Growth Phases of Some Antibiotics Producing Streptomyces and their Identification

The growth phases of five cultures of antibiotic producing Streptomyces isolated from western region, Saudi Arabia were studied spe- . cial reference to their potentiality to excrete antibiotics. It was found that these organisms grew exponentially during the first 4 to 7 days of incuba- tion. The highest specific growth rate was observed in the case of Strep- tomyces MY18 being 0.48 day-l (1.44 days doubling time). This isolate also showed the highest inhibition zone against Staph. aureus as compared with the other four Streptomyces isolates. This antagonistic effect was more pro- nounced at the last five d~ys of incubation (stationary phase). Morphologi- cal, cultural and physiological properties of most active antibiotic producers revealed that Streptomyces MY18 and Streptomyces MR13 are strains of S. aureofaciens and S. reseviolaceus respectively.