A total of 125 Streptomyces strains were isolated from an Algerian wetland (Fetzara Lake) and characterized by growth on different culture media. Phylogenetic analyses were carried out by 16S rRNA sequence comparison after PCR amplification using universal primers. Antibacterial bioassays performed by the agar diffusion method enabled us to retain 33 Streptomyces isolates for their activity against two Gram-positive bacteria (Bacillus subtilis and Micrococcus luteus) and one Gram-negative bacteria (Escherichia coli). Among them, six isolates inhibited all three indicator strains. Antibacterial compounds were then extracted from the solid culture media with ethanol and ethyl acetate as organic solvents. The minimal inhibitory concentration (% v/v) of the extracts was evaluated by a standardized broth dilution method against different clinical-resistant bacterial isolates and Candida albicans. The most active crude extracts were selected for further characterization by chromatographic analysis (RP-HPLC).
Keywords: Streptomyces; actinomycetes; antimicrobial activity; diversity; lake water.