A Multiweek Project Examining the Chemotactic Behavior of Tetrahymena in an Undergraduate Biology Laboratory †
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Authors:
Rachel Hongo1,
Robert T. Grammer1,
Christopher E. Barton1,*
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Received 02 April 2019 Accepted 16 January 2020 Published 28 February 2020
- ©2020 Author(s). Published by the American Society for Microbiology
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[open-access] This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial-NoDerivatives 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/ and https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode), which grants the public the nonexclusive right to copy, distribute, or display the published work.
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†Supplemental materials available at http://asmscience.org/jmbe
- *Corresponding author. Mailing address: Department of Biology, Belmont University, 1900 Belmont Boulevard, Nashville, TN 37212. Phone: 615-460-5714. E-mail: [email protected].
Abstract:
A multi-week laboratory project has been developed to incorporate elements of student investigation, chemotactic behavior of protists, and genetic effects on chemotactic activity of Tetrahymena. The chemotaxis assay is based on spectrophotometric detection of protist-induced light scattering as cells migrate into a density gradient containing a known attractant. The three-week project consists of an introductory chemotaxis assay, investigation of dose-response effects, and culminates with the exploration of a Tetrahymena genetic mutant with known defects in motility. Additionally, this project incorporates a microscopic investigation of cellular structure and swimming behavior of mutant and wild-type cells. Students have responded well to the nature of the project, displaying clear understanding of the mechanism of the assay as well as the response of the protists to environmental manipulation and the molecular defects in the mutant cells.
References & Citations
Supplemental Material
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Appendix 1: Week one student protocol, Appendix 2: Week two student protocol, Appendix 3: Week three student protocol, Appendix 4: Laboratory preparation instructions
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Abstract:
A multi-week laboratory project has been developed to incorporate elements of student investigation, chemotactic behavior of protists, and genetic effects on chemotactic activity of Tetrahymena. The chemotaxis assay is based on spectrophotometric detection of protist-induced light scattering as cells migrate into a density gradient containing a known attractant. The three-week project consists of an introductory chemotaxis assay, investigation of dose-response effects, and culminates with the exploration of a Tetrahymena genetic mutant with known defects in motility. Additionally, this project incorporates a microscopic investigation of cellular structure and swimming behavior of mutant and wild-type cells. Students have responded well to the nature of the project, displaying clear understanding of the mechanism of the assay as well as the response of the protists to environmental manipulation and the molecular defects in the mutant cells.

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Author and Article Information
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Received 02 April 2019 Accepted 16 January 2020 Published 28 February 2020
- ©2020 Author(s). Published by the American Society for Microbiology
-
[open-access] This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial-NoDerivatives 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/ and https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode), which grants the public the nonexclusive right to copy, distribute, or display the published work.
-
†Supplemental materials available at http://asmscience.org/jmbe
- *Corresponding author. Mailing address: Department of Biology, Belmont University, 1900 Belmont Boulevard, Nashville, TN 37212. Phone: 615-460-5714. E-mail: [email protected].
Figures

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FIGURE 1
Tetrahymena chemotaxis toward various concentrations of proteose peptone, a known chemoattractant. Students performed the described experiment at room temperature in a Genesys 20 spectrophotometer according to the instructions provided in the Week One student protocol (described in Appendix 1 ).

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FIGURE 2
Chemotaxis of Tetrahymena toward increasing concentrations of proteose peptone. Students carried out a chemotaxis assay utilizing Tetrahymena and increased concentrations of proteose peptone (described in Appendix 2 ). Results varied as to whether 4 mg/mL or 8 mg/mL gave the larger response, but 12 mg/mL consistently gave the poorest chemotaxis. Students were encouraged to discuss possible reasons for that effect.

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FIGURE 3
The effect of oad gene mutation on the chemotaxis of Tetrahymena. Student-generated data examining the chemotactic ability of oad mutants as compared with wild-type Tetrahymena cells (described in Appendix 3 ). Data show that cells lacking a functional oad gene display a significant decrease in their ability to migrate toward a chemoattractant in this assay.