Chenchen Qu, Shanshan Yang, Monika Mortimer, Ming Zhang, Jinzhao Chen Yichao Wu, Wenli Chen, Peng Cai, Qiaoyun Huang, Functional group diversity for the adsorption of lead(Pb) to bacterial cells and extracellular polymeric substances, Environmental Pollution, Volume 295, 15 February 2022, 118651
Highlights
- •Mono-/multi-carboxylic, phosphodiester, phosphonic and sulfhydryl sites were identified.
- •EXAFS and ITC noticed concentration, strain and EPS type dependent Pb coordination.
- •P. putida cells were richer in sulfhydryl and phosphodiester groups than B. subtilis.
- •Pb adsorption follow universal entropy increase and inner-sphere complexation mechanism.
Abstract
Bacteria and their secreted extracellular polymeric substances (EPS) are widely distributed in ecosystems and have high capacity for heavy metal immobilization. The knowledge about the molecular-level interactions with heavy metal ions is essential for predicting the behavior of heavy metals in natural and engineering systems. This comprehensive study using potentiometric titration, Fourier-transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC) and X-ray absorption fine structure (XAFS) was able to reveal the functional diversity and adsorptionBacteria and their secreted extracellular polymeric substances (EPS) are widely distributed in ecosystems and have high capacity for heavy metal immobilization. The knowledge about the molecular-level interactions with heavy metal ions is essential for predicting the behavior of heavy metals in natural and engineering systems. This comprehensive study using potentiometric titration, Fourier-transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC) and X-ray absorption fine structure (XAFS) was able to reveal the functional diversity and adsorption mechanisms for Pb onto bacteira and the EPS in greater detail than ever before. We identified mono-carboxylic, multi-carboxylic, phosphodiester, phosphonic and sulfhydryl sites and found the partitioning of Pb to these functional groups varied between gram-negative and gram-positive bacterial strains, the soluble and cell-bound EPS and Pb concentrations. The sulfhydryl and phosphodiester groups preferentially complexed with Pb in P. putida cells, while multifunctional carboxylic groups promoted Pb adsorption in B. subtilis cells and the protein fractions in EPS. Though the functional site diversity, the adsorption of Pb to organic ligands occurred spontaneously through a universal entropy increase and inner-sphere complexation mechanism. The functional group scale knowledge have implications for the modeling of heavy metal behavior in the environment and application of these biological resources.
