The genome of P. fluorescens WH6 has been sequenced [13] and compared to other sequenced strains of P. fluorescens[5, 13]. Among sequenced strains of pseudomonads, these selleck screening library comparative genomic and phylogenetic analyses indicated that WH6 was most

closely related to SBW25. These two strains appear to represent a distinct CAL-101 manufacturer clade within the lineage that includes P. fluorescens A506 and BG33R [5]. These analyses have shown that 69% of P. fluorescens WH6 genes have an orthologous sequence in SBW25, and they share extensive long-range synteny [13]. Nonetheless, in spite of the overall similarity of the SBW25 genome to that of WH6, SBW25 lacks a gene cluster we have shown to be essential to the biosynthesis of FVG [14]. P. fluorescens SBW25 was first isolated from the leaf surface of a sugar beet plant [15]. Since then it has been used as a model organism for evolutionary and plant colonization studies [16–20]. SBW25 has also been extensively studied for its plant growth-promoting properties and its ability to protect peas from seedling damping-off caused by

the oomycete Pythium ultimatum[21]. The secondary metabolites known to be produced by SBW25 include pyoverdine siderophores [22] and a viscosin-like cyclic lipopeptide [23]. The latter compound exhibits zoosporicidal activity towards a different oomycete, Phytophthora infestans, but its primary role appears to be in biofilm formation and facilitating the surface selleck kinase inhibitor motility of SBW25 [23]. Although the P. fluorescens SBW25 genome does not contain the gene cluster we have found to be essential for FVG production, the overall similarity of the WH6 and SBW25 genomes attracted our interest in the latter strain and in the possibility that SBW25 might also

produce some type of non-proteinogenic amino acid. In the present study, we report that P. fluorescens SBW25 produces and secretes a ninhydrin-reactive compound that selectively inhibits the growth of several bacterial plant pathogens. This compound was purified from P. fluorescens SBW25 culture filtrates and identified as the amino acid L-furanomycin. To our knowledge, this is only the second report Protirelin of furanomycin production by a microbe and the first report of furanomycin production by a pseudomonad. Results Presence of ninhydrin-reactive compounds in P. fluorescens SBW25 culture filtrate As a preliminary test for the production of non-proteinogenic amino acids by P. fluorescens SBW25, and to compare SBW25 culture filtrates with filtrate from WH6, dried culture filtrates of SBW25 and WH6 were extracted with 90% ethanol. Aliquots of the concentrated extracts were fractionated by thin-layer chromatography (TLC) on cellulose and silica plates. The resulting chromatograms were then stained with ninhydrin (Figure 1). The extract of SBW25 culture filtrate yielded a single, strongly-staining, ninhydrin-reactive band on both cellulose and silica TLC plates.