Infrared spectroscopy with multivariate analysis to interrogate the interaction of whole cells and secreted soluble exopolimeric substances of Pseudomonas veronii 2E with Cd(II), Cu(II) and Zn(II)

Abstract

Extracellular polymeric substances (EPS) are bacterial products associated to cell wall or secreted to the liquidmedia that form the framework of microbial mats. These EPS contain functional groups as carboxyl, amino, hydroxyl,phosphate and sulfhydryl, able to interact with cations. Thus, EPS may be considered natural detoxifyingcompounds of metal polluted waters and wastewaters. In this work Attenuated Total Reflectance-Fourier TransformInfrared spectroscopy (ATR-FTIR) in combination with multivariate analysis (Principal ComponentAnalysis-PCA-) were used to study the interaction of Cd(II), Cu(II) and Zn(II) and Pseudomonas veronii 2E cells,including bound EPS and cell wall, and its different soluble EPS fractions, previously characterized as Cd(II) ligandsof moderate strength. Amino groups present in exopolysaccharide fraction were responsible for Zn(II)and Cu(II) complexation, while carboxylates chelated Cd(II). In lipopolysaccharide fraction, phosphoryl and carboxylsites were involved in Cd(II) and Cu(II) binding, while Zn(II) interacted with amino groups. Similar resultswere obtained from cells.These studies confirmed that FTIR-PCA is a rapid analytical tool to provide valuable information regarding thefunctional groups in biomolecules related to metal interaction. Moreover, a discrimination and identification offunctional groups present in both EPS and cells that interacted with Cd(II), Zn(II) and Cu(II) was demonstrated.