Isolation and Characterization of Antibiotic from Streptomyces sp. from Red Sea-Port Sudan

Abstract

Bacterial resistance to antibiotics is growing up day by day in both community and hospital setting, increasing morbidity and mortality, the continuous development of bacterial resistance leading to an urgent requirement for new antibacterial compounds. This study was conducted during the period 2012-2016 to isolate and characterize antibacterial compounds from Streptomyces strains in Red Sea, Port Sudan. A total of fifty soil samples were collected from different depths in Red Sea, Port Sudan. Different culture media were used for the isolation of promising Streptomyces with antibacterial activities. The isolates were characterized by microbiological methods and confirmed by molecular techniques using both conventional and multiplex PCR. Antibacterial activity of the isolates were done by agar wells diffusion method and perpendicular streak method using Staphylococcus aureus and Escherichia coli as indicator organisms. The cultural conditions were optimized for the maximum growth and antibacterial activity with different physical and chemical conditions including; temperature, pH, incubation period, effect of nitrogen source, trace elements, light & dark. The extraction of antibacterial compound was done by ethyl acetate solvent then evaluated for antibacterial activities against test microorganisms. Thin layer chromatography (TLC) technique and gas chromatography-mass spectrometer (GC-MS) analysis were used to characterize the active compounds. The results revealed that 21 (43%) isolates were recovered as promising organisms. Identification of these isolates showed that 9/21 (48%) were Streptomyces spp. Sequencing of the PCR products were compared with Gen Bank database and showed that all identified isolates were related to the genus Streptomyces species with similarity ranged from (92% to 99%). Of the broad spectrum Streptomyces, two (PS1 and PS28) were chosen for production of antibacterial compounds. Study on optimization of cultural conditions for PS1 and PS28 revealed that maximum growth and antibacterial activities were obtained when grown in a medium having the following properties (gm./L); Soybean, 2.5; MgSO4.7H2O, 1.0; K2HPO4, 2.5; dissolved in Sea water, when adjust pH to 7.5, and incubated at 30°C for seven days. GC-MS characterization of the ethyl acetate crude extract showed 54 and 96 compounds from PS1 and PS28 respectively. Of them eight (n=8) and eleven (n=11) respectively were antibacterial compounds. This study concluded that Streptomyces isolates from the Port Sudan coast are promising sources for antibacterial compounds. Further investigations for antifungal, antiviral and antitumor compounds are required.