Fig. 1. Structures of the icosalides, identification of the NRPS-encoding gene responsible for icosalide biosynthesis in B. gladioli BCC0238 and phylogenetic comparison of the recA sequence amplified from total DNA of the Aureobasidium sp. originally reported to produce icosalide A1 with various Burkholderia species. (A) Structures of icosalides A1 (1), A2 (2) and B (3). (B) Schematic representation of the ∼500 kDa NRPS encoded by the ∼15 kb icoA gene. Domain abbreviations are as follows: C, condensation; A, adenylation; PCP, peptidyl carrier protein; TE, thioesterase. (C) Extracted ion chromatogram at m/z 713.46 ± 0.02, corresponding to [M + H]⁺ for icosalide A1, from LC-MS analyses of extracts of agar-grown cultures of B. gladioli BCC0238 (top) and B. gladioli BCC0238 ΩicoA, in which the NRPS-encoding gene has been disrupted (bottom). (D). Phylogenetic comparison of the recA sequence amplified from the total DNA extract of Aureobasidium sp. MSX 59166 (labelled ‘icosalide producer’) with recA sequences from 24 representative Burkholderia species, showing that the fungus-associated bacterium clades with Burkholderia gladioli. The scale bar indicates the number of substitutions per site.