Antimicrobial and antifouling activities achieved by extracts of seaweeds from Gulf of California, Mexico

Six species of common seaweed extracts were tested in laboratory assays: Dictyota flabellata, Padina concrescens, Laurencia johnstonii, Gymnogongrus martinensis, Ulva lactuca and Codium fragile for potential industrial applications through evaluation of the antibacterial activity against pathogenic bacteria (5 strains) and the antifouling potency against the growth of key species of marine colonisers (7 bacteria, 5 fungi and 11 microalgae). The organic extract of L. johnstonii, U. lactuca and D. flabellata have bacterial antibiosis. The ethereal extracts were more active in comparison with buthanol extracts against the bacterial strain Staphylococcus aureus. The best antifouling results were obtained with U. lactuca and L johnstonii (0.1-1 μg ml^-1) againstall strains tested. C.fragile exhibited significant antifouling activity with minimum inhibitory concentration (MIC) between 1-10 μg ml^-1 against marine microalgae Rhodosorus magnei, Neorhodella cyanea and Prymnesium calathiferum.