Purification and Structural Analysis of the Effective Anti-TMV Compound ε-Poly-l-lysine Produced by Streptomyces ahygroscopicus

Abstract

Microbial secondary metabolites produced by actinomycetes are important natural products widely applied to control plant diseases. A variety of actinomycetes were isolated from soil samples collected from Tianzhu Mountain in Shenyang, China. A <i>Streptomyces</i> strain Shenyang Tianzhu (STZ) exhibits effective antiviral activity against Tobacco mosaic virus (TMV). The isolate was identified as <i>Streptomyces ahygroscopicus</i> based on its cultural, morphological, physiological, biochemical characteristics as well as the phylogenetic analysis using 16S rRNA sequences. To obtain the pure anti-TMV compound from <i>Streptomyces</i> STZ, the culture broth was subjected to Amberlite IRC-50 ion-exchange resin, SX-8 macroporous adsorption resin and Sephadex G-25 gel column chromatography. The purified active compound was confirmed to be ε-poly-l-lysine (ε-PL), with molecular mass in the range of 3454⁻4352 Da by structural analysis with infrared (IR), matrix-assisted laser desorption ionization-time-of-flight MS (MALDI-TOF), thin-layer chromatography (TLC) and high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR). The protective and curative effects of the purified compound ε-PL were tested and the results showed that the compound exhibited significant protective and curative activity against TMV. The potential application of ε-PL as an efficient anti-plant virus agent was expected.