Cadmium-induced changes in the production of siderophores by a plant growth promoting strain of Pseudomonas fulva

The impact of increasing Cd2+ exposure on the quality and quantity of siderophores produced by a plant growth promoting Pseudomonas fulva strain was tested to gain insight into the degree of change. P. fulva was cultured in the increasing concentrations of Cd2+ (0, 0.5, 1.0, 2.0 mM). The secreted siderophores were separated by HPLC and characterized by UHPLC-QTOF/MS. In the presence of 2 mM Cd2+ synthesis of siderophores (hydroxamates, catecholates, phenolates) was mitigated compared to the treatments with lower concentrations of Cd2+ (0.5 and 1 mM). Increased synthesis of catecholates in 0.5 and 1 mM Cd2+ and of phenolates in 0.5-2 mM Cd2+ was revealed compared to the variant without Cd2+. Out of seven different hydroxamates, the secretion of ferrioxamine E was significantly decreased in the highest Cd2+ concentration. Two additional ferrioxamines, X2 and D2, were secreted independent of the presence or absence of Cd2+. Exposure to Cd2+ change the composition of siderophores secreted by P. fulva with selective promotion of catecholates and phenolates at the expense of hydroxamates. Successful adaptation in a Cd-contaminated soil in the frame of practical applications to promote phytoremediation can be assumed.