| Summary: | 碩士 === 臺灣大學 === 植物病理與微生物學研究所 === 96 === Bacillus cereus C1L, an antagonistic bacterium, was originally isolated from the rhizosphere of Fomorsa lily. In order to identify the genes related to the antagonistic ability of B. cereus C1L, a transponson insertion mutant library was constructed. Totally, 850 mutants were obtained. Alternaria brassicicola and Alternaria longipes were used in mutant screening on potato dextrose agar and a mutant, M-902, with significant decrease on antifungal activity was selected. M-902 loses its inhibitory activity against mycelial growth of A. brassicicola, A. longipes, Botrytis cinerea, and Botrytis elliptica ; in addition, the culture supernatant of M-902 decreases spore germination rate. Sequence analysis revealed that the Tn917ac1 was inserted into a plasmid pC1L8 of B. cereus C1L wild-type strain. Southern blot analysis showed a band shift of pC1L8 of B. cereus M-902. The Tn917ac1 insertion site was located downstream a putative promoter of open reading frames-orf1 and orf2。These two ORFs may constitute a two-gene operon. In a complementay test using A. brassicicola as the test fungus, the vector containing predicted promoter, orf1 and orf2, or orf2 singly showed a partial recovery of the inhibition on conidial germination, but orf1 singly could not recover the inhibition on conidial germination. Thus, orf 2 related to antibiotic production of strain C1L was presumed.
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