Judul: Penapisan Bakteri Penghasil Senyawa Antimikrob Asal Spons Laut
Abstrak: Sponges are invertebrate found on coral reef ecosystems. Sponges produce many bioactive compounds as a result of secondary metabolites. The bioactive compounds is produced by microorganisms in the presence of sponges tissue as symbionts. Bioactive compounds are potential to be used in the biomedical and pharmaceutical fields, one of them is antimicrobial. This study aims to screen bacteria from marine sponges of Bira Island, Thousand Islands, DKI Jakarta Province, namely Callyspongia sp. and Petrosia sp. that could potentially produce antimicrobial compounds. The results of isolation using six types of medium showed a total of 147 bacterial isolates were isolated from the sponge type Callyspongia sp. and Petrosia sp. The suitable mediums used to isolate bacteria associated with sponge to obtain various types of bacterial colonies, were medium Nutrient Agar and Zobel Marine Agar. The results of the screening obtained from 26 isolates (13%) could produce antimicrobial compound. Seven isolates (5%) of them were able to inhibit five bacterial targets, i.e. Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Escherichia coli (ATCC 8739), and Enterophatogenic Escherichia coli (EPEC). The isolates were CAL36, CAL42, PTR8, PTR21, PTR40, PTR41 and PTR47. Gram staining performed on 26 bacterial isolates showed all of them belong to the group of gram-negative bacteria. Six isolates among 26 isolates were positive hemolysis derived from the sponge type Callyspongia sp., namely CAL22, CAL24, CAL25, CAL26, CAL34, and CAL49.
Keyword: Bogor Agricultural University (IPB), sponge Petrosia sp., sponge Callyspongia sp, hemolysis, Bira Island, antimicrobial compound

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: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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