Forty-nine Streptomyces isolates were recovered from sediment samples in the gulf of Aqaba/Jordan. All isolates were tested for antimicrobial activity against Gram positive bacteria, Gram negative bacteria, and yeast. Twenty eight Streptomyces isolates were active against at least one of the tested strains. The majority of the isolates showed activity against Gram positive bacteria: Streptomyces aureus (89%), Streptomyces epidermidis (64%) and Bacillus Subtilis (50 %). Lower activity was observed toward Gram negative bacteria with only 25% active against Pseudomonas aeruginosa, whereas only 17% were active against the yeast Candida albicans. Isolate S34 showed best activity. It produced heat stable antimicrobial activity at both acidic and alkaline pH (5 to 5.5 and 8 to 9.5). S34 was found to be related to Streptomyces rochei. Forty-nine Streptomyces isolates were screened for genes encoding non ribosomal peptide synthetases (NRPS) and polyketides synthases (PKS; types I and II). NRPS sequences were widely distributed and detected in 81% of Streptomyces isolates. PKS types I and II were detected in 63.2 and 65.3% of isolates, respectively. Additionally, the relationship between the occurrences of biosynthetic gene sequences (NPRS and PKS sequences) and the production of antimicrobial activities was determined. The above results reveal that the marine Streptomycetes are a promising source of novel and unique products.
Key words: Marine Streptomyces, antimicrobial activity, non ribosomal peptide synthetases (NRPS), polyketides synthases (PKS), enzymes, gulf of Aqaba, Jordan.
Abbreviations: NRPS, Non ribosomal peptide synthetases; PKS, polyketides synthases; A, Adenylation; T, thiolation; C, condensation; ISP, international Streptomyces project.
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