Pyochelin: novel structure of an iron-chelating growth promoter for Pseudomonas aeruginosa.

Pyochelin, an endogenous growth promoter that solubilizes ferric iron, has been isolated from Pseudomonas aeruginosa, including clinical strains. The structure of pyochelin has been assigned as 2-(2-o-hydroxyphenyl-2-thiazolin-4-yl)-3-methylthiazolidine-4-carboxylic acid and is of a different type from those previously assigned to siderophores (siderochromes) from bacteria. The assignment rests on 1H and 13C NMR data, high-resolution (including field desorption) mass spectrometry, and spectroscopic properties of synthetic model compounds. Pyochelin is presumed to be biosynthesized from salicylic acid and two moles of cysteine.