The production of ‘Bakasang’, an Indonesian fermented fish sauce, was replicated in the laboratory in order to study the physicochemical and microbiological changes associated with the process. Bakasang samples were produced by incubating mixtures of small sardine (Engraulis japonicus) at different concentrations of sodium chloride and glucose at 37°C for 40 days. Changes in pH, total soluble nitrogen, total free amino nitrogen, amino acid composition and total plate counts were observed. The isolation and identification of microflora were also performed. In general, the pH decreased throughout the incubation period, irrespective of NaCl and glucose concentrations. Increases in the amounts of total soluble nitrogen and total free amino nitrogen were noticed during the 40 days of fermentation. The amino acids, glutamic acid, alanine, isoleucine, and lysine were prominent at the end of the process. The total plate count increased during the first 10 days and then decreased gradually for both total microbial population and lactic acid bacteria population.Micrococcus,StreptococcusandPediococcusspp were predominantly present during Bakasang fermentation.

Indonesia is famous for its underwater biodiversity, which attracts many tourists, especially divers. This is also true for Sangihe Islands Regency, an area composed of several islands in the northern part of North Sulawesi. However, Sangihe Islands Regency is much less known than, e.g., Bunaken National Park (BNP, North Sulawesi). The main island, Sangihe, has recently experienced an increase in tourism and mining activities with potentially high impact on the environment. Recently, monitoring projects began around BNP using marine Heterobranchia as indicators for coral reef health. No information about this taxon exists from the remote islands in North Sulawesi. The present study represents the first monitoring study ever and focuses on marine Heterobranchia around Sangihe. In total, 250 specimens were collected, which could be assigned to Sacoglossa (3), Anthobranchia (19), and Cladobranchia (1). Despite the low number (23 versus 172 in BNP), at least eight species (35%) are not recorded from BNP, probably indicating differences in habitat, but also influence of a strong El Niño year in 2016. Here we also report for the first time a Chromodoris annae specimen mimicking C. elisabethina, and the discovery of a new Phyllidia species.

Abstract. Balansa W, Wodi SIM, Rieuwpassa FJ, Ijong FG. 2020. Agelasines B, D and antimicrobial extract of Agelas sp. from Tahuna Bay, Sangihe Islands, Indonesia. Biodiversitas 21: 699-706. The alarming growth of antibiotic-resistant bacteria necessitates the discovery of new antibiotics including those for combating life-threatening ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp) and fish pathogenic bacteria. This study aimed to identify antimicrobial compounds from an extract of a marine sponge collected from Enepahembang coral reef, Sangihe Islands, North Sulawesi, Indonesia. The sponge was identified by DNA barcoding as Agelas sp. and its extract was evaluated against three ESKAPE bacteria (S. aureus, K. pneumoniae, and A. baumannii) and three fish pathogenic bacteria (A. hydrophila, Edwardsiella tarda and Vibrio parahaemolyticus), using the standard disk diffusion method. It showed moderate to strong antimicrobial activity against S. aureus (25.3 mm), K. pneumoniae (15.5 mm), A. baumannii (20.2 mm), A. hydrophila (20.5 mm), E. tarda (22.4 mm) and A. salmonicida (21.2 mm). The extract was isolated by chromatographic techniques (column chromatography, flash chromatography, and high-performance liquid chromatography). The structures and relative stereochemistry of the two compounds were elucidated by HRESIMS, 1D and 2D NMR data analysis as well as by comparison with reported values. Unfortunately, limited amount of the pure compounds prevented us from further evaluating their antimicrobial activity against the test bacteria. Nevertheless, the crude extract's strong antimicrobial activity, especially against the test Gram-negative bacteria, suggests the importance of this finding in light of the recent antimicrobial drug scarcity but rapid antimicrobial resistance and the emerging paradigm of antimicrobial drug modification, redirection and/or repurposing for discovering new antibiotics particularly against the life-threatening Gram-negative bacteria.

Sponges are a well-known bioresource for bioactive compounds. In this study, antibacterial activity-guided fractionation of the extract from an Indonesian marine Dactylospongia elegans sponge led to the discovery of four merosesquiterpenoids, namely, a new sesquiterpenoid aminoquinone nakijiquinone V (1), along with illimaquinone (2), smenospongine (3), and dyctioceratine C (4). The structure of compound 1 was elucidated by 1D and 2D NMR as well as by LC-HRESIMS data analysis. Compounds 2–4 showed moderate to low antimicrobial activity against Bacillus megaterium DSM32 with a minimum inhibitory concentration (MIC) of 32 μg/mL, 32 μg/mL, and 64 μg/mL, respectively. Furthermore, compounds 2 and 3 both inhibited Micrococcus luteus ATCC 4698 with a MIC of 32 μg/mL. In conclusion, the isolated merosesquiterpenoids, which are known for their cytotoxic effects, showed antibacterial activity and prompt future structure activity relationship (SAR) studies concerning the various bioactivities observed for this group of natural products.

The potential of sponge-associated bacteria for the biosynthesis of natural products with antibacterial activity was evaluated. In a preliminary screening 108 of 835 axenic isolates showed antibacterial activity. Active isolates were identified by 16S rRNA gene sequencing and selection of the most promising strains was done in a championship like approach, which can be done in every lab and field station without expensive equipment. In a competition assay, strains that inhibited most of the other strains were selected. In a second round, the strongest competitors from each host sponge competed against each other. To rule out that the best competitors selected in that way represent similar strains with the same metabolic profile, BOX PCR experiments were performed, and extracts of these strains were analysed using metabolic fingerprinting. This proved that the strains are different and have various metabolic profiles, even though belonging to the same genus, i.e. Bacillus. Furthermore, it was shown that co-culture experiments triggered the production of compounds with antibiotic activity, i.e. surfactins and macrolactin A. Since many members of the genus Bacillus possess the genetic equipment for the biosynthesis of these compounds, a potential synergism was analysed, showing synergistic effects between C14-surfactin and macrolactin A against methicillin-resistant Staphylococcus aureus (MRSA).