Five marine sponges were collected from six stations from the Levantine Basin in the vicinity of Alexandria city, Egypt (Spongia sp., Cinachyrella sp., Ciocalypta penicillus, Axinella verrucosa, and Plakortis simplex).The antibacterial activities against seven pathogenic bacteria; Aeromonas hydrophila, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC8739, Vibrio damsela, Bacillus cereus, Streptococcus faecalis and Escherichia coli, were done. The results showed that the acetone

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... t the acetone extract of Spongia sp. had a broad spectrum and was the most effective against A. hydrophila (AU= 32.1). It was followed by ethanol extract (AU= 25.5). Ciocalypta penicillus and A. verrucosa showed higher antibacterial activity against E. coli, where AUs were 17.4, 17.4 and 16.0 for ethanol, acetone, and methanol extracts, respectively. All extracts treated by trypsin and boiling, completely lost their bioactivities except in some cases, the bioactivities decreased to low levels. The ethanol extract of C. penicillus lost about 64.4% of AU against E. coli. Also, the methanol extract of A. verrucosa lost about 56.4% of AU against E. coli. The GC-MS patterns confirmed that several substances could be easily affected by proteases and temperature, such as fatty acids and their derivatives. Steroids (digoxigenin) and terpenoids (β-Carotene betulin, astaxanthin, and rhodopsin) were also estimated to be among these extracts.