ABSTRACTAttachment ofMycobacterium aviumsubsp.paratuberculosisto soil particles could increase their availability to farm animals, as well as influence the transportation ofM. aviumsubsp.paratuberculosisto water sources. To investigate the possibility of such attachment, we passed a known quantity ofM. aviumsubsp.paratuberculosisthrough chromatography columns packed with clay soil, sandy soil, pure silica, clay-silica mixture, or clay-silica complexes and measured the organisms recovered in the eluent using culture or quantitative PCR. Experiments were repeated using buffer at a range of pH levels with pure silica to investigate the effect of pH onM. aviumsubsp.paratuberculosisattachment. Linear mixed-model analyses were conducted to compare the proportional recovery ofM. aviumsubsp.paratuberculosisin the eluent between different substrates and pH levels. Of the organisms added to the columns, 83 to 100% were estimated to be retained in the columns after adjustment for those retained in empty control columns. The proportions recovered were significantly different across different substrates, with the retention being significantly greater (P< 0.05) in pure substrates (silica and clay-silica complexes) than in soil substrates (clay soil and sandy soil). However, there were no significant differences in the retention ofM. aviumsubsp.paratuberculosisbetween silica and clay-silica complexes or between clay soil and sandy soil. The proportion retained decreased with increasing pH in one of the experiments, indicating greater adsorption ofM. aviumsubsp.paratuberculosisto soil particles at an acidic pH (P< 0.05). The results suggest that under experimental conditionsM. aviumsubsp.paratuberculosisadsorbs to a range of soil particles, and this attachment is influenced by soil pH.