SUMMARY: Two iron-regulated compounds have been found in acidified ethyl acetate extracts from culture supernatants of and type-strains. Synthesis of both compounds paralleled iron-deficient growth, and was repressed in the presence of 100 μ;M-FeCl. Yields of these substances varied among different strains and attained maximum levels during stationary phase. Thin layer chromatographic analysis in five different solvent systems revealed that the slower-moving compound chromatographed as two distinct bands, and showed values and spectral properties similar to pyochelin. The faster-moving compound co-migrated as a single band with a standard of commercial salicylic acid in each of the chromatographic systems tested. Moreover, a molecule with an identical was also produced by CHA401, which is known to synthesize salicylic acid as the only siderophore during iron-limited growth. Spectrophotometric and spectrofluorometric titrations led to the identification of this iron-regulated compound as salicylic acid, in agreement with the structure deduced from H-NMR and mass spectroscopy. The identity of the siderophore azurechelin as salicylic acid was also conclusively demonstrated. Salicylic acid, like pyochelin and pyoverdin, promoted growth in an iron-depleted medium. These results are consistent with a putative siderophore activity for salicylic acid, i.e. azurechelin, as has been demonstrated for and Thus, salicylic acid is likely to act as a siderophore in more than one species belonging to the genus


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