Antibiofilm activity of polysaccharides extracted from marine algae against Pseudomonas aeruginosa and Staphylococcus aureus

The exploitation of macroalgal biomass, as a source of bioactive molecules, could result into the valuable transformation of waste into an economic resource. Water extracts or polysaccharides, from DNA-barcoded macroalgae from Chaetomorpha linum (Chlorophyta) and Agardhiella subulata and Hypnea cornuta (Rhodophyta) collected from the brackish costal Lake of Ganzirri (Italy) were evaluated for the ability to inhibit the biofilm formation by Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213, as biofilm models. The polysaccharides showed dose-dependent inhibitory activity on the biofilms formation. Polysaccharides from A. subulata and C. linum (200 µg/ml) were the most active against P. aeruginosa (41% and 40%, respectively), whereas those from H. cornuta and A. subulata reduced the biofilm formation of S. aureus (24% and 26%, respectively), without affecting bacterial vitality. All the algal extracts (0.05%, w/v with kerosene) possessed high emulsifying activity (up to 70%) with the highest value from C. linum (92%). The ability of C. linum extracts to modify the surface- cell charges and to reduce the cell-wall hydrophobicity of P. aeruginosa and S. aureus could interact with their initial phase of adhesion. Furthermore, A.subulata extract possess the major antiadhesive activity on the S.aureus decreasing its cell wall hydrophobicity as reveled by coating assay. Results based on the surface-coating assay and on the bacterial adhesion to hydrocarbons suggested that algal extracts may act as biosurfactants inhibiting the initial adhesion and disassembling preformed biofilm of P. aeruginosa and S. aureus. These polysaccharides, as noncytotoxic, biodegradable exopolymers with antiadhesive properties, could be useful for novel prospective in medical and nonmedical applications.