Thailandenes, Cryptic Polyene Natural Products Isolated from Burkholderia thailandensis Using Phenotype-Guided Transposon Mutagenesis

ACS Chem Biol. 2020 May 15;15(5):1195-1203. doi: 10.1021/acschembio.9b00883. Epub 2020 Jan 2.

Abstract

Burkholderia thailandensis has emerged as a model organism for investigating the production and regulation of diverse secondary metabolites. Most of the biosynthetic gene clusters encoded in B. thailandensis are silent, motivating the development of new methods for accessing their products. In the current work, we add to the canon of available approaches using phenotype-guided transposon mutagenesis to characterize a silent biosynthetic gene cluster. Because secondary metabolite biosynthesis is often associated with phenotypic changes, we carried out random transposon mutagenesis followed by phenotypic inspection of the resulting colonies. Several mutants exhibited intense pigmentation and enhanced expression of an iterative type I polyketide synthase cluster that we term org. Disruptions of orgA, orgB, and orgC abolished the biosynthesis of the diffusible pigment, thus linking it to the org operon. Isolation and structural elucidation by HR-MS and 1D/2D NMR spectroscopy revealed three novel, cryptic metabolites, thailandene A-C. Thailandenes are linear formylated or acidic polyenes containing a combination of cis and trans double bonds. Variants A and B exhibited potent antibiotic activity against Staphylococcus aureus and Saccharomyces cerevisiae but not against Escherichia coli. One of the transposon mutants that exhibited an enhanced expression of org contained an insertion upstream of a σ54-dependent transcription factor. Closer inspection of the org operon uncovered a σ54 promoter consensus sequence upstream of orgA, providing clues regarding its regulation. Our results showcase the utility of phenotype-guided transposon mutagenesis in uncovering cryptic metabolites encoded in bacterial genomes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anti-Bacterial Agents / biosynthesis*
  • Anti-Bacterial Agents / isolation & purification
  • Biological Products / chemistry*
  • Biological Products / isolation & purification
  • Burkholderia / chemistry
  • Burkholderia / genetics*
  • DNA Transposable Elements
  • Escherichia coli / drug effects
  • Gene Expression Regulation, Bacterial / drug effects
  • Genome, Bacterial
  • Multigene Family
  • Mutagenesis
  • Phenotype
  • Polyenes / isolation & purification
  • Polyenes / metabolism*
  • Polyketide Synthases / metabolism
  • Saccharomyces cerevisiae / drug effects
  • Secondary Metabolism
  • Transcription Factors / metabolism

Substances

  • Anti-Bacterial Agents
  • Biological Products
  • DNA Transposable Elements
  • Polyenes
  • Transcription Factors
  • Polyketide Synthases

Supplementary concepts

  • Burkholderia thailandensis