Isolation and characterization of a new hydroxamic acid from Pseudomonas mildenbergii

A low molecular weight hydroxamic acid was produced by Pseudomonas mildenbergii in iron-deficient media associated with green fluorescent peptides. The chemical structure of this hydroxamic acid has been investigated for comparison to known iron-binding siderophores. The hydroxamic acid was extracted from lyophilized culture media with ethanol and methanol and crystallized as the hydrochloride. The product had a molecular weight of 202.6 and an empirical formula of C9H11O2N X HCl and contained hydroxylamine nitrogen. The infrared, nuclear magnetic resonance, and mass spectral data suggested that the chemical structure was N-methylphenylacetohydroxamic acid. N-Methylphenylacetohydroxamic acid was synthesized, and its melting point, elemental analysis, and molecular weight were identical with those of the natural product. The compound chelated ferric iron, producing a distinctive iron chelate absorption band at 470 nm. Its relationship to the green fluorescent peptides is discussed.