| Summary: | 碩士 === 國立東華大學 === 海洋生物科技研究所 === 99 === The marine ecosystem provides a unique environment for diverse microorganisms to produce metabolites with different biological activities. In this research, seven marine and five mangrove sediment samples were collected from ten different locations in southern, eastern, and southwestern Taiwan. They were used to screen for antimicrobial activity produced by actinomycetes and fungi. Actinomycetal and fungal strains were first isolated with six actinomycetal selective medium and two fungi selective medium by agar-based culture method. A total of 1709 bacterial and 365 fungal strains were isolated from the sediment samples. Among them, 15 actinomycetes and seven fungi showed antimicrobial activity. The 16S and 18S rDNA fragments of these actinomycetes and fungi, respectively, were amplified by polymerase chain reaction and their DNA sequences were compared with GenBank database. Phylogenetic analysis of these sequences indicated that the actinomycetal strains belong to two genera: Streptomyces (14 strains) and Nocardiopsis (1 strain). The seven fungal strains belong to three genera: Trichoderma (3 strains), Aspergillus (2 strains), and Fusarium (2 strains). In addition, ten actinomycetes (66.7%) and three fungi (42.87%), thirteen actinomycetes (86.71%) and six fungi (85.74%), as well as ten actinomycetes (66.7%) and two fungi (28.57%) were found to have anti-inflammatory activity, cytotoxicity activity, and biological toxicity activity, respectively, using crude extracts from fermentation broth. Actinomycete LY-A-44, which had the strongest antimicrobial activity against most of the pathogens tested, was selected for further studies. The optimal growth condition for LY-A-44 was at 30oC, 150 rpm with 0.2% glucose, 0.4% peptone, and 0.4% yeast extract, and the antimicrobial activity was the strongest after three days of cultivation. Our study demonstrates that the culturable actinomycetes and fungi from marine and mangrove sediments have great potential in discovery of new medically relevant compounds.
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