from hot spring region were further studied using some bioinformatics programs. All the selected actinomycete isolates were analyzed for some important enzymes production as well as antibacterial activity. Regarding screening for enzymes activity, all four extreme habitats were considered good sources for actinomycetes that produced keratinase, gelatinase, chitinase and lipase. However, amylase and protease production were relatively showed better in arid area and cave actinomycetes. The antibiotic production was determined by agar plug method using different types of tested bacterial pathogens, Staphylococcus aureus, Methicillin resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Acinetobacter baumannii, Klebsiella oxytoca, and Escherichia coli. The very active isolates were the uncultured isolate AL3 obtained from arid area, Streptomyces CL24 isolated from cave region, and Streptomyces mutabilis ML51 isolated from marine environment where they showed antibacterial activity against all tested Gram-positive bacteria. The isolate AL3 recorded the largest inhibition zone diameters of 11.0±0.5, 13.0±0.5, and 15.5±0.5 mm against S. aureus, MRSA, and E. faecalis, respectively. The crude antibacterial agent of the isolate AL3 was extracted using ethyl acetate and dried under reduced pressure. The obtained extract showed antibacterial activity against E. faecalis using agar well-diffusion method and the active material was purified using TLC-bioautography technique. Marine actinomycetes are considered the promising source for antibiotics discovery as most isolates (71.43%) showed antibacterial activity against at least one of the tested bacteria (S. aureus, MRSA, E. faecalis, or E. coli). Other actinomycetes isolated from caves, arid area, and hot spring ecosystems revealed less antibacterial activity 41.67%, 36.36% and 23.08%, respectively. In conclusion, actinomycetes grown under extreme conditions were clearly produced antibiotics and important enzymes. Thus, such bioprospecting needs to be continued both in the same areas as well as from other unique ecological environments of Saudi Arabia to isolate more actinomycetes with novel bioactive compounds. |
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Supervisor |
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Prof. Dr. Magda Mohamed Aly |
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Thesis Type |
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Doctorate Thesis |
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Publishing Year |
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1441 AH
2020 AD |
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Added Date |
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Saturday, June 20, 2020 |
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Researchers
| لينا أحمد باحمدين | Bahamdain, Lina Ahmed | Researcher | Doctorate | |
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