Title: Antibacterial effect of extracts from two Icelandic algae (Ascophyllumnodosum and Laminariadigitata)

The in vitro antimicrobial effect of seaweed extracts belonging to Ascophyllumnodosum and Laminariadigitata were tested against some pathogens (Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa and Candidaalbicans). In this study, paper disc diffusion assay, absorbance measurements and growth studies were used to elucidate the effects. The organic solvent extracts of A. nodosum and L. digitata exhibited high eranti bacterial activity than water or enzyme extracts against all the test microorganisms. Higher inhibitory effect of organic solvent extracts was found against Gram-positive bacteria than Gram-negative bacteria. Staphylococcus aureus and methicillinresistant S.aureus (MRSA) were the most sensitive test microorganisms. Acetone extracts of A. nodosum showed the strongest antimicrobial activities. The results of the present study indicate the potential use of Icelandic algal extracts as a source of antimicrobial compounds.