The fate, transport and adhesion characteristics of microbes are of significant interest in restoration and maintenance of drinking water supplies, and as infectious agents from which drinking water supplies must be protected. This investigation examines the origins of observed differences in transport behavior of two different adhesion-deficient, gram-negative bacterial strains – DA001 & OY107 in a radial stagnation-point flow system. Measured surface characteristics (e.g. surface potential, electrostatic interaction chromatography, and hydrophobic interaction chromatography) indicate equivalent surface properties for these two strains. However, field scale and benchtop transport experiments demonstrate strongly contrasting transport behaviors for these two strains in porous media. Observation of these strains in the radial stagnation-point flow system provides directly-observed differences in their attachment detachment behaviors that may lead to better understanding of their contrasting transport behaviors despite their equivalent surface characteristics.