Tetrahymena in the classroom

Identification and utilization of a mutated 60S ribosomal subunit coding gene as an effective and cost-efficient selection marker for Tetrahymena genetic manipulation

Since the onset of molecular biology, the ciliate Tetrahymena thermophila has been one of the most convenient single-celled model eukaryotes for genetics, biochemistry, and cell biology. Particularly, thanks to the availability of several different selection markers, it is possible to knock out or knock in genes at multiple genetic loci simultaneously in Tetrahymena, which makes it an excellent model ciliate for tackling complex regulatory mechanisms. Despite these selection markers are efficient for genetic manipulation, the costly drugs used for selection have highlighted the urgent demand for an additional cost-efficient and effective selection marker. Here, we found that a mutated 60S ribosomal subunit component, RPL36A, confers T. thermophila with cycloheximide resistance. On top of that, we developed a cycloheximide cassette and explored suitable transformation and selection conditions. Using the new cassette, we obtained both knockout and knock-in strains successfully at a relatively low cost. This study also provided the first evidence that a cycloheximide resistance gene can be engineered as a selection marker to completely delete a gene from the highly-polyploid somatic nucleus in Tetrahymena.

A Multiweek Project Examining the Chemotactic Behavior of Tetrahymena in an Undergraduate Biology Laboratory

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.

Classroom-Based Research Experiences to Support Underserved STEM Student Success: From Introductory Inquiry to Optogenetics in the Embryonic Chicken

In order to help overcome barriers to success for undergraduate STEM students from disadvantaged backgrounds, we developed two classroom-based research experiences (REs), Connecting Life (CL) and the Summer Research Institute (SRI). These REs were implemented over a two-year period (2014-2015) for regional community college students as part of the Southern Illinois Bridges to the Baccalaureate (SI Bridges) program. CL and SRI, broadly centered in biomedical sciences research, are designed to be offered in tandem. CL utilizes a guided inquiry approach with microscopy work-stations in experimental cell biology to experientially introduce research while building skills and confidence. CL serves as the gateway experience for the SRI, an intensive summer RE in which scholars engage in authentic research using modern technologies including optogenetics. We piloted the REs in year 1 (9 scholars) and made refinements in year 2 (10 scholars). Participants ("Bridges scholars") were enrolled full-time at one of two regional, rural community colleges, and came on-site to Southern Illinois University at Carbondale (SIUC) for the paid REs. Here we report the development, design and implementation of CL and the SRI, and report improved STEM research-related attitudes and aptitudes as a result of these experiences. Our findings suggest that guided inquiry with increasingly technical authentic research projects in a classroom-based and supportive learning community-style setting is a positive model for the transformation of underserved community college students into confident, motivated scientists with research-ready skills, and is likely translatable to other research novices.

Tetrahymena as a Unicellular Model Eukaryote: Genetic and Genomic Tools

Tetrahymena thermophila is a ciliate model organism whose study has led to important discoveries and insights into both conserved and divergent biological processes. In this review, we describe the tools for the use of Tetrahymena as a model eukaryote, including an overview of its life cycle, orientation to its evolutionary roots, and methodological approaches to forward and reverse genetics. Recent genomic tools have expanded Tetrahymena's utility as a genetic model system. With the unique advantages that Tetrahymena provide, we argue that it will continue to be a model organism of choice.

Introducing the concept of biocatalysis in the classroom: The conversion of cholesterol to provitamin D3

Biocatalysis is a fundamental concept in biotechnology. The topic integrates knowledge of several disciplines; therefore, it was included in the course "design and optimization of biological systems" which is offered in the biochemistry curricula. We selected the ciliate tetrahymena as an example of a eukaryotic system with potential for the biotransformation of sterol metabolites of industrial interest; in particular, we focused on the conversion of cholesterol to provitamin D_3. The students work with wild type and recombinant strains and learn how sterol pathways could be modified to obtain diverse sterol moieties. During the course the students identify and measure the concentration of sterols. They also search for related genes by bioinformatic analysis. Additionally, the students compare biotransformation rates, growing the ciliate in plate and in a bioreactor. Finally, they use fluorescence microscopy to localize an enzyme involved in biotransformation. The last day each team makes an oral presentation, explaining the results obtained and responds to a series of key questions posed by the teachers, which determine the final mark. In our experience, this course enables undergraduate students to become acquainted with the principles of biocatalysis as well as with standard and modern techniques, through a simple and robust laboratory exercise, using a biological system for the conversion of valuable pharmaceutical moieties. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(2):105-114, 2017.

Immediate dissemination of student discoveries to a model organism database enhances classroom-based research experiences

Use of inquiry-based research modules in the classroom has soared over recent years, largely in response to national calls for teaching that provides experience with scientific processes and methodologies. To increase the visibility of in-class studies among interested researchers and to strengthen their impact on student learning, we have extended the typical model of inquiry-based labs to include a means for targeted dissemination of student-generated discoveries. This initiative required: 1) creating a set of research-based lab activities with the potential to yield results that a particular scientific community would find useful and 2) developing a means for immediate sharing of student-generated results. Working toward these goals, we designed guides for course-based research aimed to fulfill the need for functional annotation of the Tetrahymena thermophila genome, and developed an interactive Web database that links directly to the official Tetrahymena Genome Database for immediate, targeted dissemination of student discoveries. This combination of research via the course modules and the opportunity for students to immediately "publish" their novel results on a Web database actively used by outside scientists culminated in a motivational tool that enhanced students' efforts to engage the scientific process and pursue additional research opportunities beyond the course.