A targeted siderophore Sperbactin from Lysobacter enzymogenes OH11: Characterization and biocontrol application against rice bacterial diseases.

INTRODUCTION Lysobacter enzymogenes OH11 is widely recognized for its potent antagonistic activity against diverse plant pathogens, including bacteria, fungi, and oomycetes. However, the specific compound responsible for its activity against Gram-negative bacteria had remained unidentified.

Objectives

This study aimed to identify the specific anti-Gram-negative bacterial compound produced by OH11 and to evaluate its potential as a biocontrol agent.

Methods

Methods included MS/NMR for structure elucidation, antagonism/greenhouse/UV-vis assays for function evaluation, medium/precursor optimization for yield enhancement, and gene knockout/enzyme assays for biosynthetic pathway identification.

Results

The isolated compound was identified as a spermidine-containing siderophore, designated Sperbactin. Through broad-spectrum screening, Sperbactin was discovered to exert highly targeted antagonistic effects specifically against rice pathogens (Xanthomonas oryzae). In greenhouse trials, Sperbactin demonstrated remarkable efficacy against rice bacterial blight, achieving a disease control efficacy of 85.31%, which is comparable to conventional chemical agents. The Sperbactin-Fe(III) complex was found to have a 1:1 M ratio and displayed a high affinity for ferric iron, with an association constant (Ka) of 2.16 × 1029 M-1. Furthermore, the fermentation yield of Sperbactin was increased by 3.29-fold, reaching 290.46 ± 6.22 mg/L. spbB and spbD were identified as essential genes for Sperbactin biosynthesis.

Conclusion

This study identifies Sperbactin as a highly promising, narrow-spectrum biocontrol candidate for the targeted management of rice bacterial diseases. Its development offers a sustainable and eco-friendly alternative to chemical pesticides, supporting the advancement of sustainable agriculture.