Mechanisms of adhesion of Paenibacillus polymyxa onto hematite, corundum and quartz

Abstract

Adhesion of bacteria onto solid surfaces is a necessary event in nature for the utilization of inorganic and organic values and for the enhanced growth of bacteria. Interactions between Paenibacillus polymyxa, with different minerals such as hematite, corundum and quartz are examined in this work in the light of Derjaguin, Landau, Verwey and Overbeek theory, popularly known as DLVO theory and possible chemical interactions. The adhesion process is normally controlled initially by physicochemical interactions between cells and mineral substrates and subsequently by the production of extra cellular polymers to make the attachment stronger. From this study, it is clear that maximum adsorption of cells on hematite and corundum occurs at a pH below the isoelectric point, whereas in the case of quartz the adsorption of cells remained almost constant in the entire pH range studied. From adhesion tests, it is also clear that the above bacteria adsorb preferentially on hematite and corundum than on quartz. It is obvious from the interaction energy calculations that the columbic forces play a major role in the interaction of P. polymyxa with hematite, corundum and quartz. Although the columbic forces do play such a role, it is evident from the Fourier Transform Infrared Spectroscopy (FTIR) results that other forces such as chemical forces are also involved simultaneously.