Antibacterial activity of macroalgae crude extracts from Paraná coastal islands (Brazil) against marine isolate of Enterobacteriaceae (Atena Editora)

Abstract

Coastal organic pollution results in eutrophication and distributional changes of microorganisms. Besides, flow of commercial antibiotics through the domestic effluents favors bacterial resistance, demanding new drugs and bioremediation processes. Macroalgae protective responses are attributed to their secondary metabolites, reason why is widely studied for bioactivities. We investigated the antibacterial activity (AA) of methanolic and aqueous extracts of four macroalgae species from Paraná coastal islands, being: Pyropia acanthophora (Rhodophyta), Sargassum cymosum (Phaeophyceae), Ulva sp., and Gayralia brasiliensis (Ulvophyceae) from Paraná coastal islands, Brazil. The crude extracts were tested against an environmental Enterobacteriaceae isolated and cultivated from a eutrophic estuary, and compared to the reference strain, E. coli ATCC 25922. The environmental strains from Paranaguá Bay sample water were isolated using Colilert®T18 and filter membrane. Gram stain and biochemical tests were performed to confirm the Enterobacteriaceae. The extract yields were calculated and related to antibacterial activities, evaluated by disk diffusion and broth microdilution. The investigated species showed AA only for methanolic extracts. Ulva and S. cymosum showed higher extracts yields. Ulva sp. inhibited E. coli activity in ca. of 70%, for both strains and all concentrations tested. P. acanthophora showed the higher inhibition value, however only at higher extract concentration and presenting the lower extract yields. S. cymosum extracts inhibited both strains in 70 - 80%, at higher concentration tested. Besides other studies revealed bioactivities for G. brasiliensis, our only species collected in a conservation unity area, their extracts showed low AA and yields in the tested conditions. Considering Ulva and Sargassum broad global distribution, and high biomasses, these are our best candidates for AA. Further molecular tests of the environmental isolate and biochemical characterization of the antibacterial compound(s) are highly recommended, aiming to explore new sustainable applications of these extracts with AA for marine biotechnological processes, products or endeavors, related to human health or marine conservation.