Judul: Antimicrobial Activity of Sponge-Haliclona sp.-Associated Bacteria and Their Genetics Analysis
Abstrak: Three marine bacterial isolates isolated from sponge-Haliclona sp. coded as HAL-13, HAL-74, and HAA-01 produced broad spectrum of antimicrobial compounds. Extraction of antimicrobial compounds has been performed using n-butanol and ethyl acetate solvent. Bacterial crude extracts from all of these isolates showed broad spectrum activity against bacterial and fungal test strains, i.e. Staphylococcus aureus, Pseudomonas aeroginosa, enteropathogenic Escherichia coli K1-1, Candida albicans, and Candida tropicalis. Crude extract from HAL-13 showed the highest antimicrobial activity against bacterial and fungal test strain. Analysis of active spot from thin layer chromatography plate was conducted by bioautography technique. At least one spot from each bacterial crude extract has antimicrobial activity against Staphylococcus aureus and enteropathogenic Escherichia coli K1-1. Purification of antimicrobial compounds from HAL-13 were performed using column chromatography with chloroform-methanol solvent system. Thirty-seven fractions were collected from column chromatography, five fractions of which have antimicrobial activity. DNA fragment of ketosynthase of polyketide synthase genes cluster from HAL-13, HAL-74, HAA-01 were amplified and successfully cloned into pGEMT-Easy. Sequences analysis showed that they had homology with PKS type of 1 B. subtilis BSN5 for HAL 13 and HAA-01, and PKS type 1 of B. amyloliquefaciens for HAL-74.
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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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