A paper membrane filter assay for ciliate chemoattraction

A quantitative bioassay for ciliate chemoattraction based on the Boyden assay is described with the ciliates Tetrahymena thermophila and Tetrahymena pyriformis as test organisms. A chamber is separated into two compartments by a Whatman 3MM filter, and a suspension of starved cells (approximately 10(5) cells/ml) is placed in one compartment and a solution containing attractant in the other. The gradient of chemoattractant across the filter causes the cells to swim through the filter into the attractant-containing compartment where their appearance is determined by electronic cell counting. The assay described is convenient with a signal-to-noise ratio of approximately 10. It is shown here to work with the attractants proteose peptone and platelet-derived growth factor.