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KMID : 0545120030130030415
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Journal of Microbiology and Biotechnology
2003 Volume.13 No. 3 p.415 ~ p.421
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Pyoverdin2112 of Pseudomonas fluorescens 2112 Inhibits Phytophthora capsici, a Red- Pepper Blight-Causing Fungus
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Lee ET
Lim SK/Nam DH/Khang YH/Kim SD
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Abstract
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A bacterium Pseudomonas fluorescens 2112 that is antagonistic against a red-pepper blight-causing fungus Phytophthora capsici was isolated from the local soil of Gyongju Korea. This strain formed an orange-colored clear halo zone on chrome azurol S (CAS) blue agar suggesting the production of a siderophore in addition to an antifungal antibiotic. The optimal culture conditions for siderophore production by P. fluorescens 2112 were 30-h cultivation at 25oC and pH 6.5 in King’s B medium. The presence of 20 mg/ml of Fe3+ ion or EDDHA promoted the production of siderophore in King’s B medium. The siderophore was purified from culture broth by CM-Sephadex C-25 and Sephadex G-25 column chromatographies. The UV spectra of the purified siderophore was the same as that of pyoverdins or pseudobactins. The molecular mass was 1958 Da determined by FAB-mass spectrometer and the amino acid composition analysis showed that the purified siderophore consisted of glycine/threonine/serine/glutamic acid/alanine/lysine with the molar ratio of 3:2:1:1:1:1. DL-Threo-b-hydroxyaspartic acid and Nd-hydroxyornithine two of the essential constituents of pyoverdin were also found. The purified siderophore pyoverdin showed strong in vitro and in vivo antagonistic activities against phytophthora blight-causing P. capsici. Especially in an in vivo pot test the siderophore protected red-pepper Capsicum annum L. very well from the attack of P. capsici. These results indicated that the purified siderophore of P. fluorescens 2112 played a critical role in the biocontrol of the red-pepper blight disease equivalent to treatment by P. fluorescens 2112 cells.
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