This study aimed to determine the antibacterial activity and toxicity of methanol hexane extracts Halymenia durvillei red seaweed which were found abundantly in Kayangan island, South Sulawesi. The crude extract was tested against five gram-negative bacteria, namely Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Aeromonas hydrophila, Vibrio harveyi at a dose 200 g/disk. Extract on ...