Experimental Measurements of the Adsorption of Bacillus subtilis and Pseudomonas mendocina Onto Fe-Oxyhydroxide-Coated and Uncoated Quartz Grains

In this study, we compared the adsorption of the gram-positive bacterium Bacillus subtilis with adsorption of the gram-negative bacterium Pseudomonas mendocina onto Fe-oxyhydroxide-coated and uncoated quartz grains as a function of pH and bacteria: mineral mass ratio. We studied metabolically-inactive cells in order to focus on the initial bacterial attachment mechanisms. The data show that the presence of Fe-oxyhydroxide-coatings on quartz surfaces significantly enhances the adsorption of bacteria and that in general the extent of adsorption decreases with increasing pH and with decreasing bacteria: mineral mass ratio. B. subtilisadsorbs to a greater extent than does P. mendocina onto the surface of the Fe-coated quartz. The adsorption behavior appears to be controlled by the overall surface charge of both bacterial and mineral surfaces. We model the adsorption data using a semi-empirical chemical equilibrium model that accounts for the site speciation of the adsorbing surfaces. Models describing bacterial adsorption to Fe-oxyhydroxide-coated quartz can account for changes in pH and bacteria: mineral mass ratio using one set of equilibrium constants.