Heavy metal-driven changes in the exometabolite profile of Bacillus velezensis S18

Anthropogenic heavy metal contamination of aquatic ecosystems results in the toxic effects on microorganisms and the disruption of microbial community structures. To adapt to toxic stress, microorganisms employ various detoxification mechanisms, one of which is the biosynthesis of siderophores. In this study, we analyzed the changes in the exometabolite profile of the Bacillus velezensis S18 strain grown in the presence of different concentrations of heavy metals. It was demonstrated that salts of CoCl2×6H2O, AlCl3, ZnSO4, MnSO4, NiSO4×7H2O, FeCl3×6H2O, CuSO4×5H2O and GaBr3 significantly reduced the production of catecholate and hydroxamate-type siderophores, with complete inhibition observed in the presence of Ni2+, Fe3+, and Cu2+. HPLC profiling of exometabolites was performed, and their iron-chelating activity was evaluated using the CAS assay. These findings highlight the potential application of the B. velezensis S18 strain in bioremediation processes and the synthesis of broad-spectrum biochelators.