Effect of manure on Escherichia coli attachment to soil

Attachment of bacteria to soil is an important component of bacterial fate and transport. Escherichia coli are commonly used as indicators of fecal contamination in the environment. Despite the fact that E. coli are derived exclusively from feces or manure, effect of the presence of manure colloids on bacteria attachment to agricultural soils was never directly studied. The objective of this work was to evaluate the magnitude of the effect of manure on E. coli attachment to soil. Escherichia coli attachment to soil was studied in batch experiments with samples of loam and sandy clay loam topsoil that were taken in Pennsylvania and Maryland. Escherichia coli cells were added to the water-manure suspensions containing 0, 20, and 40 g L(-1) of filtered liquid bovine manure, which subsequently were equilibrated with air-dry sieved soil in different soil to suspension ratios. The Langmuir isotherm equation was fitted to data. Manure dramatically affected E. coli attachment to soil. Attachment isotherms were closer to linear without manure and were strongly nonlinear in the presence of manure. The maximum E. coli attachment occurred in the absence of manure. Increasing manure content generally resulted in decreased attachment.