Screening of antibacterial activity in marine green, red and brown macroalgae from the western coast of

Marine macroalgae are considered as an excel-lent source of bioactive compounds which has a broad range of biological activities including antibacterial and antioxidant. Crude methanolic and water extracts of 19 marine algal species (6 Chlorophyta, 8 Phaeophyta and 5 Rhodophyta) collected from the western coast of Libya were evaluated for antibacterial activity against patho-genic bacteria (4 Gram-positive, 4 Gram-nega-tive). The extracts showed a significant antibac-terial activity against Gram positive (Staphylo-coccus aureus, Bacillus subtilis, Bacillus spp., and Staphylococcus epidermidis) as well as Gram negative bacteria (Escherichia coli, Salmonella typhi, Klebsiella spp., and Pseudomonas aerugi-nosa). The algal aqueous and methanolic ex-tracts displayed different degrees of antimicro-bial activities against different bacteria, in some cases methanolic extracts showed higher anti-bacterial activity than aqueous extracts. Among tested algae, Brown algae namely Cystoseira crinite exhibited the highest antibacterial activity among tested algal species