Antibacterial and anticancer activity of seaweeds and bacteria associated with their surface

Marine algae and bacteria are an inexhaustible source of chemical compounds that produce a wide variety of biologically active secondary metabolites. Marine bacteria have become an important target for the biotechnology industry because of the large number of bioactive compounds recently discovered from them. The aim of this study was to evaluate the antibacterial and anticancer activities of extracts from the seaweeds Egregia menziesii, Codium fragile, Sargassum muticum, Endarachne binghamiae, Centroceras clavulatum and Laurencia pacifica collected from Todos Santos Bay, Mexico. Organic extracts were obtained from bacteria-free algae and from surface-associated bacteria. Pathogen strains of Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa were used to test antibacterial activity and HCT-116 colon cancer cells for anticancer activity. Thirty-five bacterial strains were isolated from the surface of seaweeds and molecular identified as belonging to the phyla Firmicutes, Proteobacteria and Actinobacteria by 16S rDNA sequencing. The strains Cc51 isolated from Centroceras clavulatum, Sm36 isolated from Sargassum muticum, and Eb46 isolated from Endarachne binghamiae showed anticancer activity, with IC50 values of 6.492, 5.531, and 2.843 mu g ml(-1) respectively. Likewise, the extracts from the seaweed-associated bacteria inhibited the growth of the Gram negative bacterium Proteus mirabilis. The biological activity observed in this study offers opportunities for further chemical analyses, such as the isolation of the active compounds responsible for this activity, in order to contribute to the discovery of new drugs.