Bacterial attachment in porous media

Abstract

Colloid filtration theory was utilized to estimate the sticking coefficient (α) of bacteria in filter media. Determination of bacterial cell numbers was facilitated by incorporation of [³H] leucine into cells prior to filtration. Large changes in retention of bacteria within porous material correlated with different stages in the bacterial growth cycle. This was due primarily to changes in cell size and not due to a change in α. The effects of ionic strength, pH, nutrient status, surfactant concentration and filter material on α were also evaluated. Various filtration models predicted similar trends in the magnitude of bacterial α with changes in experimental conditions. Experiments were performed with two gram negative and one gram positive bacterial species, Pseudomonas fluorescens, Pseudomonas JS6, and Bacillus pumilus. Small reductions in α were observed in cultures that were carbon-limited. Oxygen limitation produced no change in alpha. Bacterial α's were a function of ionic strength and filter material.