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Open Access Open Badges Research article

The chemical-in-plug bacterial chemotaxis assay is prone to false positive responses

Jun Li2, Alvin C Go1, Mandy J Ward23* and Karen M Ottemann13*

Author affiliations

1 Department of Microbiology and Environmental Toxicology, UC Santa Cruz, Santa Cruz, 95064, USA

2 Department of Geography and Environmental Engineering, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA

3 Department of Earth Sciences, 3651 Trousdale Pkwy, Los Angeles, CA 90089, USA

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Citation and License

BMC Research Notes 2010, 3:77  doi:10.1186/1756-0500-3-77

Published: 16 March 2010



Chemical-in-plug assays are commonly used to study bacterial chemotaxis, sometimes in the absence of stringent controls.


We report that non-chemotactic and non-motile mutants in two distinct bacterial species (Shewanella oneidensis and Helicobacter pylori) show apparent zones of accumulation or clearing around test plugs containing potential attractants or repellents, respectively.


Our results suggest that the chemical-in-plug assay should be used with caution, that non-motile or non-chemotactic mutants should be employed as controls, and that results should be confirmed with other types of assays.