Judul: Sponge-associated Bacteria Producing Antimicrobial Compounds and their Genetic Diversity Analysis
Abstrak: Bacteria associated with the marine sponge Haliclona sp. from the coastal region of Waigeo Island were screened for antimicrobial activities using the agar-overlay method. There were 125 bacterial isolates recovered and were subjected to antimicrobial screening for antibiotic production against five test bacterial strains, viz., Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Enteropathogenic Escherichia coli (EPEC), Pseudomonas aeruginosa and two fungal pathogen, viz., Candida albicans and Candida tropicalis. A total of 39 (31%) bacterial strains were found to be antimicrobial producers; however, 15 (38%) of these active strains were eliminated based on the results of Hemolytic Test. The remaining 24 isolates were further analyzed by amplified ribosomal DNA restriction analysis (ARDRA) to assess their genetic diversity and results obtained revealed eight phylotypes. There were nine isolates that were exhibiting wide spectrum of activities against the test strain. The Minimum Inhibitory Concentration of the nine strains was determined and three strains (HAL13, HAL74, and HAA01) showed bactericidal effects. Bacterial extracts were obtained using n-butanol and were subjected to bioactivity assay and TLC autobiography overlay assay. Phylogenetic analysis using 16S rRNA gene sequences revealed that the nine strains belong to the genus Bacillus. The isolation of sponge associated bacteria possessing inhibitory activity against clinical pathogenic strains suggests that they could be potential sources of novel marine natural products.
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Judul: Analysis of bioactive compounds as wide Spectrum antimiccrobial from sponge associated bacteria from Haliclona sp.
Abstrak: Senyawa antimikrob berspektrum luas dari enam isolat yang berasosiasi dengan spons Haliclona sp. diekstrak menggunakan pelarut etil asetat. Keenam isolat tersebut adalah HAA-02, HAA-07, HAL-08, HAL-10, HAL-20, dan HAL-23. Ekstrak kasar bakteri tersebut kemudian diuji aktivitasnya terhadap beberapa mikrob patogen dan non patogen. Hasilnya sebagian ekstrak kasar isolat bakteri marin tersebut memiliki aktivitas hambatan terhadap S. aureus, EPEC, B. subtilis, E. coli, P. aeruginosa, dan C. albicans. Konsentrasi hambatan minimum (MIC) dari supernatan bakteri marin tersebut berkisar antara 12,5% hingga 100%. Hasil kromatografi lapis tipis dibawah sinar UV 365 nm menunjukkan bahwa masing-masing isolat bakteri marin memiliki fraksi yang aktif menghambat P. aeruginosa melalui uji bioautografi. Dua dari enam isolat membawa gen poliketida synthase (PKS) dan lima dari enam isolat membawa gen nonribosomal peptide syntethase (NRPS).
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. Suatu graf lengkap berorder 𝑛������ ≥ 3 dan graf r-regular berorder 𝑛������ ≤ 2𝑟������ + 1 merupakan graf Hamilton, Karena kedua graf tersebut memuat cycle Hamilton. Selanjutnya, syarat cukup tersebut digunakan untuk menentukan keberadaan cycle Hamilton pada graf 2-connected 4- regular berorder kurang dari 10.
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular