Pseudomonas putida adhesion to goethite: Studied by equilibrium adsorption, SEM, FTIR and ITC

Equilibrium adsorption along with scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and isothermal titration calorimetry (ITC) techniques were employed to investigate the adhesion of Pseudomonas putida on goethite. The adhesion isotherm revealed the high affinity of P. putida for goethite. The SEM analysis also showed a tight association between bacteria and mineral particles. Larger amounts of adhesion of bacteria on goethite were observed at pH lower than the isoelectric point (IEP) of goethite. The bacterial adhesion increased with increasing concentration of K+. The calorimetric results demonstrated that the P. putida–goethite adhesion was an exothermic process. The adhesion enthalpy increased with increasing pH and concentrations of electrolyte. The increase of the negative enthalpy with increment of temperature indicated that the bacteria–goethite adhesion was an enthalpy-driven process. Electrostatic interactions and hydrogen bonding were considered to contribute mainly to the adhesion of bacterial adhesion on goethite. The data obtained in this study would provide valuable information for a better understanding of the mechanisms of mineral–microorganism interactions in soil and associated environments.