Pseudomonas fluorescens SBW25 produces furanomycin, a non-proteinogenic amino acid with selective antimicrobial properties

Background: Pseudomonas fluorescens SBW25 has been extensively studied because of its plant growth promoting properties and potential as a biocontrol agent. The genome of SBW25 has been sequenced, and among sequenced strains of pseudomonads, SBW25 appears to be most closely related to P. fluorescens WH6. In the authors' laboratories, WH6 was previously shown to produce and secrete 4-formylaminooxyvinylglycine (FVG), a non-proteinogenic amino acid with selective herbicidal and antimicrobial activity. Although SBW25 does not have the genetic capacity to produce FVG, we were interested in determining whether this pseudomonad might produce some other type of non-proteinogenic amino acid. Results: P. fluorescens SBW25 was found to produce and secrete a ninhydrin-reactive compound with selective antimicrobial properties. This compound was purified from SBW25 culture filtrate and identified as the non-proteinogenic amino acid L-furanomycin [2S,2'R,5'S)-2-amino-2-(5'methyl-2',5'-dihydrofuran-2'-yl)acetic acid]. Conclusions: The identification of furanomycin as a secondary metabolite of SBW25 is the first report of the production of furanomycin by a pseudomonad. This compound was known previously only as a natural product produced by a strain of Streptomyces. This report adds furanomycin to the small list of non-proteinogenic amino acids that have been identified as secondary products of pseudomonads. This study also extends the list of bacteria that are inhibited by furanomycin to include several plant pathogenic bacteria.