Extracts of marine algae, sponge and humic acid sediments were tested against different bacterial
pathogens by well-cut agar diffusion method. Chloroform crude extracts were superior to the ethanolic crude
extracts. The brown alga Cytosoria compressa had broad spectrum antimicrobial effect against different
bacterial pathogens. Activity units ranged from 3.1 for S. faecalis to 6.9 for E. coli. Also, chloroform crude
extracts of sponge inhibited the growth of all bacterial pathogens. Extracts of Spongia officinalis (Alam El-
Room at 50m) showed the highest inhibiting activity. Activity units ranged from 4.59 against S.aureus,
S.faecalis and P.aeruginosa to 6.61against E.coli. Humic acid extracted from sediments of the Eastern Harbour
and Abu-Qir inhibited only the Gram-negative bacteria while the humic acid extracted from Mariut Lake had
inhibitory effect only on Staphylococcus aureus The gas liquid chromatography mass spectrometer of
C. compressa and S. officinalis extracts was determined and the main constituents were fatty acids and their
esters (hexadecanoic acid and octadecanoic acid) which have antimicrobial effect.