Figure 2. A B. pseudomallei 1710b malleobactin and pyochelin deficient double mutant exhibits siderophore activity.

A. Burkholderia GBrowse map of the B. pseudomallei 1710b pyochelin synthesis and uptake gene cluster [62]. Gene names are labeled. Dashed lines bordered by vertical solid black lines indicate the extents of deletions. B. Detection of apo-pyochelin in the culture supernatant of pyochelin synthesis gene cluster mutants by mass spectrometry. TSBFC overnight cultures were filtered through 0.2 µM membranes, acidified and extracted with ethyl acetate. Extracts were dried under N₂ and suspended in methanol. 5 µl samples were injected to detect the 325.068 M+H apo-pyochelin ion. The apo-pyochelin ion is indicated with arrows and isotope distribution ions are labeled. Note the different intensity scales in the top and bottom panels. C. To illustrate the presence of residual siderophore activity in Δ141-kb ΔPCH mutants, 5 µl samples from iron-limited TSBFC overnight cultures were spotted onto CAS agar plates and incubated at 37°C for 4 days prior to photographing.