Eksplorasi Bakteri Simbion Spons di Ekosistem Lamun

Abstract

Sponge has been acknowledged for its ability to produce secondary metabolites compounds that have been explored for new source of marine natural product compounds. Unfortunately, information on sponge ecological interaction, especially concerning its secondary metabolite production and symbiotic organisms, are usually from observation and experimental researches in coral reefs ecosystem. Meanwhile, not many information has been gathered on sponge community and its ecological interaction in the seagrass ecosystem. Information on sponge community and its ecological interaction in seagrass ecosystem should be explored intensively, for seagrass vegetation could has different environmental condition due to seagrass species characterization that composing the ecosystem. Thus, vegetation characterization of seagrass will influence sponge community and its secondary metabolite, and also its interaction with symbiotic microbial (bacterial). This research wants to figure out several issues concerning sponge community in seagrass ecosystem. These issues are: will sponge species composition and association be different due to condition of seagrass vegetation in the ecosystem; is sponge species in seagrass ecosystem have the same potential concerning its antibacterial activity as in reefs area; how diverse the sponge bacterial symbiont and the potential of its secondary metabolite; and also how the ecological interaction between sponge and its symbiotic bacterial. This research was conducted in several stages. The first stage is field observation at seagrass ecosystem. The next stage was conducted as laboratory activities. Laboratory activities were conducted in several phases. The phase was an assay to test the antibacterial activity of sponges tissues on generally tested bacteria (Escherichia coli and Staphylococcus aureus) and marine bacteria isolates from surrounding water (Al1, Al2, Al3, Al4 and Al5). The aims of this activity were to screen potential sponge that having antibacterial activity, and isolating its symbiotic bacterial. Afterwards, the next phase was an assay to test the antagonistic activity of sponge symbiotic bacterial against marine-biofilm forming bacteria. Symbiotic bacterial with high antagonistic activity then analyzed for its species diversity, using molecular analysis of symbiotic bacterial DNA fingerprinting and identification. Field observation was done in two different seagrass meadow/bed in Pramuka Island, Seribu Islands, near Jakarta Bay, Indonesia, since September 2013 to Mei 2014. Laboratory assays activities were done in Marine Microbiology Laboratory and Marine Biosystematics and Biodiversity, Departement of Marine Science and Technology, Bogor Agricultural University (IPB). Antibacterial assay on sponge tissue was conducted since September 2013 to March 2014, whilst isolation on symbiotic bacterial and secondary metabolites assay were done from December 2013 to November 2015. Molecular analysis on bacterial symbionts diversity and identification were just done ons January to May 2016. Results of this research showed that sponge community in seagrass ecosystem was influenced by the density, morphological form and vegetation architectural of seagrass beds. Sponge will have more species number (higher diversity), with lower abundance in patchy seagrass bed. On the contrary, diversity of sponge will be lower, with higher individual number (abundance) in continuous seagrass bed, regarding higher protection mechanism from predatory activities in continuous bed. Overall, sponge community at both seagrass beds (Site 1 and 2) were dominated by Spirastrella sp. (Sp) and Agelas conifera sponges. Antibacterial assay showed that only 7 of 18 sponge species have low activity against pathogenic bacteria (E. coli and S. aureus) and marine bacteria from surrounding water. This probably caused by a conducive environment condition for sponge growth and less environmental stress that could stimulate sponge antibacterial activity. There were 44 different colonies of bacterial symbionts successfully isolated from 9 species of sponge, with 22 active isolates against potential marine biofilmforming bacteria. The higher number of bacterial symbionts was isolated from Haliclona spp. (Hy), Iotrochota sp. (Io) and Aplysina aerophoba, respectively. The antagonistic activity of those 22 symbiotic bacteria has the similar interaction with all targeting bacteria. It showed that all those 22 isolates of 44 symbiotic bacteria isolates have similar activity and antibiofilm potential. This high antibiofilm activity also promising for the search of biofilm modulator compounds that has important values in medicines. The most promising symbiotic bacteria (Aa3) was came from Aplysina aerophoba sponge, with higher activity (more than 9 mm inhibition zone) against 4 marine biofilm-forming bacteria, respectively. Genomic fingerprinting analysis of symbiotic bacteria was used Rep-PCR method. It showed that symbiotic bacteria from same species of sponge have close genetic relation than bacteria from different species of sponges. Nevertheless, DNA sequencing result showed that there was genomic homologous of several bacterial groups from different sponges. 16sDNA sequencing resultsof 12 symbiotic bacteria isolates showed that those bacteria has genomic homologous with α and γ proteobacteria and firmicutes bacterial groups. Ecologically, symbiotic interaction between bacterial symbionts and sponges is a protection mechanism against marine-biofilm forming bacteria for sponge, that was contributed by the symbiotic bacteria, despite sponge antibacterial activity was very low. It’s related with the activation mechanism of sponge chemical defense that need adequate stimulus, such as space competition and/or predation activity by other organisms.