Full Length Research Paper

Antibacterial substance produced by Streptomyces sp. No. 87

Kanlayani Charoensopharat¹, Petcharat Thummabenjapone², Pisan Sirithorn² and Sompong Thammasirirak^1*

¹Department of Biochemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.

²Department of Plant Pathology, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand.

*Corresponding author. E-mail: somkly@kku.ac.th. Tel: +66-43-342911. Fax: +66-43-342911.

Accepted 7 March, 2008

An antimicrobial substance produced by Streptomyces sp. No. 87 was partially purified and studied for its antibacterial characteristics using the swab paper disc technique. The cell-free culture filtrate showed antibacterial activity against several species of pathogens including Gram-positive bacteria, i.e. Bacillus cereus ATCC 11778, B. subtilis TISTR 008, B. megaterium, Staphylococcus aureus, S. aureus ATCC 25923, and S. epidermidis and Gram-negative bacteria, i.e Klebsiella pneumoniae ATCC 27736, K. pneumoniae, Salmonella typhi ATCC 5784, Vibrio cholerae and Xanthomonas sp. 60% ammonium sulfate precipitation of the culture supernatant shows markedly antibacterial activity against B. cereus ATCC 11778. Then supernatant was purified by gel filtration chromatography with sephadex G-25 resin. Five peaks namely P1, P2, P3, P4 and P5 were obtained. Results indicate that P3 is the only peak possessing the antibacterial activity, therefore, the final purification of P3 was conducted using FPLC with a superdex 30 column. Only one peak, namely P3-1 retained the antibacterial activity. P3-1 showed that its activity was insensitive to proteolytic enzymes such as trypsin, pepsin and proteinase K. In addition, the activity of P3-1 could be observed temperatures of 50 -121^oC and no protein or polypeptide band was seen when P3-1 was analyzed by SDS-PAGE. These results suggest that P3-1 might not be proteinacious in nature. 

Key words: Antibacterial substance, characterization, purification, Streptomyces.