A rifampicin-resistant ( rpoB ) mutation in Pseudomonas protegens Pf-5 strain leads to improved antifungal activity and elevated production of secondary metabolites

Ribosome engineering has proven to be a practical method for increasing antibiotic production, and is extensively applied to strain improvement in antibiotic production and activation of silent genes in several prokaryotes. In this study, ribosome engineering was used to improve production of bioactive secondary metabolites produced by Pseudomonas protegens Pf-5. Rifampicin-resistant mutants that bear the H531N in the β-subunit of RNA polymerase showed improved antifungal activity and morphological changes. The production of several secondary metabolites in R55 mutant was significantly improved using high-performance liquid chromatography (HPLC) analysis. Two antibiotics with antifungal activity, 2, 4-diacetylphloroglucinol (Phl) and pyoluteorin (Plt), which may contribute to the improved antifungal activity of the R55 mutant, were identified by mass spectrometer (MS) analysis.