Isolation, identification and analysis of antibacterial activity of soil streptomycetes isolates from north Jordan

A total of 90 different Streptomyces isolates were recovered from 36 soil samples and assessed for their antibacterial activity. Nine isolates were identified by the absence of an aerial mycelium. The rest were grouped into six colour series, namely grey, white, yellow, green, red and polymorphic colours (pink, orange or violet) with total numbers of 29, 18, 14, 8, 3 and 9, respectively. The isolates (68%) showed a reverse side culture pigmentation, 30% produced melanin and 25% produced other soluble pigments. Isolates (48%) were characterized by flexuous spore chains, 21% with spiral and 10% for each of the rectus and retinaculum apertum arrangement. The antibiotic activity against a wide range of bacteria was exhibited by 54% of the isolates which were effective against Bacillus subtilis (57%), Staphylococcus aureus (47%), Escherichia coli (24%), Klebsiella spp (16%), and Shigella spp (12%). The lowest activity (8%) was exhibited against Pseudomonas spp and Salmonella spp. The antibacterial activity of the isolates was divided into four groups according to the diameter of the inhibition zone produced. Groups 3 and 4 with larger inhibition zones indicated their potential as a possible source of novel antibiotics.