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Isolation and antifungal and antioomycete activities of aerugine produced by Pseudomonas fluorescens strain MM-B16

Lee, J.Y., Moon, S.S., Hwang, B.K.
Applied and environmental microbiology 2003 v.69 no.4 pp. 2023-2031
Pseudomonas fluorescens, soil bacteria, isolation, mountain soils, forest soils, biological control, fungal antagonists, antifungal properties, antibiotics, chemical structure, ribosomal DNA, nucleotide sequences, Colletotrichum orbiculare, Phytophthora capsici, Pythium ultimum, plant pathogenic fungi, disease control, fungal diseases of plants, anthracnose, Capsicum annuum, peppers, Cucumis sativus, cucumbers
The bacterial strain MM-B16, which showed strong antifungal and antioomycete activity against some plant pathogens, was isolated from a mountain forest soil in Korea. Based on the physiological and biochemical characteristics and 16S ribosomal DNA sequence analysis, the bacterial strain MM-B16 was identical to Pseudomonas fluorescens. An antibiotic active against Colletotrichum orbiculare and Phytophthora capsici in vitro and in vivo was isolated from the culture filtrates of P. fluorescens strain MM-B16 using various chromatographic procedures. The molecular formula of the antibiotic was deduced to be C10H11NO2S (M+, m/z 209.0513) by analysis of electron impact mass spectral data. Based on the nuclear magnetic resonance and infrared spectral data, the antibiotic was confirmed to have the structure of a thiazoline derivative, aerugine [4-hydroxymethyl-2-(2-hydroxyphenyl)-2-thiazoline]. C. orbiculare, P. capsici, and Pythium ultimum were most sensitive to aerugine (MICs for these organisms were approximately 10 microgram ml-1). However, no antimicrobial activity was found against yeasts and bacteria even at concentrations of more than 100 microgram ml-1. Treatment with aerugine exhibited a significantly high protective activity against development of phytophthora disease on pepper and anthracnose on cucumber. However, the control efficacy of aerugine against the diseases was in general somewhat less than that of the commercial fungicides metalaxyl and chlorothalonil. This is the first study to isolate aerugine from P. fluorescens and demonstrate its in vitro and in vivo antifungal and antioomycete activities against C. orbiculare and P. capsici.