Abstract Detail

Education and Outreach

Hallen-Adams, Heather [1].

Gotta catch 'em all: Yeast isolation, identification, and competition lab.

I teach a three credit, upper-level (juniors, seniors, and graduate students) elective class, “Molds and Mycotoxins”, which normally meets as two one hour lectures and one three hour lab per week. This multi-component lab takes place over 2-3 weeks. Before the lab exercises began, students are asked to capture a yeast and given suggestions for doing so (common methods involve exposing fruit juice at room temperature, or leaving fruit in water with or without sugar, until either liquid is turbid and bubbling). We plate the yeasts on CHROMagar Candida, a chromogenic medium that gives a first approximation of yeast diversity, and each student restreaks any colonies of differing colors to obtain pure cultures. Pure cultures are used to inoculate API 20 C AUX test strips to determine physiological profiles; simultaneously, students use a simple DNA miniprep to isolate DNA and perform ITS PCR. PCR products are subject to Sanger sequencing and the students do a BLAST search to identify their yeasts, and compare the results with the physiological profiles. Finally, in the heavily anticipated “yeast fights”, each culture is prepared to 1.5 x 10⁶ cfu/mL and 1 mL is added to 15 mL liquid methylene blue agar (pH 5.0) for seeded agar plate assays. Once the agar has solidified, each other yeast is streaked across each seeded methylene blue plate. Zones of clearing around a streak indicate killer activity. Portions of these labs can be incorporated into other classes; a colleague did the identification, profiling, and yeast fights portion in a microbiology class using yeasts they obtained from student-derived sourdough cultures, and there has been talk of championship battles between the winning yeasts from different classes.

1 - University of Nebraska-Lincoln, Food Science and Technology, 1901 N 21st St, 252 Food Innovation Center, Lincoln, NE, 68588, USA

Keywords:
teaching
Killer yeasts
Lab exercise.

Presentation Type: Oral Paper
Session: ED3, Education & Outreach III: Teaching tools, Laboratories and Research Experiences
Location: /
Date: Wednesday, July 21st, 2021
Time: 2:15 PM(EDT)
Number: ED3006
Abstract ID:392
Candidate for Awards:None