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Poster: Biology & Disease Mgmt: Biological Control


Functional analyses of the ribosomal and non-ribosomal processed antimicrobial peptides produced by biocontrol bacterium Bacillus pumilus PMB102
W. DENG (1), J. Wu (1), J. Huang (1) (1) National Chung Hsing University, Taiwan

Many Bacillus spp. are beneficial bacteria with potential applications in the integrated management of plant diseases, and the efficacy of biocontrol is mainly determined by the production of secondary metabolites, e. g. the ribosomal processed lantipeptides and non-ribosomal processed cyclic lipopeptides (CLPs). In this study, the biocontrol agent B. pumilus PMB102 was shown to reduce tomato Fusarium wilt disease in hydroponic seedling assays. Annotation of the draft genome identified one lantipeptide and two CLPs, surfactin and plipastatin (fengycin family), biosynthetic gene clusters. Partially purified proteins from the lantipeptide-containing culture filtrate were resolved by electrophoresis and assayed for antibacterial activity by overlay assays, and one small polypeptide was identified to inhibit the growth of B. cereus and B. mycoides. The culture filtrates containing CLPs were extracted by n-butanol and fractionated by C18 SPE column. The eluted fractions were resolved by TLC and assayed for antifungal activity by the overlay assays to show that the compounds sharing the same Rf value of fengycin could inhibit the mycelial growth of Alternaria brassicicola. The chemical compositions of the abovementioned antimicrobial compounds will be further verified by mass spectrometry. The expression of defense-associated genes will also be monitored to determine if the plant defense responses against fungal pathogens are modulated by the biocontrol bacterium PMB102.