The genus Streptomyces is a unique subgroup of actinomycetes bacteria that is well-known as prolific products of many bioactive secondary metabolites as well as antibiotics. Streptomyces globosus (S. globosus) is a bacterium species from the genus of Streptomyces. Objective: This study aimed to optimize the growth conditions required for the maximum antibacterial activity of S. globosus isolated from soil samples in Saudi Arabia. The effect of dark/light, temperature, and pH on the growth and antibacterial effect against E. coli ATCC35218, E. coli ATCC25922, Salmonella sp., P. aeruginosa ATCC27853, S. aureus ATCCBAA977, and St. pneumonia ATCC49619 were optimized. The results of this study showed that. The highest antibacterial activity was at 30 ° C after 7 days of incubation.
Furthermore, the best to produce antibacterial activity was under alkaline conditions (pH 8.5). Besides, the isolate didn't show antibacterial activity at the shaking incubator. This study showed that all organic solvents (ethyl-alcohol, methanol, chloroform, ethyl-acetate, and acetone) successfully extracted the antibacterial compound. Still, the compounds extracted by chloroform had the highest antibacterial activity. The MIC of the chloroform extract was against S. aureus ATCCBAA977. The study described the optimized condition for best S. globosus activity. The S. globosus showed a broad spectrum of antimicrobial activities against the test organisms. This opened further research investigations on the purification and structural characterization of the active compounds from the crude extract.