<jats:title>Abstract</jats:title><jats:p>From a <jats:italic>Pseudomonas</jats:italic> strain novel hydroxamate/carboxylate siderophores were isolated which were named ornibactins representing the modified tetrapeptide <jats:sc>L</jats:sc>‐Orn<jats:sup>1</jats:sup>(<jats:italic>N</jats:italic>δ‐OH,<jats:italic>N</jats:italic>δ‐acyl)‐<jats:sc>D</jats:sc>‐<jats:italic>threo</jats:italic>‐Asp(β‐OH)‐<jats:sc>L</jats:sc>‐Ser‐<jats:sc>L</jats:sc>‐Orn<jats:sup>4</jats:sup>(<jats:italic>N</jats:italic>δ‐OH,<jats:italic>N</jats:italic> δ‐formyl)‐1,4‐diaminobutane. The side‐chain amino function of Orn<jats:sup>1</jats:sup>(<jats:italic>N</jats:italic>δ‐OH,<jats:italic>N</jats:italic>δ‐acyl) is acylated by 3‐hydroxyoctanoic acid in the most lipophilic component of the microheterogeneous siderophore mixture. The structure elucidation was based on GC amino acid analysis, GC‐MS and electrospray mass spectrometry of the iron complex. The 3‐hydroxyoctanoic acid and the primary sequence were established on the basis of <jats:sup>1</jats:sup>H and inverse detected <jats:sup>13</jats:sup>C two‐dimensional NMR spectra (COSY, TOCSY, NOESY, HMQC, HMBC) of the gallium‐ornibactin‐F complex which allowed the complete assignment of all <jats:sup>1</jats:sup>H and <jats:sup>13</jats:sup>C signals.