Surface metabolites of the brown alga <i>Taonia atomaria</i> have the ability to regulate epibiosis

<p>This study aimed to improve understanding of the strategies developed by the Mediterranean seaweed <i>Taonia atomaria</i> to chemically control bacterial epibiosis. An experimental protocol was optimized to specifically extract algal surface-associated metabolites by a technique involving dipping in organic solvents whilst the integrity of algal cell membranes was assessed by fluorescent microscopy. This methodology was validated using mass spectrometry-based profiles of algal extracts and analysis of their principal components, which led to the selection of methanol as the extraction solvent with a maximum exposure time of 15 s. Six compounds (<b>A</b>–<b>F</b>) were identified in the resulting surface extracts. Two of these surface-associated compounds (<b>B</b> and <b>C</b>) showed selective anti-adhesion properties against reference bacterial strains isolated from artificial surfaces while remaining inactive against epibiotic bacteria of <i>T. atomaria</i>. Such specificity was not observed for commercial antifouling biocides and other molecules identified in the surface or whole-cell extracts of <i>T. atomaria</i>.</p>