Abstract
The cyclic peptides portoamides produced by the cyanobacterium Phormidium sp. LEGE 05292 were previously isolated and their ability to condition microcommunities by allelopathic effect was described. These interesting bioactive properties are, however, still underexplored as their biotechnological applications may be vast. This study aims to investigate the antifouling potential of portoamides, given that a challenge in the search for new environmentally friendly antifouling products is to find non-toxic natural alternatives with the ability to prevent colonization of different biofouling species, from bacteria to macroinvertebrates. A multi-bioassay approach was applied to assess portoamides antifouling properties, marine ecotoxicity and molecular mode of action. Results showed high effectiveness in the prevention of mussel larvae settlement (EC50 = 3.16 µM), and also bioactivity towards growth and biofilm disruption of marine biofouling bacterial strains, while not showing toxicity towards both target and non-target species. Antifouling molecular targets in mussel larvae include energy metabolism modifications (failure in proton-transporting ATPases activity), structural alterations of the gills and protein and gene regulatory mechanisms. Overall, portoamides reveal a broad-spectrum bioactivity towards diverse biofouling species, including a non-toxic and reversible effect towards mussel larvae, showing potential to be incorporated as an active ingredient in antifouling coatings.
Highlights
As soon as a surface is immersed in water, it is rapidly colonized by a wide diversity of organisms in different developmental stages in a process known as marine biofouling [1,2]
EC50 (
Considering pure compounds isolated from cyanobacterial strains and tested for antisettlement activity, portoamides are more effective than hantupeptin C (EC50 = 10.6 μg·mL−1 ), but less potent than isomalyngamide A (EC50 = 2.6 μg·mL−1 ), majusculamide A (EC50 = 0.54 μg·mL−1 ), and dolastatin 16 (EC50 = 0.003 μg·mL−1 ), all isolated from the cyanobacterium Lyngbya majuscula [32]
Summary
As soon as a surface is immersed in water, it is rapidly colonized by a wide diversity of organisms in different developmental stages in a process known as marine biofouling [1,2]. The surface adhesion of organic molecules takes place, followed by the rapid settlement of microorganisms like marine bacteria, protozoans and microalgae [3]. These microfouling communities develop into complex marine biofilms, which provide favourable conditions in which spores of macroalgae and larvae of invertebrates can establish themselves, leading to the attachment of these macrofouling. Marine fouling results in an increase of fuel consumption of ships and represents a major vehicle for the spread of invasive marine species [8,9] Macrofouling organisms such as invertebrates and algae are responsible for a significant percentage of marine fouling biomass and for the diminished hydrodynamic performance of a ship [10]. Marine biofilms that attach to artificial surfaces are recognized to be a significant issue for a wide range of submerged engineered structures and are known to have a significant role in the corrosion of surfaces immersed in seawater [11]
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