Research Into Amino Acid-derived Secondary Metabolites Of Bacillus Subtilis

The thesis mainly involves the isolation of a B.subtilis（TJU01W1）strain from Tianjin University,the identification of the strain based on 16S r DNA,the optimization of culture conditions,precursor-directed biosynthesis experiments,the isolation,purification and structure identification of its secondary metabolites,and the determination of their biological activities.As a result,nine compounds were isolated from this strain:3,6-dimethylpyrazin-2（1H）-one（1）,leuglycin（2）,C₁₃-surfactin（3）,C₁₄-surfactin（4）,C₁₅-surfactin（5）,3-Hydroxyacety-l-indole（6）,indole-3-carboxaldehyde（7）,1-acetyl-?-carboline（8）and pityriacitrin（9）.In addition,the incorporation of one to four 5,5,5-trifluoro-DL-leucines using precursor-directed biosynthesis into surfactin resulted in the production of new fluorinated surfactins.Antibacterial experiments showed:（1）The crude methanol extract of cultures supplemented with trifluoroleucine exhibited relatively strong antibacterial activity against Staphylococcus aureus ATCC 12600,Staphylococcus epidermidis ATCC14990,Moraxella catarrhalis ATCC 25238 and Penicillium chrysogenum ATCC10106,in comparison to similar extracts from cultures without added trifluoroleucine.（2）Surfactins C₁₃,C₁₄ and C₁₅ were active against Staphylococcus aureus ATCC12600（MIC=67μg/m L）,Staphylococcus epidermidis ATCC14990（MIC=67μg/m L）.The remaining compounds tested did not exhibit either antibacterial（MIC>133μg/m L）or antifungal activities（MIC>133μg/m L）.