Interaction of Pb(II) and biofilm associated extracellular polymeric substances of a marine bacterium Pseudomonas pseudoalcaligenes NP103

Abstract

Three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy and attenuated total reflectance fourier-transformed infrared spectroscopy (ATR-FTIR) was used to evaluate the interaction of biofilm associated extracellular polymeric substances (EPS) of a marine bacterium Pseudomonas pseudoalcaligenes NP103 with lead [Pb(II)]. EEM fluorescence spectroscopic analysis revealed the presence of one protein-like fluorophore in the EPS of P. pseudoalcaligenes NP103. Stern-Volmer equation indicated the existence of only one binding site (n=0.789) in the EPS of P. pseudoalcaligenes NP103. The interaction of Pb(II) with EPS was spontaneous at room temperature (∆G=−2.78kJ/K/mol) having binding constant (Kb) of 2.59M−1. ATR-FTIR analysis asserted the involvement of various functional groups such as sulphydryl, phosphate and hydroxyl and amide groups of protein in Pb(II) binding. Scanning electron microscopy (SEM) and fluorescence microscopy analysis displayed reduced growth of biofilm with altered surface topology in Pb(II) supplemented medium. Energy dispersive X-ray spectroscopy (EDX) analysis revealed the entrapment of Pb in the EPS. Uronic acid, a characteristic functional group of biofilm, was observed in 1H NMR spectroscopy. The findings suggest that biofilm associated EPS are perfect organic ligands for Pb(II) complexation and may significantly augment the bioavailability of Pb(II) in the metal contaminated environment for subsequent sequestration.