Judul: Ekstraksi dan Bioaktivitas Senyawa Antimikrob dari Bakteri yang Berasosiasi dengan Spons Jaspis sp.
Abstrak: Many bacteria associated with sponges produced secondary metabolite or bioactive compounds that has been identified as antimicrobial, anti-cancer, anti-fungi, and anti-bacteria. This study aims to extract antimicrobial compound produced by bacteria associated with sponge Jaspis sp and to test its toxicity toward Artemia salina prawn. Six potential isolates of bacteria isolated from sponge Jaspis sp., coded as SAB E-8, SAB E-33, SAB E-35, SAB E-38, SAB E-40, and SAB S-43, were extracted by using ethyl acetate solvent. Bacterial crude extracts of antimicrobial compounds were tested its activity toward pathogenic and non-pathogenic microbes. The results revealed that the crude extracts of bacteria inhibited the growth of E. coli, B. subtilis, EPEC K1-1, Stapylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Candida tropicalis. The minimum inhibitory concentration (MIC) from bacterial supernatants range from 12.5% to 100%. Three best isolate i.e. SAB E-35, SAB E-38, and SAB S-43 were fractionated by using thin layer chromatography (TLC). Results of TLC under UV 365 nm and UV 254 nm showed that each extract had active fraction that inhibited P. aeruginsa and EPEC K1-1 through bioautography test. The six bacterial crude extracts were also tested using brine shrimp lethality test (BSLT) with Artemia salina as test organism to find out the toxicity concentration of the extract. Results showed that each extract had different toxicity measured with LC50 provision. SAB E-38 produced the lowest LC50 value which was 81 mg/L.
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Judul: Characterization of Sponge-Associated Bacteria from Jaspis sp. Producing Wide Spectrum Antimicrobial Compound
Abstrak: Nowadays, symbiosis between bacteria and sponge has been learned nowaday. Sponge-associated bacteria are known producing various secondary metabolites that have antimicrobial activity. This research purposed to know characteristic sponge-associated bacteria as producer of wide spectrum antimicrobial compound. Eight isolates of potential bacteria that have been isolated from Jaspis sp. was extracted use solvent n-butanol. They are SAB E-8, SAB E-32, SAB E-33, SAB E-35, SAB E-37, SAB E-38, SAB E-40, and SAB S-43. Antimicrobial activity screening of sponge-associated bacteria extracts showed that SAB E-35 is a bacteria having widest spectrum antimicrobial activity. SAB E-35 can inhibit indicator microbes, e.g. E. coli, Enteropathogenic E. coli (EPEC), Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans and Candida tropicalis. Minimum inhibitory concentration of this isolate is only 6.25% of filtrates to inhibit some indicator microbe. This isolate also has poliketide sinthase (PKS) and nonribosomal peptide sinthetase (NRPS) gene. Analysis based 16S rRNA sequence of SAB E-35 showed homologous with Providencia vermicola and close relationship with some marine bacteria producing bioactive compound (maximum identity 99%).
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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