(141b) Determining the Extent and Influence of Flagella, Injection Concentration, and Solution Chemistry In Salmonella Transport

This study focuses on the transport of Salmonella, a bacterial pathogen, and the extent to which mobility, cell injection concentration, and solution chemistry in groundwater. The goal was to determine how flagellar components, experimental solution chemistry and cell concentration affect its fate. For this purpose, Salmonella enterica subspecies enterica serovars Gallinarum (wild type, non-flagellated) and Typhimurium (wild type and dysfunctional flagellated mutant strain) were injected into a packed bed column with aquifer sand over a range of solution ionic strength (IS) and cell concentration simulating groundwater environments. Initial transport experiments conducted with non-flagellated Salmonella strains showed trends that cannot be explained with classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory alone (Derjaguin and Landau; 1941). Therefore, comprehensive cell surface characterization techniques including size, surface charge density, extracellular polymeric substances, electrophoretic mobility, and hydrophobicity analyses were conducted to explain observed transport trends. Electrophoretic mobility calculations, in agreement with titration analysis and column experiment results revealed that non-flagellated Salmonella was less electronegative than other previously studied non-pathogenic bacteria (Walker et al., 2004; Walker et al., 2005). Packed bed column experiments allow for calculation of transport distances and these distances were found to be up to 33 meters in low ionic strength conditions at our tested flow rate and injection concentration values. Results to be presented at the American Institute of Chemical Engineers (AIChE) 2008 Annual Meeting will include the relative transport behavior currently under investigation of flagellated and dysfunctional flagellated Salmonella spp. with the non-motile Salmonella strain. The findings of this study contribute to the understanding of fate and transport of important pathogens in groundwater and seek to establish the relative role of biological (flagellar components) and physicochemical (IS and concentration) phenomena.

References:

1. Derjaguin, B. V., and L. Landau. 1941. Acta Physicochim U.S.S.R. 14:300.

2. Walker, S. L., J. A. Redman, and M. Elimelech. 2004. Role of cell surface lipopolysaccharides in Escherichia coli K12 adhesion and transport. Langmuir 20:7736-7746.

3. Walker, S. L. 2005. The role of nutrient presence on the adhesion kinetics of Burkholderia cepacia G4g and ENV435g. Colloids and Surfaces B-Biointerfaces 45:181-188.