Innovative approaches for the development of new non-toxic antifouling solutions
Student thesis: Doctoral Thesis
Marine biofouling can be defined as the undesirable adhesion to surfaces and further growth of organisms, mainly biofilm-forming microbes, macroalgae and invertebrates. The aim of this project was the prevention of adhesion and growth of organisms by using anti-biofilm molecules of natural origin. The antifouling properties of molecules isolated from an Artic marine sponge Stryphnus fortis, a sub-Artic ascidian Synoicum pulmonaria and micropeptides derived from the innate defence protein lactoferrin were assessed.
The bromotyrosine derivative ianthelline isolated from S.fortis is shown to inhibit both marine micro- and macrofoulers with a pronounced effect on marine bacteria (MIC values: 0.1–10 μg/mL) and barnacle larval settlement (IC50=3.0 μg/mL). Four molecules belonging to the recently discovered synoxazolidinone and pulmonarin families-both isolated from S.pulmonaria and four simplified synthetic analogs displayed minimum inhibition concentration (MIC) values in the micro- to nanomolar range against 16 relevant marine species involved in both the micro- and macrofouling processes. Synoxazolidinone C displayed selected antifouling properties comparable to the commercial antifouling product SEA-NINE. Among the 13 micropeptides derived from the innate defence protein lactoferrin, two peptides were particularly active against the microfoulers with MIC-values ranging from 1-0.01 μg/mL and comparable to the antifouling activities of the commercial biocide SEA-NINE.The contamination of tropical marine environments (water column and sediment) by leachate from antifouling paints has led to concern regarding the effects on corals and their symbionts. Therefore, it is of high importance to evaluate the impact of antifouling compounds on key coral reef organisms. The potential toxicity of two commercial biocides (SEA-NINE and Irgarol), one synthetic biocide (thiram) and two biocides of natural origin (myristic acid and Totarol) were assessed at environmental concentrations, toward the survival of two species of Symbiodinum sp.: Symbiodinium microadriaticum and Symbiodinium voratum. SEA-NINE-and Irgarol affect the growth and survival rate of the two species of symbiont but myristic acid, thiram and Totarol have shown no long term effect on Symbiodinium spp. Application of thermal stress (+2°C) increased the toxicity of SEA-NINE-and Irgarol to these species. The effect of increased mortality of these symbionts on coral bleaching as sea temperatures rise is unclear
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