Proteomic Analysis Reveals Proteins, Siderophores, and Exopolysaccharides Involved in Cd(II) Stress Response of the Heavy Metal–Tolerant <scp><i>Delftia lacustris</i></scp> B11CM Strain

Heavy metal (HM) pollution, such as cadmium, significantly impacts ecosystems and poses serious risks to human health. In soil, it reduces fertility and agricultural productivity. On the other hand, bacteria employ several tolerance mechanisms in response to HM exposure, including the production of siderophores, exopolysaccharides, proteins, and peptides. This study aimed to identify the possible molecular mechanisms involved in Cd(II) tolerance in the Delftia lacustris B11CM strain using nano LC/MS-MS proteomic analysis, siderophore and exopolysaccharide assays, protein and thiol quantification, and the comparison of protein profiles obtained by SDS-PAGE. The results demonstrated the presence of siderophores, an increase in the production of exopolysaccharides, and thiol-rich compounds. A total of 80 proteins were detected in the presence of cadmium, which are involved in catalytic activity, metalloproteins or proteins that bind to different molecules, and transporters. These proteins participate in metabolism and cellular processes, with most of them located in the plasma membrane. These molecules likely enable this bacterium to survive in cadmium-contaminated environments and are directly associated with tolerance mechanisms, highlighting the potential of this strain to be used as a bioinoculant with agronomic interest or for bioremediation.