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King Abdulaziz University (2020)

Extreme Habitats of Saudi Arabia as Sources of Novel Actinomycetes with Antimicrobial Activities

Bahamdain, Lina Ahmed

Titre : Extreme Habitats of Saudi Arabia as Sources of Novel Actinomycetes with Antimicrobial Activities

Auteur : Bahamdain, Lina Ahmed

Université de soutenance : King Abdulaziz University

Grade : Doctoral Thesis 2020

Résumé partiel
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

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Page publiée le 14 décembre 2022