FIG. 3.

LC-MS spectra of B. holmesii supernatants from iron-depleted and iron-replete cultures. (A) LC-MS spectra of iron-depleted (−Fe) and iron-replete (+Fe) B. holmesii supernatants, depicting ions with m/z 405 (corresponding to alcaligin) and with retention times between 0 and 45 min. (B) Fragment ions detected after collisional activation (35% energy) of the peak from (A), with a retention time of 36.99 min. After measurement of the reference standard, the calibration deviated by approximately 1.5 mass units, explaining the difference in m/z values compared to those of the fragment ions as reported in reference 22. The nomenclature of fragment ions is according to that in reference 27.