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Horseshoe crabs have survived for a long period due to their myriad defence mechanism. Thorough studies were conducted on their adaptive defence mechanisms but few highlighted their primary innate defence. This study aimed to determine the antifouling properties of the methanolic crude extracts and fractions obtained from the book gills and carapace of the Tachypleus gigas and to characterize their bioactive metabolites, using the detachment and preventive measurements. The active fractions recovered from the recycling HPLC were further analysed using GC-MS and major active constituents were identified. The results obtained indicated that the extract and fractions of T. gigas had significant detachment mode of actions for antifouling activities. Chemical interactions such as synergistic effects were observed in both the book gills and the carapace. Chemical profiles indicated the presence of organic acids such as amino acid, simple sugars and fatty acids. The observed activities might be caused by nutrient-induced biofilm dispersion mechanisms. These findings may provide new insight into the defence mechanism of the horseshoe crabs against biofilm formation. The isolated active fractions and the identified molecules from the horseshoe crab T. gigas may be applied as a dispersal antifouling agents. Further studies are needed to confirm these prospective potential applications. [ABSTRACT FROM AUTHOR]

Epigenetic agents, histone deacetylase inhibitor (SAHA) and DNA methyltransferase inhibitor (5-Aza), were added to Czapek-Dox medium to trigger the chemical diversity of marine - derived fungus Aspergillus versicolor XS-20090066. By HPLC and 1H NMR analysis, the diversity of fungal secondary metabolites was significantly increased compared with the control. With the aid of MS/MS-based molecular networking, two new nucleoside derivatives, kipukasins K (1) and L (2) were obtained. Meanwhile, the yields of four known nucleoside derivatives were significantly enhanced. In addition, one new bisabolane sesquiterpene, aspergillusene E (7), along with ten known derivatives were also isolated. The structures were elucidated by comprehensive spectroscopic methods of NMR and HRESIMS analysis. Compounds 1 and 7 displayed antibacterial activities against Staphylococcus epidermidis and Staphylococcus aureus with the MIC values of 8–16 μg/mL. Our study revealed that the fungus A. versicolor XS-20090066 has been effectively induced by chemical epigenetic manipulation with a combination of SAHA and 5-Aza to produce new metabolites. [ABSTRACT FROM AUTHOR]

Members of the marine bacterial genus Pseudoalteromonas have been found in association with living surfaces and are suggested to produce bioactive compounds against settlement of algal spores, invertebrate larvae, bacteria and fungi. To determine the extent by which these antifouling activities and the production of bioactive compounds are distributed amongst the members of the genus Pseudoalteromonas, 10 different Pseudoalteromonas species mostly derived from different host organisms were tested in a broad range of biofouling bioassays. These assays included the settlement of larvae of two ubiquitous invertebrates Hydroides elegans and Balanus amphitrite as well as the settlement of spores of the common fouling algae Ulva lactuca and Polysiphonia sp. The growth of bacteria and fungi, which are the initial fouling organisms on marine surfaces, was also assayed in the presence of each of the 10 Pseudoalteromonas species. It was found that most members of this genus produced a variety of bioactive compounds. The broadest range of inhibitory activities was expressed by Pseudoalteromonas tunicata which inhibited all target fouling organisms. Only two species, Pseudoalteromonas haloplanktis and Pseudoalteromonas nigrifaciens, displayed negligible activity in the bioassays. These were also the only two non-pigmented species tested in this study which indicates a correlation between production of bioactive compounds and expression of pigment. Three members, P. tunicata, Pseudoalteromonas citrea and Pseudoalteromonas rubra, were demonstrated to express autoinhibitory activity. It is suggested that most Pseudoalteromonas species are efficient producers of antifouling agents and that the production of inhibitory compounds by surface associated Pseudoalteromonas species may aid the host against colonisation of its surface. [Copyright &y& Elsevier]