Caespitella pasceri (BEA 0149; Chlorophyceae) and Euglena sp. (BEA 0937, Euglenophyceae) were cultivated at laboratory scale to test growth, physiological characterization and biotechnological poten- tial. At the stationary phase, biomass was harvested, freeze dried and then extracted to obtain three different fractions in methanol, n-hexane and water, with the objective to determine the presence of compounds with potential antibiotic activity against fish pathogenic bacteria. Assays with Listonella anguillarum and Photobacterium sp. were performed using the disk diffusion method. Inhibition zones were observed for the organic extracts from Caespitella pasceri against both, Listonella anguillarum and Photobacterium sp., while aqueous extracts from this strain did not show any activity. Regard- ing the extracts from Euglena sp., only aqueous and methanolic extracts presented inhibition activity against Photobacterium sp. and no activity against Listonella anguillarum. Results show that both strains, Caspitella pasceri and Euglena sp., might be useful to avoid and/or treat infections caused by fish pathogenic bacteria.

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