Extracellular proteins enhance Cupriavidus pauculus nickel tolerance and cell aggregate formation

Heavy metal-resistant bacteria secrete extracellular proteins (e-PNs). However, the role of e-PNs in heavy metal resistance remains elusive. Here Fourier Transform Infrared Spectroscopy implied that N-H, C = O and NH₂-R played a crucial role in the adsorption and resistance of Ni²⁺ in the model organism Cuprividus pauculus 1490 (C. pauculus). Proteinase K treatment reduced Ni²⁺ resistance of C. pauculus underlining the essential role of e-PNs. Further three-dimension excitation-emission matrix fluorescence spectroscopy analysis demonstrated that tryptophan proteins as part of the e-PNs increased significantly with Ni²⁺ treatment. Proteomic and quantitative real-time polymerase chain reaction data indicated that major changes were induced in the metabolism of C. pauculus in response to Ni²⁺. Among those lipopolysaccharide biosynthesis, general secretion pathways, Ni²⁺-affiliated transporters and multidrug efflux play an essential role in Ni²⁺ resistance. Altogether the results provide a conceptual model for comprehending how e-PNs contribute to bacterial resistance and adsorption of Ni²⁺.