The role of phosphate in bacterial interaction with iron-coated surfaces

This study investigated the role of phosphate in the adhesion of bacteria (Staphylococcus aureus ATCC 10537) to iron-coated surfaces. Column experiments were performed at phosphate concentrations ranging from 0.0 to 2.0 mM. Bacterial breakthrough curves were obtained by monitoring effluent, and mass recovery and sticking efficiency were quantified from these curves. At phosphate concentrations between 0 and 0.5 mM, bacterial attachment to iron-coated sand decreased with increasing phosphate concentration (mass recovery increased from 14.0 to 86.3%), possibly due to charge modification of the coated sand from positive to negative by adsorbed phosphate ions. Between 0.5 and 2.0 mM, however, bacterial attachment increased with increasing phosphate concentration (mass recovery decreased from 86.3 to 41.3%), possibly due to compression of the electrical double layer between bacteria and phosphate-adsorbed/negatively charged surfaces by free phosphate ions. This study demonstrates that phosphate can play different roles in bacterial interaction with iron-coated surfaces depending on its concentration.